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| Hariharan V, Murty B and Phanikumar G (2024), "Interface response functions for multicomponent alloy solidification - an application to additive manufacturing", Computational Materials Science. Vol. 231, pp. 112565. |
| Abstract: The near-rapid solidification conditions during additive manufacturing can lead to selection of non-equilibrium phases. Sharp interface models via interface response functions have been used earlier to explain the microstructure selection under such solidification conditions. However, most of the sharp interface models assume linear superposition of contributions of alloying elements without considering the non-linearity associated with the phase diagram. In this report, both planar and dendritic Calphad coupled sharp interface models have been implemented and used to explain the growth-controlled phase selection observed at high solidification velocities relevant to additive manufacturing. The implemented model predicted the growth-controlled phase selection in multicomponent alloys, which the other models with linear phase diagram could not. These models are calculated for different steels and the results are compared with experimental observations. |
BibTeX:
@article{Hariharan2024,
author = {Hariharan, V.S. and Murty, B.S. and Gandham Phanikumar},
title = {Interface response functions for multicomponent alloy solidification - an application to additive manufacturing},
journal = {Computational Materials Science},
year = {2024},
volume = {231},
pages = {112565},
url = {https://www.sciencedirect.com/science/article/pii/S0927025623005591},
doi = {10.1016/j.commatsci.2023.112565}
}
|
| Hariharan V, Kaushik R, Murty B and Phanikumar G (2024), "Effect of laser scan rotation on the microstructure and mechanical properties of laser powder bed fused Haynes 282", Materialia. Vol. 33, pp. 101992. |
| Abstract: Haynes 282 is a weldable, gamma-prime strengthened Ni-based superalloy and is a suitable candidate for aerospace and power-generation applications. Laser powder bed fusion (LPBF) of Haynes 282 is gaining attention recently due to its superior mechanical properties than its conventional counterparts. In spite of the superior mechanical properties, there are significant challenges concerning crystallographic anisotropy. One of the critical but less studied parameters that influence crystallographic anisotropy is the laser scan rotation angle. This study investigates the effect of laser scan rotation angle on the microstructure and subsequently on the mechanical properties. The samples fabricated with 90° scan rotation exhibited stronger texture while the samples with 137° rotation had weaker texture than samples with 67°. Further, three-dimensional Finite difference-Monte Carlo simulations were performed to understand the microstructure evolution with varying process parameters. The experimental and simulated microstructures are quantitatively compared using 2-point correlations. The texture and grain morphology evolution are explained based on melt pool morphology and microstructure simulations. Mechanical properties of as-built and aged samples are estimated using theoretical models and agree well with the experimental results. |
BibTeX:
@article{Hariharan2024a,
author = {Hariharan, V.S. and Ramit Kaushik and Murty, B.S. and Gandham Phanikumar},
title = {Effect of laser scan rotation on the microstructure and mechanical properties of laser powder bed fused Haynes 282},
journal = {Materialia},
year = {2024},
volume = {33},
pages = {101992},
url = {https://www.sciencedirect.com/science/article/pii/S2589152923003198},
doi = {10.1016/j.mtla.2023.101992}
}
|
| Hussain U, Swaminathan N and Phanikumar G (2024), "Numerical Voltammetry of Phase Separating Materials Using Phase Field Modeling", Journal of The Electrochemical Society. Vol. 171, pp. 070502. |
| Abstract: Higher capacity materials, such as Si and Sn are known to have phase separating behavior during the (de)lithiation. While initial models for lithiation in graphite electrode were based on single phase diffusion, with the introduction of Si and Sn, disposition of the models has shifted to the two-phase diffusion. It is important to understand the interaction of various phenomenon in materials which show phase change during (dis)charging cycles. In this work, we present a phase field model to simulate two-phase lithiation. This model is used to study the electrochemical response of the system by conducting numerical voltammetry. The main goal of this effort is to highlight the difference in electrochemical response occurring during single-phase diffusion and two-phase diffusion and explain the ensuing physics. Furthermore, effect of elasticity which governs the phase-change process and also alters corresponding voltammograms is also studied in detail. The voltammograms show clear shift in current peaks' size and position for the changing diffusion behavior. Also as elasticity affects the two-phase diffusion, change in nucleation timing and diffusion rate are visible in voltammograms. Additionally, it is also observed how elasticity can cease the phase separation behavior and voltammogram for two-phase diffusion can become identical to single-phase diffusion. |
BibTeX:
@article{Hussain2024,
author = {Umair Hussain and Narasimhan Swaminathan and Gandham Phanikumar},
title = {Numerical Voltammetry of Phase Separating Materials Using Phase Field Modeling},
journal = {Journal of The Electrochemical Society},
year = {2024},
volume = {171},
pages = {070502},
url = {https://iopscience.iop.org/article/10.1149/1945-7111/ad59cc/meta},
doi = {10.1149/1945-7111/ad59cc}
}
|
| Hussain U, Swaminathan N and Phanikumar G (2024), "Voltammetric Study of Phase Separating Anode Materials in Li-Ion Battery Using Phase Field Model", ECS Meeting Abstracts. Vol. MA2024-01, pp. 296. |
| Abstract: The increasing demand for higher energy capacity in lithium-ion batteries has underscored the significance of modeling lithiation with alternative electrode materials, such as silicon (Si) and tin (Sn). This research addresses the need for comprehensive insights into the (dis)charging process, particularly focusing on the intricate phase transformations in the anode. Phase-field modeling has proven effective in capturing these transformations [2], revealing volumetric deformations of up to 300% during (dis)charging cycles [1]. Unfortunately, these deformations compromise material integrity, leading to reduced battery cycle life and reliability. To address these challenges, our work presents a novel framework for modeling lithiation in materials exhibiting two-phase diffusion using phase field modeling. Unlike previous models limited to single-phase diffusion, our framework provides a more realistic representation of the diffusion process. This realism is achieved by incorporating the time-dependent voltage applied to the anode, a crucial factor in understanding the electrochemical response during lithiation [3]. Furthermore, we leverage the currents generated during the lithiation and delithiation processes to conduct a comprehensive voltammetric study. This study goes beyond existing research by considering the impact of phase separation on the currents developed during Li-ion battery operation. Our findings aim to contribute valuable insights into optimizing battery performance and addressing challenges associated with phase transformations, ultimately advancing the development of high-capacity anodes for lithium-ion batteries.</td> </tr> |
BibTeX:
@article{Hussain2024a,
author = {Umair Hussain and Narasimhan Swaminathan and Gandham Phanikumar},
title = {Voltammetric Study of Phase Separating Anode Materials in Li-Ion Battery Using Phase Field Model},
journal = {ECS Meeting Abstracts},
year = {2024},
volume = {MA2024-01},
pages = {296},
doi = {10.1149/MA2024-012296mtgabs}
}
|
| Mangalarapu TB, Kumar S, Ramakrishna M, Phanikumar G and Koppoju S (2024), "Effect of Initial Powder Condition on Precipitation Behavior in Cold Sprayed Al7075 Alloy Coatings", Journal of Thermal Spray Technology. |
| Abstract: This study explores the potential of cold spray technology for repairing high-strength Al7075 alloy components, particularly in the aerospace industry. The gas-atomized powder contains a dendritic cell structure with solutes segregated at the dendritic cell boundaries. Thus, direct aging of atomized powder fails to induce the formation of strengthened precipitates. Therefore, the effect of different powder pre-treatments on the deposition efficiency, microstructure, and aging behavior of the coatings was investigated. Cold spray coatings were deposited using as-received powder, solutionized, and solutionized + aged powders, revealing a significant improvement in thickness for coatings obtained using solutionized (110%) and solutionized + aged (80%) powders compared to the coating from the as-received atomized powder. Further, coatings deposited using as-received, solutionized, and solutionized + aged powders, were aged at 120 °C for various durations and the aging response of different coatings were studied. Microstructural studies revealed that gas-atomized powders exhibited dendritic structures with segregated solutes. Solutionizing eliminated the dendritic features, promoting deposition efficiency upon cold spraying. Aging of the coating from the solutionized powder led to the formation of ultrafine η' precipitates (29 ± 8 nm length, 2 ± 1 nm diameter) at peak-aged condition (after 8 h). These findings demonstrate the effectiveness of powder pre-treatment in tailoring the microstructure and deposition behavior of cold-sprayed Al7075 coatings, offering a promising approach for repair applications. |
BibTeX:
@article{Mangalarapu2024,
author = {Tarun Babu Mangalarapu and Kumar, S and Ramakrishna, M and Gandham Phanikumar and Suresh Koppoju},
title = {Effect of Initial Powder Condition on Precipitation Behavior in Cold Sprayed Al7075 Alloy Coatings},
journal = {Journal of Thermal Spray Technology},
year = {2024},
url = {https://link.springer.com/article/10.1007/s11666-024-01811-6},
doi = {10.1007/s11666-024-01811-6}
}
|
| Singh UP, Shukla A, Swaminathan S and Phanikumar G (2024), "Effect of build orientations on residual stress, microstructure, and mechanical properties of additively manufactured alloy-718 components", Journal of Manufacturing Processes. Vol. 113, pp. 1-15. |
| Abstract: During the laser powder bed fusion(L-PBF) process, the rapid solidification conditions coupled with repeated heating and cooling cycles constrain the design potential and printability of complex-shaped structures, especially for part-scale components. Process-induced residual stress, porosity, and crystallographic texture are the most challenging obstacles when designing quality components using this process. These defects also have a detrimental impact on the quality and structural durability of the deposited parts. To comprehend the coupled effect of these determinants on the mechanical performance of various orientated components, we perform a sequentially coupled thermo-mechanical simulation to obtain the residual stress evolution during the deposition as well as on printed coupons after the extraction of the support structure. Simulated outcomes have been verified using X-ray diffraction, and there is a good convergence between simulated and experimental values with a 10% maximum difference. X-ray tomography and Electron back scattered diffraction(EBSD) techniques were utilized to quantify the process-induced porosity(distribution and size) and crystallographic texture in the solidified component, respectively. The mechanical performance of the deposited components was evaluated using uniaxial tensile tests. The cracking behavior in fractured samples was studied using SEM-based fractography. Due to more number of repeated thermal cycles, the vertically deposited sample had higher residual stress, larger grains, and thus lower strength. |
BibTeX:
@article{Uday2024,
author = {Uday Pratap Singh and Abhishek Shukla and Srinivasan Swaminathan and Gandham Phanikumar},
title = {Effect of build orientations on residual stress, microstructure, and mechanical properties of additively manufactured alloy-718 components},
journal = {Journal of Manufacturing Processes},
year = {2024},
volume = {113},
pages = {1--15},
url = {https://www.sciencedirect.com/science/article/pii/S1526612524000641},
doi = {10.1016/j.jmapro.2024.01.047}
}
|
| Arunkumar K, Bakshi S, Phanikumar G and Rao T (2023), "Study of flow and heat transfer in high pressure die casting cooling channel", Metallurgical and Materials Transactions B. Vol. 54, pp. 1665-1674. |
| Abstract: High-pressure die casting (HPDC) is a widely used process with short cycle times to manufacture complex shapes of aluminium castings for the automotive industry. Most of the die casting companies use specialized commercial software to simulate molten metal filling and solidification. This approach works satisfactorily and is industrially accepted for defect prediction capability. Die cooling is an effective technique to reduce internal porosity in die cast components. But die cooling process is not completely captured in the approach used in the casting simulations. This often resulted in false positives in the defect predictions. One of the main reasons for the lack of precision in simulation is the uncertainty in assigning the boundary conditions such as heat transfer coefficients (HTC) for the die cooling channel. In this study, a coupled simulation strategy was developed to determine accurate HTC values of the die cooling channel. The computational domain was divided into two sub-domains, i.e., casting zone and die cooling zone. Two different industrially accepted simulation tools were used: (a) for casting simulation and (b) for turbulent fluid flow and heat transfer simulation in the cooling channel. A series of iterations were performed by exchanging information at the interface between the two sub-domains till the convergence was achieved. Experiments were also conducted with a thermocouple inserted in the die and the actual die temperature readings were measured. The converged simulation results agreed well with the experimental measurements. Also, the influence of flow rate on HTC was studied by conducting experiments with two different flow rates and the castings produced were analyzed with the help of CT scan analysis, micro-structure evaluation and thermal imaging. The obtained results demonstrated the efficacy of the method adopted in prescribing the values of heat transfer conditions in casting simulations. With the coupled simulation approach developed in this work, parametric studies were conducted to maximize the heat removal rate from a given die, for different flow velocities, nozzle diameters, cooling hole diameters and nozzle-to-surface spacings. |
BibTeX:
@article{Arunkumar2023,
author = {Arunkumar, K and Bakshi, Shamit and Phanikumar, Gandham and Rao, TVLN},
title = {Study of flow and heat transfer in high pressure die casting cooling channel},
journal = {Metallurgical and Materials Transactions B},
year = {2023},
volume = {54},
pages = {1665--1674},
url = {https://link.springer.com/article/10.1007/s11663-023-02785-6},
doi = {10.1007/s11663-023-02785-6}
}
|
| Bansal A, Kumar P, Yadav S, Hariharan V, Rahul MR and Phanikumar G (2023), "Accelerated design of high entropy alloys by integrating high throughput calculation and machine learning", Journal of Alloys and Compounds. Vol. 960, pp. 170543. |
| Abstract: Designing high entropy alloys (HEAs) from a large compositional space is challenging. The design process is accelerated by integrating computational techniques. The current study developed a framework for the accelerated identification of phases in HEAs by integrating high throughput calculations and machine learning (ML). The 19968 composition information was generated using high throughput CALculation of PHAse Diagrams (CALPHAD) calculations and used as a dataset for the machine learning algorithms. The Synthetic Minority Over-sampling Technique (SMOTE) makes unbiased data, and multiple machine learning algorithms are trained and compared. The Support Vector Machine (SVM) and Artificial Neural Network (NN) show test accuracy of ∼99%. The trained algorithm was used to predict phases in ternary, quaternary and quinary systems. The experimental comparison confirms that the algorithms successfully predicted the phase transitions in HEAs with respect to varying compositions. The developed framework can be adopted for designing new materials. |
BibTeX:
@article{Bansal2023,
author = {Adarsh Bansal and Pankaj Kumar and Shubham Yadav and VS Hariharan and Rahul MR and Gandham Phanikumar},
title = {Accelerated design of high entropy alloys by integrating high throughput calculation and machine learning},
journal = {Journal of Alloys and Compounds},
year = {2023},
volume = {960},
pages = {170543},
url = {https://www.sciencedirect.com/science/article/pii/S0925838823018467},
doi = {10.1016/j.jallcom.2023.170543}
}
|
| Beniwal D, Shivam V, Palasyuk O, Kramer MJ, Phanikumar G and Ray PK (2023), "EDS-PhaSe: Phase segmentation and analysis from EDS elemental map images using markers of elemental segregation", Metallography, Microstructure and Analysis. |
| Abstract: Scanning electron microscopy (SEM), combined with energy-dispersive spectroscopy (EDS), is an extensively used technique for in-depth microstructural analysis. Here, we present the EDS-Phase Segmentation (EDS-PhaSe) tool that enables phase segmentation and phase analysis using the EDS elemental map images. It converts the EDS map images into estimated composition maps for calculating markers of selective elemental redistribution in the scanned area and creates a phase-segmented micrograph while providing approximate fraction and composition of each identified phase. EDS-PhaSe offers two unique advantages. Firstly, it enables the direct processing of EDS elemental map images without requiring any raw or proprietary data/software, thereby allowing the analysis of EDS results available in the published literature as images. Secondly, it enables segmentation and analysis of phases even when the phase contrast is missing in backscattered micrographs, assisting in correlating the XRD and SEM-EDS data as shown in this work for a AlCoCrFeNi high-entropy alloy. |
BibTeX:
@article{Beniwal2023,
author = {Dishant Beniwal and Vikas Shivam and Olena Palasyuk and Matthew J Kramer and Gandham Phanikumar and Pratik K Ray},
title = {EDS-PhaSe: Phase segmentation and analysis from EDS elemental map images using markers of elemental segregation},
journal = {Metallography, Microstructure and Analysis},
year = {2023},
url = {https://link.springer.com/article/10.1007/s13632-023-01020-7},
doi = {10.1007/s13632-023-01020-7}
}
|
| Hariharan V, Nithin B, Ruban Raj L, Makikeni SK, Murty B and Phanikumar G (2023), "Modeling microsegregation during metal additive manufacturing: impact of dendrite tip kinetics and finite solute diffusion", Crystals. |
| Abstract: Rapid solidification during metal additive manufacturing (AM) leads to non-equilibrium microsegregation, which can result in the formation of detrimental phases and cracking. Most of the microsegregation models assume a Scheil-type solidification, where the solidification interface is planar and there exists a local equilibrium at the interface along with either zero or infinite solute diffusion in the respective participating phases—solid and liquid. This assumption leads to errors in prediction. One has to account for finite solute diffusion and the curvature at the dendritic tip for more accurate predictions. In this work, we compare different microsegregation models, that do and do not consider finite diffusion and dendrite tip kinetics, against experiments. We also propose a method to couple dendrite tip kinetics with the diffusion module (DICTRA®) implemented in Thermo-Calc®. The models which accounted for both finite diffusion and dendrite tip kinetics matched well with the experimental data. |
BibTeX:
@article{Hariharan2023,
author = {Hariharan, VS and Nithin, Baler and Ruban Raj, L. and Surendra Kumar Makikeni and Murty, BS and Phanikumar, Gandham},
title = {Modeling microsegregation during metal additive manufacturing: impact of dendrite tip kinetics and finite solute diffusion},
journal = {Crystals},
year = {2023},
url = {https://www.mdpi.com/2073-4352/13/5/842},
doi = {10.3390/cryst13050842}
}
|
| Hussain U, Phanikumar G and Swaminathan N (2023), "Mapping of multiphase field model parameters to physical factors in order to simulate desired phase transformations", Computational Materials Science. Vol. 226, pp. 112227. |
| Abstract: The multiphase field modelling is a powerful tool to understand sufficiently complicated material transformation phenomena. The numerical implementation of this modelling technique faced many challenges and finally Ohno and Matsuura (2009) provided a consistent model which overcame some of the numerical artifacts of its predecessors. However, the Ohno and Matsuura model has not had a robust numerical implementation. This difficulty in implementation is due to the complicated nature of equations that arise from the model. Furthermore, fitting the model for the desired problem needs a thorough understanding of the behaviour of the model parameters. Hence, this work uses an FEM based solver to understand the use of parameters in a multiphase field model and their effect on interface characteristics. Finally, it is shown how the parameters of the model can be tuned to simulate common types of phase transformation. |
BibTeX:
@article{Hussain2023,
author = {Umair Hussain and Gandham Phanikumar and Narasimhan Swaminathan},
title = {Mapping of multiphase field model parameters to physical factors in order to simulate desired phase transformations},
journal = {Computational Materials Science},
year = {2023},
volume = {226},
pages = {112227},
url = {https://www.sciencedirect.com/science/article/pii/S0927025623002215},
doi = {10.1016/j.commatsci.2023.112227}
}
|
| Jain R, Rahul M, Chakraborty P, Sabat RK, Samal S, Park N, Phanikumar G and Tewari R (2023), "Integrated experimental and modeling approach for hot deformation behavior of Co-Cr-Fe-Ni-V high entropy alloy", Journal of Materials Research and Technology. Vol. 25, pp. 840-854. |
| Abstract: The study aims to investigate the hot deformation behavior of Co–Cr–Fe–Ni–V high entropy alloy (HEA) at temperatures ranging from 1073 K to 1373 K and strain rates of 0.001, 0.01, 1, and 10 s−1, and to generate processing maps using dynamic materials modeling (DMM) to identify the optimum processing domain for industrial applications. The material's hardening and softening characteristics are also explored under various hot working conditions. Deformation twinning is observed in materials deformed at 0.1 s−1 at 1273 K and 1373 K, contributing to their observed hardening. The mean free path of dislocation defines the material's strength, and the transition point from dynamic recovery to dislocation-dislocation or dislocation-solute interaction occurs when the mean free path of dislocation reaches its lowest value. The inhomogeneity in the deformed sample is correlated with the strain field distribution using an integrated approach using finite element method (FEM) modeling and electron backscattered diffraction (EBSD) results. EBSD characterization reveals the presence of deformation bands and annealing twins at low and high temperatures, respectively. Additionally, an artificial neural network (ANN) model is proposed to predict the hot deformation behavior of Co–Cr–Fe–Ni–V HEA, with promising results, as evidenced by a correlation coefficient (R) of 0.9983 and an average absolute relative error (AARE) of 2.71% on the test dataset. |
BibTeX:
@article{Jain2023,
author = {Reliance Jain and Rahul, MR and Poulami Chakraborty and Rama Krushna Sabat and Sumanta Samal and Nokeun Park and Gandham Phanikumar and Raghvendra Tewari},
title = {Integrated experimental and modeling approach for hot deformation behavior of Co-Cr-Fe-Ni-V high entropy alloy},
journal = {Journal of Materials Research and Technology},
year = {2023},
volume = {25},
pages = {840--854},
url = {https://www.sciencedirect.com/science/article/pii/S2238785423012231},
doi = {10.1016/j.jmrt.2023.05.257}
}
|
| John DM and Phanikumar G (2023), "New Horizons in Metallurgy, Materials and Manufacturing" Singapore , pp. 51-68. Springer. |
BibTeX:
@inbook{John2023,
author = {Deepu Mathew John and Gandham Phanikumar},
editor = {Shrivastava, A. and Arora, A. and Srivastava, C. and Dhawan, N. and Shekhar Singh, S.},
title = {New Horizons in Metallurgy, Materials and Manufacturing},
publisher = {Springer},
year = {2023},
pages = {51--68},
url = {https://link.springer.com/chapter/10.1007/978-981-19-5570-9_4},
doi = {10.1007/978-981-19-5570-9_4}
}
|
| Kumar P, Jain R, Rahul M, Ghosh A, Samal S and Phanikumar G (2023), "High Temperature Deformation Behavior and Processing Maps of FeCoNiCrAlTi Dual Phase High Entropy Alloy", Metals and Materials International. Vol. 29 |
| Abstract: The present study explores the high temperature deformation behavior of FeCoNiCrAlTi dual phase high entropy alloy (henceforth referred to as DP-HEA) in the temperature range of 900–1100 °C (1173–1373 K) and the strain rate varying from 0.001 to 0.1 s^−1. The as-cast sample has been characterized using scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry, which reveals the presence of two phases, disordered γ and ordered γ′. A constitutive relationship between the process parameters (stress temperature, strain, and strain rate) has been drawn using the Arrhenius-type equation to recognize the high temperature deformation behavior of the DP-HEA. The optimum thermomechanical processing window of the DP-HEA has been determined by constructing multiple contour maps based on different parameters such as efficiency, strain rate sensitivity, etc. And the optimum processing domain has been found to lie approximately in the temperature range of 1260–1300 K and SR = 10^–2.3–10^–2 s^−1, 1325–1373 K and SR = 10^–1.4–10^–1 s^−1 & 1173–1193 K and SR = 10^–1.3–10^–1.55 s^−1. Finally, the stable and unstable regimes in the processing maps are correlated with the microstructure of hot deformed samples. |
BibTeX:
@article{Kumar2023,
author = {Piyush Kumar and Reliance Jain and MR Rahul and Abhijit Ghosh and Sumanta Samal and Gandham Phanikumar},
title = {High Temperature Deformation Behavior and Processing Maps of FeCoNiCrAlTi Dual Phase High Entropy Alloy},
journal = {Metals and Materials International},
year = {2023},
volume = {29},
doi = {10.1007/s12540-023-01399-6}
}
|
| Kumar P, Rahul M, Samal S, Ghosh A and Phanikumar G (2023), "Constitutive Behavior With Microstructure and Texture Evolution During the High-Temperature Deformation of Fe11.5Co20.6Ni40.7Cr12.2Al7.8Ti7.2 High-Entropy Alloy", Metallurgical and Materials Transactions A. Vol. 54, pp. 3249-3260. |
| Abstract: Microstructure and texture evolution of the Fe11.5Co20.6Ni40.7Cr12.2Al7.8Ti7.2 (at. pct) high-entropy alloy during the high-temperature deformation has been investigated in the temperature range of 1173 K to 1373 K and strain rate of 0.1 to 0.001 s−1. The stress–strain curve obtained from the deformation indicates significant flow softening at low temperatures. The softening at 1173 K is due to cracking, whereas high-temperature softening is attributed to dynamic recrystallization (DRX). Arrhenius-type sine hyperbolic relationship is used to carry out the flow stress analysis, and the predicted flow stress shows good agreement with the experimental results with an accuracy of (R2 = 0.955), especially when the deformation takes place at a low strain rate. The estimated strain hardening exponent, n (> 3), and activation energy, Q (> 400 kJ/mol), indicated that the deformation mechanism is dislocation controlled. Detailed microstructural and textural characterization of the hot deformed sample has been carried out using EBSD analysis. Microstructural investigation confirms that dynamic recrystallization is the primary reason behind the flow softening for the samples deformed at 1273 K and above. Strain-free recrystallized grains are found to nucleate near the grain boundary region. Furthermore, the size of the recrystallized grains increases with an increase in temperature and a decrease in strain rate. The volume fraction of the recrystallized grains is found to decrease with an increase in the Zener Holloman parameter. DRX grain was found to possess a weak texture with a low texture index. |
BibTeX:
@article{Kumar2023a,
author = {Piyush Kumar and Rahul, MR and Sumanta Samal and Abhijit Ghosh and Gandham Phanikumar},
title = {Constitutive Behavior With Microstructure and Texture Evolution During the High-Temperature Deformation of Fe11.5Co20.6Ni40.7Cr12.2Al7.8Ti7.2 High-Entropy Alloy},
journal = {Metallurgical and Materials Transactions A},
year = {2023},
volume = {54},
pages = {3249--3260},
url = {https://link.springer.com/article/10.1007/s11661-023-07093-x},
doi = {10.1007/s11661-023-07093-x}
}
|
| Kumar S, Pradhan H, Shah N, Rahul MR and Phanikumar G (2023), "Machine learning enabled processing map generation for high-entropy alloy", Scripta Materialia. Vol. 234 |
| Abstract: Identifying optimum processing conditions is necessary for new material development. The flow curves can be used to develop the processing map for an alloy. The current study trained multiple machine learning models such as Random Forest Regressor (RFR), K Nearest Neighbors (KNN), Extra Tree Regressor (ETR) and Artificial Neural Network (ANN) to predict the flow behaviour of the material. The testing R2 fit score of more than 0.99 was obtained for all four algorithms, and trained models were used to generate the flow curves at various temperature strain rate combinations for CoCrFeNiTa0.395 eutectic high entropy alloy. A processing map was developed using the results from ANN and validated with the experimental microstructure observations. |
BibTeX:
@article{Kumar2023b,
author = {Saphal Kumar and Hrutidipan Pradhan and Naishalkumar Shah and Rahul MR and Gandham Phanikumar},
title = {Machine learning enabled processing map generation for high-entropy alloy},
journal = {Scripta Materialia},
year = {2023},
volume = {234},
url = {https://www.sciencedirect.com/science/article/pii/S1359646223002671},
doi = {10.1016/j.scriptamat.2023.115543}
}
|
| Kushwaha S, Agilan M, Rahul MR and Phanikumar G (2023), "Study of TIG weld microstructure formation in Inconel 718 alloy using ICME approach", Integrating Materials and Manufacturing Innovation. |
| Abstract: The detrimental phase formation in Inconel 718 weld microstructure depends on welding conditions. This study uses the FEM simulation of the welding process to establish the variation of temperature gradient and cooling rate in the weld pool boundary as a function of welding current and speed. The microstructure evolution in the weld pool was established using phase field simulation as a function of temperature gradient and cooling rate variation. Thermal simulations ensured experimental validation of the macro and micro-scale simulations. The elemental segregation in the interdendritic region is analyzed, and a phase map was proposed to identify the safe domain for the welding process. The micro-segregation maps guide the selection of optimum welding process parameters. The current study develops and verifies an ICME framework for welding process optimization. |
BibTeX:
@article{Kushwaha2023,
author = {Shambhu Kushwaha and Agilan, M and Rahul, M. R. and Gandham Phanikumar},
title = {Study of TIG weld microstructure formation in Inconel 718 alloy using ICME approach},
journal = {Integrating Materials and Manufacturing Innovation},
year = {2023},
url = {https://link.springer.com/article/10.1007/s40192-023-00317-3},
doi = {10.1007/s40192-023-00317-3}
}
|
| Mangalarapu TB, Kumar S, Gandham P and Koppoju S (2023), "Cold spraying of Al-aerospace alloys: ease of coating deposition at high stagnation temperatures", Surface & Coatings Technology. Vol. 467, pp. 129703. |
| Abstract: Cold spray is the only solid-state coating technique to deposit thick metallic coatings. Deposition of metallic and metallic alloy powders is carried out at the temperature lower than the melting point. Since spraying of Al-based aerospace alloys are associated with nozzle clogging, successful deposition is restricted to nitrogen or helium as the main process gas with a polymer nozzle. Deposition of the alloys using air as process gas at elevated stagnation temperatures (up to 600 °C) has benefits in the repair and refurbishment sector, especially in aerospace. In this study, the effect of elevated stagnation temperatures (from 400 to 600 °C) using air as the main process gas on the deposition characteristics of aerospace grade Al-alloys (Cp-Al, Al-2024, Al-6061 and Al-7075) is studied. Deposition of the alloys at various stagnation temperatures is studied using FEM and correlated with the coating thickness. The deposition behaviour is studied using various parameters such as lattice misfit calculations and solid solution strengthening calculations. The ease of cold spray deposition of Al-aerospace alloys is systematically studied and listed as Al-6061 > Cp-Al > Al-7075 > Al-2024 for the first time. |
BibTeX:
@article{Mangalarapu2023,
author = {Tarun Babu Mangalarapu and S. Kumar and Phanikumar Gandham and Suresh Koppoju},
title = {Cold spraying of Al-aerospace alloys: ease of coating deposition at high stagnation temperatures},
journal = {Surface & Coatings Technology},
year = {2023},
volume = {467},
pages = {129703},
url = {https://www.sciencedirect.com/science/article/pii/S0257897223004784},
doi = {10.1016/j.surfcoat.2023.129703}
}
|
| Zhong C, Narayana Samy VP, Pirch N, Gasser A, Phanikumar G and Schleifenbaum JH (2023), "Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates: Modeling, Simulation, and Experiments", 3D Printing and Additive Manufacturing. |
| Abstract: Laser metal deposited processed Ni-based superalloy IN718 is characterized by elemental micro-segregation, anisotropy, and Laves phases due to the rapid solidification and therefore needs homogenization heat treatment to achieve comparable properties of wrought alloys. In this article, we report a simulation-based methodology to design heat treatment IN718 in a laser metal deposition (LMD) process by using Thermo-calc. Initially, the finite element modeling simulates the laser melt pool to compute the solidification rate (G) and temperature gradient (R). Then, the primary dendrite arm spacing (PDAS) is computed through Kurz-Fisher and Trivedi modeling integrated with finite element method (FEM) solver. Later, a DICTRA homogenization model based on the PDAS input values computes the homogenization heat treatment time and temperature. The simulated time scales are verified for two different experiments with contrast laser parameters and are found to be in good agreement confirmed with the results from scanning electron microscopy. Finally, a methodology for integrating the process parameter with the heat treatment design is developed, and a heat treatment map for IN718 is generated that can be integrated with an FEM solver for the first time in the LMD process. |
BibTeX:
@article{Zhong2023,
author = {Zhong, C and Narayana Samy, V P and Pirch, N and Gasser, A and Phanikumar, G and Johannes Henrich Schleifenbaum},
title = {Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates: Modeling, Simulation, and Experiments},
journal = {3D Printing and Additive Manufacturing},
year = {2023},
url = {https://doi.org/10.1089/3dp.2021.0115}
}
|
| Agilan M, Phanikumar G and Sivakumar D (2022), "Tensile behaviour and microstructure evolution in friction stir welded 2195–2219 dissimilar aluminium alloy joints", Welding in the World. Vol. 66(2), pp. 1-11. |
| Abstract: 2XXX series aluminium alloys are widely used in propellant tanks of space launch vehicles. In this work, friction stir welding (FSW) was performed to produce dissimilar joints between 2195 and 2219 alloys. The effect of temperature (ambient, 77K and 20K) on the tensile properties of 2195–2219 joints was investigated. Results showed that a decrease in temperature increased the tensile properties significantly without a reduction in ductility. Due to contribution from 2195 alloy, the properties of the dissimilar joint were marginally higher than the 2219 similar joint. The failure location in the thermo-mechanically affected zone (TMAZ) of the 2219 side was substantiated with the hardness survey across the weld. The effect of material position at advancing side (AS) and retreating side (RS) on tensile properties of dissimilar joints was investigated. Results depicted that regardless of the material position, the failure was consistently observed at TMAZ of 2219. However, placing 2219 at the AS showed better properties than at RS. This study brought out the tensile behaviour at cryogenic temperatures and suitable material position to achieve optimum strength, which are key inputs for designing launch vehicle structures. |
BibTeX:
@article{Agilan2022,
author = {Agilan, M. and Phanikumar, G. and Sivakumar, D.},
title = {Tensile behaviour and microstructure evolution in friction stir welded 2195–2219 dissimilar aluminium alloy joints},
journal = {Welding in the World},
year = {2022},
volume = {66},
number = {2},
pages = {1--11},
url = {https://link.springer.com/article/10.1007/s40194-021-01217-w},
doi = {10.1007/s40194-021-01217-w}
}
|
| Agilan M, Satyamshreshta K, Sivakumar D and Phanikumar G (2022), "High-Throughput Experiment and Numerical Simulation to Study Solidification Cracking in 2195 Aluminum Alloy Welds", Metallurgical and Materials Transactions A. Vol. 53, pp. 1906-1918. |
BibTeX:
@article{Agilan2022a,
author = {Agilan, M and Satyamshreshta, K and Sivakumar, D and Phanikumar, G},
title = {High-Throughput Experiment and Numerical Simulation to Study Solidification Cracking in 2195 Aluminum Alloy Welds},
journal = {Metallurgical and Materials Transactions A},
year = {2022},
volume = {53},
pages = {1906--1918},
url = {https://link.springer.com/article/10.1007/s11661-022-06655-9},
doi = {10.1007/s11661-022-06655-9}
}
|
| Galenko P, Toropova L, Alexandrov D, Phanikumar G, Assadi H, Reinartz M, Paul P, Fang Y and Lippmann S (2022), "Anomalous kinetics, patterns formation in recalescence, and final microstructure of rapidly solidified Al-rich Al-Ni alloys", Acta Materialia. |
| Abstract: From thermodynamical consideration, rather a monotonically increasing crystal growth velocity with increasing undercooling is expected in the crystallization of liquids, mixtures, and alloys [P.K. Galenko and D. Jou, Physics Reports 818 (2019) 1]. By contrast to this general theoretical statement, Al-rich Al-Ni alloys show an anomalous solidification behavior: the solid-liquid interface velocity slows down as the undercooling increases [R. Lengsdorf, D. Holland-Moritz, D. M. Herlach, Scripta Materialia 62 (2010) 365]. It is also found that besides the anomalous growth behaviour, changes in the shape of the recalescence front as the growth front morphology occur. In the light of recent measurements in microgravity with an Al-25at.% Ni alloy sample onboard the International Space Station (ISS) results confirming this anomalous behavior as an unexpected trend in solidification kinetics are presented. The measurements show multiple nucleation events forming the growth front, a mechanism that has been observed for the first time in Al-Ni alloys [D. Herlach et al., Physical Review Materials 3 (2019) 073402; M. Reinartz et al. JOM 74 (2022) 2420] and summarized with detailed analysis in the present publication over a wider range of concentrations. Particularly, the experimental measurements and obtained data directly demonstrate that the growth front does thus not consist of dendrite tips (as in usual rapid solidifying samples), but of newly forming nuclei propagating along the sample surface in a coordinated manner. Theoretical analysis on intensive nucleation ahead of crystal growth front is made using the previously developed model [D.V. Alexandrov, Journal of Physics A: Mathematical and Theoretical 50 (2017) 345101]. Using equations of this model, quantitative calculations confirm the interpretation of experimentally observed propagation of the recalescence front and obtained data on the microstructure of droplets solidified in electromagnetic levitation facility (EML) on the Ground, under reduced gravity during parabolic flights, and in microgravity conditions onboard the ISS. |
BibTeX:
@article{Galenko2022,
author = {Galenko, P.K. and Toropova, L.V. and Alexandrov, D.V. and Phanikumar, G. and Assadi, H and Reinartz, M. and Paul, P and Fang, Y. and Lippmann, S.},
title = {Anomalous kinetics, patterns formation in recalescence, and final microstructure of rapidly solidified Al-rich Al-Ni alloys},
journal = {Acta Materialia},
year = {2022},
url = {https://www.sciencedirect.com/science/article/pii/S1359645422007625},
doi = {10.1016/j.actamat.2022.118384}
}
|
| Goud VS, Rahul MR and Phanikumar G (2022), "Prediction of growth velocity of undercooled multicomponent metallic alloys using a machine learning approach", Scripta Materialia. Vol. 207, pp. 114309. |
| Abstract: Establishing growth kinetics of undercooled metallic alloys is essential to understand microstructure evolution during solidification processing. The complexity of the physical processes have hitherto limited growth models to simple assumptions that do not lead to satisfactory predictive capability. Experimental measurements of growth velocity as a function of undercooling are also tedious. The current study uses experimental and literature data to train the machine learning algorithms. Five algorithms are trained: Random Forest, Bagging Regressor, Gradient Boosting Regressor, XGBoost, and Artificial Neural Network. A labeled data set of 910 was used, with 70% data for training and 30 % data for testing. An R2 cross-validation score of more than 0.89 was obtained for ANN. The trained algorithms are used to predict the growth velocity of medium and high entropy alloys show good compatibility with the experimental data. |
BibTeX:
@article{Goud2022,
author = {Vanga Sreekar Goud and Rahul, M. R. and Gandham Phanikumar},
title = {Prediction of growth velocity of undercooled multicomponent metallic alloys using a machine learning approach},
journal = {Scripta Materialia},
year = {2022},
volume = {207},
pages = {114309},
url = {https://www.sciencedirect.com/science/article/pii/S1359646221005893},
doi = {10.1016/j.scriptamat.2021.114309}
}
|
| Hariharan V, Pramod S, Kesavan D, Murty B and Phanikumar G (2022), "ICME framework to simulate microstructure evolution during laser powder bed fusion of Haynes 282 nickel-based superalloy", Journal of Materials Science. |
| Abstract: Haynes 282 is a creep-resistant, γ′ strengthened nickel-based superalloy with excellent weldability. Additive manufacturing, especially laser powder bed fusion (LPBF), of Haynes 282 is being researched for its potential applications in aerospace and power generation sectors. LPBF enables us to achieve desired properties via microstructure control through process parameter optimization. Integrated computational materials engineering (ICME) approach can be used to tune the process parameters to obtain desired microstructure, instead of trial-and-error methods. In this report, ICME framework has been established to simulate microstructural evolution during LPBF and post-processing of Haynes 282. A dimensionless number was used to optimize the process parameters with minimal porosity. Thermal modelling was performed using a semi-analytical model and the obtained thermal data was used to simulate solidification during LPBF. The corresponding cell spacing obtained matched closely with the experimental data. The segregation pattern extracted from the phase-field model was used as input for homogenization simulation. The γ′ precipitate evolution was predicted using Langer–Schwartz theory and Kampmann–Wagner-Numerical (KWN) approach. The predicted values agreed with the experimentally measured values. The room temperature yield strength of as-built samples was comparable and that of heat-treated samples were superior to the aged wrought material. |
BibTeX:
@article{Hariharan2022,
author = {Hariharan, V.S. and Pramod, S. and Kesavan, D. and Murty, B.S. and Phanikumar, Gandham},
title = {ICME framework to simulate microstructure evolution during laser powder bed fusion of Haynes 282 nickel-based superalloy},
journal = {Journal of Materials Science},
year = {2022},
url = {https://link.springer.com/article/10.1007/s10853-022-07170-3},
doi = {10.1007/s10853-022-07170-3}
}
|
| Rahul M R, Agilan M, Mohan D and Phanikumar G (2022), "Integrated experimental and simulation approach to establish the effect of elemental segregation in Inconel 718 welds", Materialia. , pp. 101593. |
| Abstract: Inconel 718 as-welded structures are widely used in many critical applications. Welding will cause different types of detrimental phase formation and segregation of elements in the inter-dendritic region. The segregation of elements depends on the local curvatures during morphological evolution dictated by the thermal conditions prevailing during the process. In this study, we establish the segregation behavior of Inconel 718 as a function of solidification conditions. Microstructure evolution was correlated with Scheil's solidification predictions for different cooling rates and temperature gradients. The solidification pathway of segregated composition depends on the process parameters via the microstructure. Simulation results are validated with the experimental results, and the microstructure comparison shows good agreement. An integrated workflow is proposed to accelerate the welding process optimization and produce desired microstructure for multi-component alloys. |
BibTeX:
@article{RahulM2022,
author = {Rahul M R and Agilan M and Dasari Mohan and Gandham Phanikumar},
title = {Integrated experimental and simulation approach to establish the effect of elemental segregation in Inconel 718 welds},
journal = {Materialia},
year = {2022},
pages = {101593},
url = {https://www.sciencedirect.com/science/article/pii/S2589152922002745},
doi = {10.1016/j.mtla.2022.101593}
}
|
| Shah N, John DM, Rahul M R and Phanikumar G (2022), "Microstructure prediction of eutectic high entropy alloy using physical and computer simulation for additive manufacturing condition", Journal of Alloys and Compounds. , pp. 167268. |
| Abstract: The additive manufacturing (AM) of eutectic high-entropy alloys (EHEAs) with seven components was simulated. The as-cast alloy comprised of primary dendritic phase and eutectic region between the FCC and Laves phase. The additive thermal cycle generated by the analytical model was used for phase-field and physical simulations. A thermomechanical simulator was used to perform the physical simulation. Scanning electron microscopy (SEM) was used to characterize the effect of AM on the thermal cycle of the test samples and the results showed that the sigma phase was formed in the primary dendritic phase. The formation of the sigma phase was correlated with thermodynamic predictions and heat treatment studies. The thermal cycle of the microstructure, which was predicted using the phase-field simulation, was correlated with the experimental results. The integrated approach that was adopted in the current study can be utilized for the accelerated exploration of alloys for additive manufacturing. |
BibTeX:
@article{Shah2022,
author = {Naishalkumar Shah and Deepu Mathew John and Rahul M R and Gandham Phanikumar},
title = {Microstructure prediction of eutectic high entropy alloy using physical and computer simulation for additive manufacturing condition},
journal = {Journal of Alloys and Compounds},
year = {2022},
pages = {167268},
url = {https://www.sciencedirect.com/science/article/pii/S0925838822036593},
doi = {10.1016/j.jallcom.2022.167268}
}
|
| Singh UP, Swaminathan S and Phanikumar G (2022), "Thermo-mechanical approach to study the residual stress evolution in part-scale component during laser additive manufacturing of alloy 718", Materials & Design. Vol. 222, pp. 111048. |
| Abstract: Laser Additive Manufacturing (LAM) is a promising technology for manufacturing gas turbine compo- nents with enhanced design capability and a significant reduction in part weight. Additive manufacturing of alloy 718 using Laser Powder Bed fusion (L-PBF) process poses certain challenges pertaining to com- plex residual stress, micro-segregation of Nb, and undesired Laves phase formation in the as-printed state. The built-up residual stress and undesired brittle phase may lead to cracks and build failures. This article studied residual stress evolution during L-PBF of alloy 718 using Finite Element (FE) thermo-mechanical simulation implemented in Simufact AdditiveÒ software. The model adopted the bundling of physical powder in voxel mesh to minimize the computational time and mimic the actual process scenario during part-scale simulation. Experimental flow curves generated from Gleeble 3800Ò tests at elevated temperatures were utilized to calibrate material property for better accuracy in the FE simulation. The calibrated model was used to study the residual stress evolution during support struc- ture removal. Verification and validation of simulated results were performed using X-ray diffraction (XRD) measurements. The simulated value agrees well with the experimental value with a maximum deviation of 7%. Finally, the experimentally validated model was used to correlate the effect of layer thickness variation on residual stress evolution. |
BibTeX:
@article{Singh2022,
author = {Uday Pratap Singh and Srinivasan Swaminathan and Gandham Phanikumar},
title = {Thermo-mechanical approach to study the residual stress evolution in part-scale component during laser additive manufacturing of alloy 718},
journal = {Materials & Design},
year = {2022},
volume = {222},
pages = {111048},
url = {https://www.sciencedirect.com/science/article/pii/S0264127522006700},
doi = {10.1016/j.matdes.2022.111048}
}
|
| Tarun Babu M, Kumar S, Ramakrishna M, Phanikumar G and Suresh K (2022), "Precipitation behavior of cold sprayed Al6061 coatings", Materialia. Vol. 24, pp. 101510. |
| Abstract: Cold spray coating technique is an established technology where deposition of the desired coating is carried out at temperatures below the melting point. Current literature on the application of cold spray technique, particularly using Al-6061 alloy powder was reviewed. In this work, we report the precipitation behavior of the cold sprayed Al6061 coatings in the directly aged (as-deposited and aged) and solutionized aged conditions. Coatings were deposited using a convergent-divergent (De-Laval) nozzle at a pressure of 20 bar and a temperature of 400 °C using air as a carrier gas. The peak hardness of the directly aged coatings (107±3 HV0.3) is similar to the bulk counterpart (110±2 HV0.3 ). The peak hardness of the directly aged coating is attributed to mixture of highly strained microstructure, fine and coarse grains. Needle-shaped 𝛽” (Mg5Si6) precipitates contribute to peak hard- ness of solutionized aged coatings. The directly aged coatings have not exhibited 𝛽” (Mg5 Si6) precipitates because of segregation of solute at the cell boundaries, Al-Mg-Fe, and Mg-Si rich particles. There is an improvement in bonding for directly aged coatings, and significant improvement in bonding with solutionized aged coatings. |
BibTeX:
@article{TarunBabu2022,
author = {Tarun Babu, Mangalarapu and Kumar, S and Ramakrishna, M and Gandham Phanikumar and Suresh, K},
title = {Precipitation behavior of cold sprayed Al6061 coatings},
journal = {Materialia},
year = {2022},
volume = {24},
pages = {101510},
url = {https://www.sciencedirect.com/science/article/pii/S2589152922001934},
doi = {10.1016/j.mtla.2022.101510}
}
|
| Jain R, Rahul MR, Chakraborty P, Sabat RK, Samal S, Phanikumar G, Raghvendra and Tewari (2021), "Design and deformation characteristics of single-phase Co-Cr-Fe-Ni-V high entropy alloy", Journal of Alloys and Compounds. Vol. 888(161579), pp. 161579. |
| Abstract: In the present study, using ICME approach, the development of Co-Cr-Fe-Ni-V based single-phase FCC high entropy alloy (HEA) has been explored. The simulation guided composition was arc melted and verified using microstructure characterization. The as-cast sample was subjected to deformation at a strain rate of 0.1 s−1in the temperature range of 1073–1373 K. The flow stress behavior in this temperature range could be correlated with the evolution of microstructure using EBSD. Based on these results, the deformation behavior of the alloy at elevated temperature is rationalized. The current study realizes the ICME approach to develop novel single-phase FCC HEA. |
BibTeX:
@article{Jain2021,
author = {Reliance Jain and M. R. Rahul and Poulami Chakraborty and Rama Krushna Sabat and Sumanta Samal and Gandham Phanikumar and Raghvendra and Tewari},
title = {Design and deformation characteristics of single-phase Co-Cr-Fe-Ni-V high entropy alloy},
journal = {Journal of Alloys and Compounds},
year = {2021},
volume = {888},
number = {161579},
pages = {161579},
url = {https://www.sciencedirect.com/science/article/pii/S0925838821029881},
doi = {10.1016/j.jallcom.2021.161579}
}
|
| Jaiswal U, Krishna YV, Rahul MR and Phanikumar G (2021), "Machine learning-enabled identification of new medium to high entropy alloys with solid solution phases", Computational Materials Science. Vol. 197, pp. 110623. |
| Abstract: Identification of compositions that form solid solution phases from a large compositional space is challenging. The current study focuses on applying multiple machine learning classification algorithms for suitably predicting new medium to high entropy alloys with solid solution phases. The current data set used for training and testing consisting of 664 labeled data with 267 BCC alloys, 199 FCC alloys, and 198 (FCC + BCC) alloys to avoid biased predicting. The analyzed data shows a strong correlation between the empirical design parameters. The correlation coefficient values changed while moving the alloy system from medium to high entropy domain. The parameters VEC and Tm show high importance in prediction compared to other parameters. The importance of design parameters is analyzed, and the accuracy is quantified. The experimental results validate the prediction of a shift from BCC + FCC to FCC phases while increasing Ni content in the CoCuFeNix system. |
BibTeX:
@article{Jaiswal2021,
author = {Jaiswal, UK and Krishna, Y V and Rahul, M R and Phanikumar, G},
title = {Machine learning-enabled identification of new medium to high entropy alloys with solid solution phases},
journal = {Computational Materials Science},
year = {2021},
volume = {197},
pages = {110623},
url = {https://www.sciencedirect.com/science/article/pii/S0927025621003505},
doi = {10.1016/j.commatsci.2021.110623}
}
|
| Priya GK, Deepu MJ, Venkatesh P and Phanikumar G (2021), "Integrated Computational Materials Engineering-based simulation of detrimental precipitates in power plant steel weld", Journal of Materials Engineering and Performance. , pp. 1-8. |
BibTeX:
@article{Priya2021,
author = {Priya, G K and Deepu, M J and Venkatesh, P and Phanikumar, G},
title = {Integrated Computational Materials Engineering-based simulation of detrimental precipitates in power plant steel weld},
journal = {Journal of Materials Engineering and Performance},
year = {2021},
pages = {1--8},
url = {https://rdcu.be/cfJOW},
doi = {10.1007/s11665-021-05502-z}
}
|
| Shah N, Rahul M and Phanikumar G (2021), "Accelerated design of eutectic high entropy alloys by ICME approach", Metallurgical and Materials Transactions A. Vol. 52, pp. 1574-1580. |
| Abstract: Eutectic high entropy alloy with seven components is designed based on the integrated computational materials engineering (ICME) framework. The framework includes thermodynamic prediction using calculation of phase diagrams (CALPHAD), microstructure simulation using phase-field method, and experimental validation. The designed alloy shows the eutectic structure consisting of FCC and laves phase in the composition range from 8.25 to 10 at. pct Ta. The simulation and experimental results are co-related and a framework is proposed that can be used for high entropy alloy design subjected to various manufacturing processes. |
BibTeX:
@article{Shah2021,
author = {Naishalkumar Shah and Rahul, M.R. and Gandham Phanikumar},
title = {Accelerated design of eutectic high entropy alloys by ICME approach},
journal = {Metallurgical and Materials Transactions A},
year = {2021},
volume = {52},
pages = {1574--1580},
url = {https://link.springer.com/article/10.1007%2Fs11661-021-06218-4},
doi = {10.1007/s11661-021-06218-4}
}
|
| Shah N, Rahul M, Bysakh S and Phanikumar G (2021), "Microstructure stability during high temperature deformation of CoCrFeNiTa eutectic high entropy alloy through nano-scale precipitation", Materials Science and Engineering: A. Vol. 824(141793) |
BibTeX:
@article{Shah2021a,
author = {Naishalkumar Shah and M.R. Rahul and Sandip Bysakh and Gandham Phanikumar},
title = {Microstructure stability during high temperature deformation of CoCrFeNiTa eutectic high entropy alloy through nano-scale precipitation},
journal = {Materials Science and Engineering: A},
year = {2021},
volume = {824},
number = {141793},
url = {https://www.sciencedirect.com/science/article/pii/S0921509321010595},
doi = {10.1016/j.msea.2021.141793}
}
|
| Sivaji K and Phanikumar G (2021), "Microstructure and Precipitation Studies of Gas Tungsten Arc Welded Haynes 282 Superalloy", Materials Science Forum., 01, 2021. Vol. 1016, pp. 666-671. |
BibTeX:
@article{Sivaji2021,
author = {Karna Sivaji and Gandham Phanikumar},
title = {Microstructure and Precipitation Studies of Gas Tungsten Arc Welded Haynes 282 Superalloy},
journal = {Materials Science Forum},
year = {2021},
volume = {1016},
pages = {666--671},
url = {https://www.scientific.net/MSF.1016.666},
doi = {10.4028/www.scientific.net/MSF.1026.666}
}
|
| Baler N, Pandey P, Palanisamy D, Makineni SK, Phanikumar G and Chattopadhyay K (2020), "On the effect of W addition on microstructural evolution and gamma-prime precipitate coarsening in a Co-30Ni-10Al-5Mo-2Ta-2Ti alloy", Materialia. Vol. 10, pp. 100632. |
| Abstract: The effect of replacement of molybdenum with small amount of tungsten on the stability of cobalt based superalloys of Co–Ni–Mo–Al–Ta–Ti class has been presented. A small addition of tungsten (W) in Co–30Ni–(5-x)Mo–10Al–2Ta–2Ti–2W alloys stabilizes the cuboidal morphology of precipitates and increases the γ′ volume fraction. A 2 at% addition of W causes an increase of 60 °C in solvus temperature of the base superalloy to reach a value of 1130 °C with a slight increase of mass density to 8.79 g/cc. Beside partitioning into γ′, W also shifts the partitioning preference of Mo from the γ′ phase in 0W alloy to that of equal partitioning in both γ and γ’ phases in 2W alloy. An interfacial confinement of Mo atoms could be observed at the γ/γ′ interfaces that reduces interface energy leading to enhanced microstructural stability. The experimentally determined temporal evolution of average precipitate size in the 2W alloy at the temperatures of 800, 900 and 950 °C suggests a matrix diffusion limited coarsening kinetics. The estimated coarsening rate constant at 900 °C follows a quasi-steady state model and is comparable to those observed for W and Re containing Co-based superalloys. The activation energy for γ′ precipitate coarsening is estimated to be 258 ± 6 kJ/mole, which is comparable to the Mo diffusion in the γ-Co matrix suggesting Mo diffusion still controls the precipitate coarsening in the 2W alloy. |
BibTeX:
@article{Baler2020,
author = {Nithin Baler and Prafull Pandey and Dhanalakshmi Palanisamy and Surendra Kumar Makineni and Gandham Phanikumar and Kamanio Chattopadhyay},
title = {On the effect of W addition on microstructural evolution and gamma-prime precipitate coarsening in a Co-30Ni-10Al-5Mo-2Ta-2Ti alloy},
journal = {Materialia},
year = {2020},
volume = {10},
pages = {100632},
url = {https://www.sciencedirect.com/science/article/pii/S2589152920300491},
doi = {10.1016/j.mtla.2020.100632}
}
|
| Jain R, Rahul M, Samal S, Kumar V and Phanikumar G (2020), "Hot workability of Co-Fe-Mn-Ni-Ti eutectic high entropy alloy", Journal of Alloys and Compounds. Vol. 822, pp. 153609. |
| Abstract: Multicomponent Co25Fe25Mn5Ni25Ti20 eutectic high entropy alloy (EHEA), synthesized by vacuum arc melting followed by suction casting method resulted in two types of solid solution phases (fcc CoFeNi-rich (α) and bcc Ti-rich (β)) and Ti2(Ni, Co) type Laves phase. The hot deformation behaviours have been investigated at a temperature ranging from 1073 to 1273 K and different strain rates (10−3,10−2,10−1and 1 s−1). The optimum hot workability conditions of EHEA lies in temperature range 1073–1273 K and strain rate range 10−3 s−1-10−1.6 s−1 as well as temperature 1130–1225K and strain rate 10−0.5-1 s−1. The constitutive relation is established to understand the plastic deformability at high temperature. Finite element simulation has also been used to predict the deformation behaviour during the hot working process. |
BibTeX:
@article{Jain2020,
author = {Reliance Jain and M.R. Rahul and Sumanta Samal and Vinod Kumar and Gandham Phanikumar},
title = {Hot workability of Co-Fe-Mn-Ni-Ti eutectic high entropy alloy},
journal = {Journal of Alloys and Compounds},
year = {2020},
volume = {822},
pages = {153609},
url = {https://www.sciencedirect.com/science/article/pii/S0925838819348558},
doi = {10.1016/j.jallcom.2019.153609}
}
|
| Jain R, Jain A, Rahul MR, Kumar A, Dubey M, Sabat RK, Samal S and Phanikumar G (2020), "Development of ultrahigh strength novel Co-Cr-Fe-Ni-Zr quasi-peritectic high entropy alloy by an integrated approach using experiment and simulation", Materialia. Vol. 14(100896) |
BibTeX:
@article{Jain2020a,
author = {Reliance Jain and Avi Jain and M R Rahul and Ashok Kumar and Mrigendra Dubey and Rama Krushna Sabat and Sumanta Samal and Gandham Phanikumar},
title = {Development of ultrahigh strength novel Co-Cr-Fe-Ni-Zr quasi-peritectic high entropy alloy by an integrated approach using experiment and simulation},
journal = {Materialia},
year = {2020},
volume = {14},
number = {100896},
url = {https://www.sciencedirect.com/science/article/pii/S2589152920303124},
doi = {10.1016/j.mtla.2020.100896}
}
|
| John DM and Phanikumar G (2020), "ICME Framework for Simulation of Microstructure and Property Evolution During Gas Metal Arc Welding in DP980 Steel", Integrating Materials and Manufacturing Innovation. |
| Abstract: An integrated computational materials engineering (ICME)-based workflow was adopted for the study of microstructure and property evolution at the heat-affected zone (HAZ) of gas metal arc-welded DP980 steel. The macroscale simulation of the welding process was performed with finite element method (FEM) implemented in Simufact Welding® software and was experimentally validated. The time–temperature profile at HAZ obtained from FEM simulation was physically simulated using Gleeble 3800® thermo-mechanical simulator with a dilatometer attachment. The resulting phase transformations and microstructure were studied experimentally. The austenite-to-ferrite and austenite-to-bainite transformations during cooling at HAZ were simulated using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation implemented in JMatPro® software and with phase-field modeling implemented in Micress® software. The phase fractions and the phase transformation kinetics simulated by phase-field method agreed well with experiments. A single scaling factor introduced in JMatPro® software minimized the deviation between calculations and experiments. Asymptotic homogenization implemented in Homat® software was used to calculate the effective macroscale thermo-elastic properties from the phase-field simulated microstructure. FEM-based virtual uniaxial tensile test with Abaqus® software was used to calculate the effective macroscale flow curves from the phase-field simulated microstructure. The flow curve from virtual test simulation showed good agreement with the flow curve obtained with tensile test in Gleeble®. An ICME-based vertical integration workflow in two stages is proposed. With this ICME workflow, effective properties at the macroscale could be obtained by taking microstructure morphology and orientation into consideration. |
BibTeX:
@article{John2020,
author = {Deepu Mathew John and Gandham Phanikumar},
title = {ICME Framework for Simulation of Microstructure and Property Evolution During Gas Metal Arc Welding in DP980 Steel},
journal = {Integrating Materials and Manufacturing Innovation},
year = {2020},
url = {https://link.springer.com/article/10.1007/s40192-020-00182-4},
doi = {10.1007/s40192-020-00182-4}
}
|
| Kurian J, Rahul M, Chelvane JA, Morozkin A, Nigam A, Phanikumar G and Nirmala R (2020), "Enhanced magnetocaloric effect in undercooled rare earch intermetallic compounds RNi (R=Gd, Ho, Er)", Journal of Magnetism and Magnetic Properties. Vol. 499, pp. 166302. |
| Abstract: Equiatomic RNi (where R = Gd, Ho and Er) compounds have been prepared by undercooling. Magnetization data confirm ferromagnetic ordering of the samples at 69 K, 35 K and 10 K (TC) respectively. Magnetocaloric effect (MCE) has been estimated in terms of isothermal magnetic entropy change (ΔSm) near TC. The maximum ΔSm value (ΔSmmax) for 50 kOe field change is about −18 Jkg-1K−1, −20 Jkg-1K−1 and −30 Jkg-1K−1 respectively near TC for the undercooled RNi (R = Gd, Ho and Er) compounds. The ΔSmmax value is more than that obtained for the same compounds prepared by arc-melting and melt-spinning techniques. The observed enhancement in MCE of the undercooled samples could be due to the improved purity that results in faster change of magnetization around the magnetic transition. Thus undercooling rare earth intermetallics and alloys seems to be an attractive, alternative method to synthesize magnetocaloric materials. |
BibTeX:
@article{Kurian2020,
author = {Jinu Kurian and M.R. Rahul and J. Arout Chelvane and A.V. Morozkin and A.K. Nigam and Gandham Phanikumar and R. Nirmala},
title = {Enhanced magnetocaloric effect in undercooled rare earch intermetallic compounds RNi (R=Gd, Ho, Er)},
journal = {Journal of Magnetism and Magnetic Properties},
year = {2020},
volume = {499},
pages = {166302},
url = {https://www.sciencedirect.com/science/article/pii/S0304885319305025},
doi = {10.1016/j.jmmm.2019.166302}
}
|
| Baler N, Pandey P, Chattopadhyay K and Phanikumar G (2020), "Influence of thermomechanical processing parameters on microstructural evolution of a gamm-prime strenghtened cobalt based superalloy during high temperature deformation", Materials Science and Engineering A. Vol. 791, pp. 139498. |
BibTeX:
@article{NithinBaler2020,
author = {Nithin Baler and Prafull Pandey and Kamanio Chattopadhyay and Gandham Phanikumar},
title = {Influence of thermomechanical processing parameters on microstructural evolution of a gamm-prime strenghtened cobalt based superalloy during high temperature deformation},
journal = {Materials Science and Engineering A},
year = {2020},
volume = {791},
pages = {139498},
url = {https://www.sciencedirect.com/science/article/pii/S0921509320305785},
doi = {10.1016/j.msea.2020.139498}
}
|
| Rahul M, Samal S and Phanikumar G (2020), "Metastable microstructures in the solidification of undercooled high entropy alloys", Journal of Alloys and Compounds. Vol. 821, pp. 153488. |
| Abstract: High entropy alloys with multiple phases are taken for undercooling studies and established the microstructure evolution with respect to undercooling. The melt fluxing technique was used for the current study to achieve undercooling. Predictions on the equilibrium phase formation of these systems was performed using CALPHAD approach and compared with experimental observations. Metastable microstructures were observed during undercooling and the morphological changes could be correlated with the currently established mechanisms. The detailed microstructure evolution in FeCoNiCuX0.5 (X = Al, Mo, Ti, W, Zr) shows the minute addition of these elements results in variation in microstructure evolution during as cast as well as undercooled condition. The studied systems show a maximum undercooling of more than 0.18 TL. and maintained crystalline nature even in deep undercooling. The segregation nature of elements was studied and correlated with the phase field simulations obtained. |
BibTeX:
@article{Rahul2020,
author = {M.R. Rahul and Sumanta Samal and Gandham Phanikumar},
title = {Metastable microstructures in the solidification of undercooled high entropy alloys},
journal = {Journal of Alloys and Compounds},
year = {2020},
volume = {821},
pages = {153488},
url = {https://www.sciencedirect.com/science/article/pii/S0925838819347346},
doi = {10.1016/j.jallcom.2019.153488}
}
|
| Rahul M, Samal S, Marshal A, Balaji VN, Pradeep K and Phanikumar G (2020), "Nano-sized Cu clusters in deeply undercooled CoCuFeNiTa high entropy alloy", Scripta Materialia. Vol. 177, pp. 58-64. |
| Abstract: The non-equilibrium response of a high entropy alloy CoCuFeNiTa0.5 has been studied using undercooling as a control parameter. The solidification growth rates are rapid (30–50 m/s) at deep undercooling (>150 °C) and are comparable with conventional alloys. The elemental segregation especially that of Cu as predicted by phase field simulations in lower (<50 °C) undercooling regime matches with the experimental observations. This study indicates that even extreme non-equilibrium conditions during solidification could not avoid elemental segregation at the atomic scale. |
BibTeX:
@article{Rahul2020a,
author = {M.R. Rahul and Sumanta Samal and A. Marshal and V.I. Nithin Balaji and K.G. Pradeep and Gandham Phanikumar},
title = {Nano-sized Cu clusters in deeply undercooled CoCuFeNiTa high entropy alloy},
journal = {Scripta Materialia},
year = {2020},
volume = {177},
pages = {58--64},
url = {https://www.sciencedirect.com/science/article/pii/S1359646219305895},
doi = {10.1016/j.scriptamat.2019.10.006}
}
|
| Rahul M and Phanikumar G (2020), "Solidification behaviour of undercooled equiatomic FeCuNi alloy", Journal of Alloys and Compounds. Vol. 815, pp. 152334. |
| Abstract: Studies on solidification of equiatomic multi-component alloys are essential in developing melt-route processing of high entropy alloys. The extent of undercooling during processing controls microstructure evolution. In this study, we present solidification studies on undercooled equiatomic FeCuNi alloy carried out using melt fluxing technique. The alloy shows a two-phase (FCC + FCC) microstructure even at deep undercooling of more than 200 K. The dendrite growth velocity measured using high-speed video imaging shows a nonlinear increase in growth velocity with the increase in the extent of undercooling. A modified dendritic growth model was able to predict the growth velocity. The segregation behaviour and microstructures at different extents of undercooling can be predicted using phase field simulation. |
BibTeX:
@article{Rahul2020b,
author = {M.R. Rahul and Gandham Phanikumar},
title = {Solidification behaviour of undercooled equiatomic FeCuNi alloy},
journal = {Journal of Alloys and Compounds},
year = {2020},
volume = {815},
pages = {152334},
url = {https://www.sciencedirect.com/science/article/pii/S0925838819335807},
doi = {10.1016/j.jallcom.2019.152334}
}
|
| Rahul M and Phanikumar G (2020), "Experimental and simulation studies of solidification behavior in undercooled CuCoNi equiatomic medium entropy alloy", The European Physical Journal Special Topics. Vol. 229(2-3), pp. 145-155. |
| Abstract: Undercooling studies were carried out in equiatomic CuCoNi system with an aim to understand the growth kinetics and microstructural variations as a function of undercooling. The morphological change in microstructure was observed and correlated with the undercooling obtained. Non-linear variation of growth velocity with respect to the increase in undercooling was obtained from high-speed video measurements. The variation in growth velocity was compared with the dendritic growth model with a modified kinetic undercooling term. The segregation profile was predicted using multi-phase field method and compared with the experimental data. Micro-hardness variation was correlated with the undercooling obtained. |
BibTeX:
@article{Rahul2020c,
author = {M.R. Rahul and Gandham Phanikumar},
title = {Experimental and simulation studies of solidification behavior in undercooled CuCoNi equiatomic medium entropy alloy},
journal = {The European Physical Journal Special Topics},
year = {2020},
volume = {229},
number = {2--3},
pages = {145--155},
url = {https://link.springer.com/article/10.1140%2Fepjst%2Fe2019-900111-5},
doi = {10.1140/epjst/e2019-900111-5}
}
|
| Rahul M and Phanikumar G (2020), "Growth kinetics, microhardness and microstructure evolution of undercooled FeCoNiCuSn high entropy alloy", Materials Science and Engineering A. Vol. 777, pp. 139022. |
| Abstract: Multi-principle element alloy FeCoNiCu with varying Sn addition was undercooled using the meltfluxing technique to illustrate the dependence of growth kinetics on Sn addition. The alloy FeCoNiCuSn0.5 shows morphological variation in the microstructure from dendritic to equiaxed grain morphology with the increase in undercooling. The alloy FeCoNiCuSn5 shows dendrite morphology with undercooling. The dendritic growth velocity was sluggish with solute addition,i.e., at an undercooling of 200 K, the growth velocity decreased from 25 m/s to 6 m/s while varying Sn concentration from 0.5 to 5 at % suggesting solute drag effect. The microhardness improvement could be correlated to the microstructure refinement achieved during undercooling. |
BibTeX:
@article{Rahul2020d,
author = {M.R. Rahul and G. Phanikumar},
title = {Growth kinetics, microhardness and microstructure evolution of undercooled FeCoNiCuSn high entropy alloy},
journal = {Materials Science and Engineering A},
year = {2020},
volume = {777},
pages = {139022},
url = {https://www.sciencedirect.com/science/article/pii/S0921509320301118},
doi = {10.1016/j.msea.2020.139022}
}
|
| Agilan M, Phanikumar G and Sivakumar D (2019), "Mechanical Properties and Microstructural Evolution in Al-Cu-Li 2195 Alloy GTA and FWS Welds", Indian Welding Journal., 04, 2019. Vol. 52, pp. 53-58. |
BibTeX:
@article{Agilan2019,
author = {M Agilan and G Phanikumar and D Sivakumar},
title = {Mechanical Properties and Microstructural Evolution in Al-Cu-Li 2195 Alloy GTA and FWS Welds},
journal = {Indian Welding Journal},
year = {2019},
volume = {52},
pages = {53--58},
url = {http://www.i-scholar.in/index.php/IWJ/article/view/186789},
doi = {10.22486/iwj.v52i4.186789}
}
|
| Farivar H, Deepu M, Hans M, Phanikumar G, Bleck W and Prahl U (2019), "Influence of post-carburizing heat treatment on the core microstructural evolution and the resulting mechanical properties in case-hardened steel components", Materials Science and Engineering A. Vol. 744, pp. 778-789. |
| Abstract: The case hardening process (carburizing followed by quenching to room temperature) is one of the heat treatments routinely conducted in various industrial sectors. Depending on the parameters applied during the post-carburizing stage, different microstructural constituents may develop in the interior (core) section of a case-hardened component which substantially influence the overall mechanical properties. In the present work, the effects of different heat treatments following the carburizing stage on the core microstructure evolution, the resulting toughness and hardness properties were investigated. The heat treatments were carried out employing Navy C-ring specimens, the core of which were used for microstructural investigations and fabrication of mini-Charpy specimens. Besides, nanoindentation tests were also carried out in the same region to examine the local hardness of different constituents. Furthermore, the microstructural evolutions were also studied utilizing multi-phase field modeling. Based on the obtained results, it can be shown that the increase in fractions of bainite and retained austenite is in direct correlation with the impact toughness improvement, however, the increase in fraction of ferrite and martensite acts inversely. Moreover, despite the differences in fractions of constituents, the level of overall hardness is similar in all the developed microstructures. Additionally, the nanoindentation results revealed that the formation of large fraction of bainitic ferrite leads to high level of scattering in nanohardness of martensite. Phase field simulations show that this is attributed to the degree of carbon partitioning into the adjacent austenitic area where depending on the local morphology and size can be quite different. |
BibTeX:
@article{FarivarH.2019,
author = {Farivar H. and Deepu, M.J. and Hans, M. and Phanikumar, G and Bleck W. and Prahl, U.},
title = {Influence of post-carburizing heat treatment on the core microstructural evolution and the resulting mechanical properties in case-hardened steel components},
journal = {Materials Science and Engineering A},
year = {2019},
volume = {744},
pages = {778--789},
url = {https://www.sciencedirect.com/science/article/pii/S0921509318317404},
doi = {10.1016/j.msea.2018.12.061}
}
|
| Rahul M, Samal S and Phanikumar G (2019), "Hot Deformation Behavior and Microstructural Characterization of CoCrFeNiNb0.45 Eutectic High Entropy Alloy", Materials Performance and Characterization. Vol. 8(5), pp. 1062-1075. |
| Abstract: In recent years, several multicomponent alloys of near equiatomic composition (also known as high-entropy alloys) with excellent mechanical properties have been developed. In this study, a eutectic high entropy alloy, CoCrFeNiNb0.45, was chosen for a hot deformation study. The alloy consists of a primary face-centered cubic (FCC) phase (CoCrFeNi rich) and a eutectic region between the FCC and Laves phase (Co2Nb type). The combination of FCC and eutectic region is expected to provide better strength and ductility. Hot compression tests were carried out at different strain rates of 0.001, 0.1, 1, and 10 s−1 with varying temperatures of 1,073, 1,173, 1,273, and 1,323 K. The optimum processing window was identified by plotting processing maps, and the instability region was verified using multiple parameters. Constitutive equation relating stress, strain rate, and temperature is established. The optimum processing condition was correlated with the microstructural characterization, and instability was characterized with cracks on the specimen. Finite element simulation was carried out, taking the flow curve as input and correlating the strain field distribution with the microhardness variation. These studies are intended to contribute to an integrated computational materials engineering approach to developing these alloys toward a product. |
BibTeX:
@article{M.Rahul2019,
author = {M. Rahul and S. Samal and G. Phanikumar},
title = {Hot Deformation Behavior and Microstructural Characterization of CoCrFeNiNb0.45 Eutectic High Entropy Alloy},
journal = {Materials Performance and Characterization},
year = {2019},
volume = {8},
number = {5},
pages = {1062--1075},
url = {https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/MPC/PAGES/MPC20190014.htm},
doi = {10.1520/MPC20190014}
}
|
| Sankar M, Phanikumar G and Prasad V (2019), "Effect of Zr addition on the mechanical properties of NbSi based alloys", Materials Science and Engineering A. Vol. 754, pp. 224-231. |
| Abstract: In the present study, the effect of Zr addition on the mechanical properties of arc melted hypoeutectic Nb−16 at. %Si alloy has been investigated. The alloys were characterized by scanning electron microscopy (SEM), electron back scattered diffraction (EBSD), hardness test, nanoindentation test, compression test and three point bend test. The desirable phase α−Nb5Si3 phase could be obtained in alloys containing 4 at. % or more Zr. Nanoindentation results showed that the elastic modulus of Nbss phase is not significantly influenced by Zr additions whereas elastic modulus of Nb3Si and α−Nb5Si3phases are considerably improved by Zr additions. The strength, plasticity and room temperature fracture toughness of the alloys are significantly increased with Zr addition. The maximum compressive strength of 2160 ± 80 MPa, plastic strain of 2.6 ± 0.2% and fracture toughness of 14.3 ± 0.3MPam1/2are achieved in alloy with 4 at.% Zr. |
BibTeX:
@article{M.Sankar2019,
author = {M. Sankar and G. Phanikumar and V.V.S. Prasad},
title = {Effect of Zr addition on the mechanical properties of NbSi based alloys},
journal = {Materials Science and Engineering A},
year = {2019},
volume = {754},
pages = {224--231},
url = {https://www.sciencedirect.com/science/article/pii/S0921509319303879},
doi = {10.1016/j.msea.2019.03.078}
}
|
| Mohan D and Phanikumar G (2019), "Experimental and modelling studies for solidification of undercooled Ni–Fe–Si alloys", Philosophical Transactions of the Royal Society A. Vol. 377, pp. 20180208. |
BibTeX:
@article{Mohan2019,
author = {Dasari Mohan and Gandham Phanikumar},
title = {Experimental and modelling studies for solidification of undercooled Ni–Fe–Si alloys},
journal = {Philosophical Transactions of the Royal Society A},
year = {2019},
volume = {377},
pages = {20180208},
url = {https://royalsocietypublishing.org/doi/10.1098/rsta.2018.0208},
doi = {10.1098/rsta.2018.0208}
}
|
| Muthumanickam A, Gandham P and Dhenuvakonda S (2019), "Effect of Friction Stir Welding Parameters on Mechanical Properties and Microstructure of AA2195 Al–Li Alloy Welds", Transactions of the Indian Institute of Metals. Vol. 72, pp. 1557-1561. |
| Abstract: In this paper, effect of friction stir welding process parameters on mechanical properties and microstructure of AA2195 welds were studied. Five levels of tool rotation speed from 400 to 1000 rpm and three levels of travel speed from 100 to 300 mm/min were considered. These parameters affected heat input generation in the welds, thereby influencing stir zone geometry, grain size evolution in stir zone, tensile properties and hardness of the weld. Low tool rotation speed and high travel speed resulted in finer grain size. Travel speed significantly affected the tensile properties compared to rotation speed. Processing window to achieve defect-free welds was identified, and maximum weld efficiency was obtained at 400 rpm rotation speed and 300 mm/min travel speed. |
BibTeX:
@article{Muthumanickam2019,
author = {Agilan Muthumanickam and Phanikumar Gandham and Sivakumar Dhenuvakonda},
title = {Effect of Friction Stir Welding Parameters on Mechanical Properties and Microstructure of AA2195 Al–Li Alloy Welds},
journal = {Transactions of the Indian Institute of Metals},
year = {2019},
volume = {72},
pages = {1557--1561},
url = {https://link.springer.com/article/10.1007/s12666-019-01570-x},
doi = {10.1007/s12666-019-01570-x}
}
|
| Rahul M and Phanikumar G (2019), "Design of a seven-component eutectic high-entropy alloy", Metallurgical and Materials Transactions A. Vol. 50(6), pp. 2594-2598. |
| Abstract: A eutectic high-entropy alloy with seven components (Fe, Ni, Cr, V, Co, Mn, and Nb) was designed via the melt route guided by CALPHAD predictions. Configurational entropy estimated for the two-phase microstructure qualifies it to be referred to as a high-entropy alloy. When the Nb content exceeded 9.7 at. pct, the microstructure changed from hypoeutectic with primary face-centered cubic phase to hypereutectic with primary Laves phase. |
BibTeX:
@article{Rahul2019,
author = {M.R. Rahul and G. Phanikumar},
title = {Design of a seven-component eutectic high-entropy alloy},
journal = {Metallurgical and Materials Transactions A},
year = {2019},
volume = {50},
number = {6},
pages = {2594--2598},
url = {https://link.springer.com/article/10.1007/s11661-019-05210-3},
doi = {10.1007/s11661-019-05210-3}
}
|
| Rahul MR, Samal S and Phanikumar G (2019), "Effect of niobium addition in FeCoNiCuNbx high-entropy alloys", Journal of Materials Research. Vol. 34(5), pp. 700-708. |
| Abstract: In the design of high-entropy alloys (HEAs) with desired properties, identifying the effects of elements plays an important role. HEAs with eutectic microstructure can be obtained by judiciously modifying the alloy compositions. In this study, the effect of Nb addition to FeCoNiCuNbx (x = 0.5, 5, 7.5, 11.6, 15) alloys was studied by varying the Nb concentration (at.%). FeCoNiCuNb0.5 HEA shows liquid phase separation to form Cu-rich and FeCoNiCu-rich phases. Detailed solidification paths are proposed for these alloys, which show eutectic, peritectic, and pseudo quasi-peritectic reactions. Increasing Nb content promotes the liquid phase separation tendency and causes the formation of Cu-rich spheres. The effect of Nb on the FeCoNiCu-rich phase was studied based on the nanoindentation and correlated with nanohardness. The compressive deformation properties of these alloys are studied at room temperature and high temperature and correlated with microstructure. Fractography results show the mode of fracture and are correlated with the microstructure obtained. |
BibTeX:
@article{RahulM.R.2019,
author = {Rahul M.R. and Sumanta Samal and Gandham Phanikumar},
title = {Effect of niobium addition in FeCoNiCuNbx high-entropy alloys},
journal = {Journal of Materials Research},
year = {2019},
volume = {34},
number = {5},
pages = {700--708},
url = {https://www.cambridge.org/core/product/87EA53C9E940F5896C7B31632D5D990A/core-reader},
doi = {10.1557/jmr.2019.36}
}
|
| Agilan M, Phanikumar G and Sivakumar D (2018), "Weld Solidification Cracking Behaviour of AA2195 Al–Cu–Li Alloy", Transactions of the Indian Institute of Metals. Vol. 71, pp. 2667-2670. |
| Abstract: In this study, weld solidification cracking behaviour of AA2195 Al–Cu–Li alloy was studied and compared with conventional AA2219 and AA2014 aluminium alloys. Cracking susceptibility was evaluated using varestraint test and Gleeble® hot ductility test and the slope of liquidus temperature as function of liquid fraction was also evaluated. Solidification cracking susceptibility of AA2195, AA2219 and AA2014 alloys was ranked based on the above methods. Consistent trend in cracking susceptibility was observed in all the methods where AA2195 and AA2219 alloys showed highest and lowest cracking susceptibility, respectively. |
BibTeX:
@article{Agilan2018,
author = {Agilan, M. and Phanikumar, G. and Sivakumar, D.},
title = {Weld Solidification Cracking Behaviour of AA2195 Al–Cu–Li Alloy},
journal = {Transactions of the Indian Institute of Metals},
year = {2018},
volume = {71},
pages = {2667--2670},
url = {https://link.springer.com/article/10.1007%2Fs12666-018-1425-6},
doi = {10.1007/s12666-018-1425-6}
}
|
| M.Sankar, G.Phanikumar, VajinderSingh and Prasad V (2018), "Effect of Zr additions on microstructure evolution and phase formation of Nb−Si based ultrahigh temperature alloys", Intermetallics. Vol. 101, pp. 123-132. |
| Abstract: In the present work, the role of Zr addition on the microstructure and phase formation of hypoeutectic Nb−16 at. % Si alloy has been investigated. The results showed that both binary and alloy with 2 at. % Zr resulted in two phase microstructures composed of Nbss and Nb3Si phases. In contrast, the alloys with 4 at. % Zr and 6 at. % Zr revealed two phase microstructures composed of Nbss and α−Nb5Si3 phases. The orientation relationship (OR) obtained between eutectoid lamellar structure comprising of Nbss and α−Nb5Si3 phases is (110) Nb//(110) Nb5Si3. The equilibrium microstructures consisting of Nb and α−Nb5Si3 phases were obtained in as cast condition when the Zr concentration is above 2 at.%. The addition of Zr accelerated the dissociation kinetics of Nb3Si phase in to Nbss and α−Nb5Si3 phases during solidification. The formation of α−Nb5Si3 phase in the as cast condition eliminates heat treatment required for decomposition of Nb3Si phase in Nb-Si alloys. |
BibTeX:
@article{M.Sankar2018,
author = {M.Sankar and G.Phanikumar and VajinderSingh and V.V.Satya Prasad},
title = {Effect of Zr additions on microstructure evolution and phase formation of Nb−Si based ultrahigh temperature alloys},
journal = {Intermetallics},
year = {2018},
volume = {101},
pages = {123--132},
url = {https://www.sciencedirect.com/science/article/pii/S0966979518302371},
doi = {10.1016/j.intermet.2018.07.010}
}
|
| Nithin B, Chattopadhyay K and Phanikumar G (2018), "Characterization of the Hot Deformation Behavior and Microstructure Evolution of a New γ-γ′ Strengthened Cobalt-Based Superalloy", Metallurgical and Materials Transactions A. Vol. 49, pp. 4895-4905. |
| Abstract: Recently, cobalt-based γ-γ′ microstructured superalloys have attracted attention. However, studies on their processing behavior [i.e., processing maps (the variation of strain rate sensitivity (m) with temperature)] are limited. Thus, the high-temperature flow behavior of a γ-γ′ Co-30Ni-10Al-5Mo-2Ta-2Ti-5Cr (at. pct) superalloy was investigated using isothermal compression tests between 1348 and 1498 K at strain rates from 0.001 to 10 s−1. The m contour map was generated using the experimental flow stress values, which were used to locate the optimum hot workability and desired microstructural processing range. A strong dependence of m on the deformation parameters (temperature, strain rate, and strain) was observed. A maximum m value of around 0.3 at 1460 K to 1498 K and strain rates of 0.01 to 0.5 s−1 was found. The deformed samples show a fully recrystallized microstructure at high m. Unstable domains showed the formation of cavities at the grain boundary triple points and cracks along the grain boundaries at high strain rates (1 to 10 s−1), corresponding to m < 0.10. A constitutive model was developed using an Arrhenius hyperbolic sine function, yielding an apparent activation energy of 540 ± 30 kJ mol−1 for hot deformation. This study indicates reasonable formability under certain conditions below the solvus, thus opening possibilities for further thermomechanical treatment. |
BibTeX:
@article{Nithin2018,
author = {Nithin, B. and Chattopadhyay, K and Phanikumar, G.},
title = {Characterization of the Hot Deformation Behavior and Microstructure Evolution of a New γ-γ′ Strengthened Cobalt-Based Superalloy},
journal = {Metallurgical and Materials Transactions A},
year = {2018},
volume = {49},
pages = {4895--4905},
url = {https://link.springer.com/article/10.1007%2Fs11661-018-4795-9},
doi = {10.1007/s11661-018-4795-9}
}
|
| Rahul M, Samal S, Venugopal S and Phanikumar G (2018), "Experimental and finite element simulation studies on hot deformation behaviour of AlCoCrFeNi2. 1 eutectic high entropy alloy", Journal of Alloys and Compounds. Vol. 749, pp. 1115-1127. |
| Abstract: Hot deformation behaviour of AlCoCrFeNi2.1 eutectic high entropy alloy, consisting of fcc (CoCrFe-rich) and BCC (NiAl-rich) phases is studied by generating contour maps of multiple models using high temperature thermo-mechanical simulator compression test data. The workability regimes for thermomechanical processing are identified as 1073–1150 K and 10−3– 10−2.2s−1 as well as 1338–1373 K and 10−3–10−1.2 s−1. Finite element simulation has been used to study the strain distribution and material flow during hot deformation, which assists for predicting actual material flow in forging process. Flow instabilities during hot forming has been avoided by adopting integrated approach. |
BibTeX:
@article{Rahul2018,
author = {MR Rahul and S Samal and S Venugopal and G Phanikumar},
title = {Experimental and finite element simulation studies on hot deformation behaviour of AlCoCrFeNi2. 1 eutectic high entropy alloy},
journal = {Journal of Alloys and Compounds},
year = {2018},
volume = {749},
pages = {1115--1127},
url = {https://www.sciencedirect.com/science/article/pii/S0925838818311332},
doi = {10.1016/j.jallcom.2018.03.262}
}
|
| Rahul M, Samal S and Phanikumar G (2018), "Undercooling studies and growth velocity measurements on multi- component FeCuNiX alloys", In Solidification and Gravity VII. , pp. 250-254. Hungarian Academy of Sciences – University of Miskolc, Materials Science Research Group. |
BibTeX:
@inproceedings{Rahul2018a,
author = {M.R. Rahul and Sumanta Samal and Gandham Phanikumar},
editor = {A. Roósz, Zs. Veres, M. Svéda, G. Karacs},
title = {Undercooling studies and growth velocity measurements on multi- component FeCuNiX alloys},
booktitle = {Solidification and Gravity VII},
publisher = {Hungarian Academy of Sciences – University of Miskolc, Materials Science Research Group},
year = {2018},
pages = {250--254},
note = {ISBN: 978-963-508-889-8},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Rahul_SolidificationGravity2018a.pdf}
}
|
| Rahul M, Jain R, Samal S and Phanikumar G (2018), "Microstructure evolution and mechanical properties of Co-Fe-Ni-Ti-V eutectic high entropy alloy", In Solidification and Gravity VII. , pp. 313-318. Hungarian Academy of Sciences - University of Miskolc, Materials Science Research Group. |
BibTeX:
@inproceedings{Rahul2018b,
author = {M.R. Rahul, Reliance Jain, Sumanta Samal, Gandham Phanikumar},
editor = {A. Roósz, Zs. Veres, M. Svéda, G. Karacs},
title = {Microstructure evolution and mechanical properties of Co-Fe-Ni-Ti-V eutectic high entropy alloy},
booktitle = {Solidification and Gravity VII},
publisher = {Hungarian Academy of Sciences - University of Miskolc, Materials Science Research Group},
year = {2018},
pages = {313--318},
note = {ISBN: 978-963-508-889-8},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Rahul_SolidificationGravity2018b.pdf}
}
|
| Babu A, John DM and Phanikumar G (2017), "An attempt to incorporate the effect of microstructure on the macroscale simulation of heat transfer during heat treatment in multi component dual phase steel", In Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017). , pp. 2365-2370. |
| Abstract: Dual phase steel is one of the future materials for automobile industry, as it shows a combination of high strength and adequate formability. Studies have shown that it has the potential to occupy up to 80% of the total weight of a car. Residual stress during heat treatments is one of the issues that need to be studied in dual phase steel and computational simulations can help in reducing the experimental trials required for such a study. The heat transfer simulation in such a material is challenging, as it involves phase transformation at the microscale. In the present work, an attempt is made to incorporate the effect of phase transformation at the microscale while simulating the macroscale heat transfer and consequent residual stress. A novel and simple flat geometry is chosen for study that helps in easy measurement of residual stresses. The geometry is a rectangular strip with an elliptical hole and the role played by the angle of elliptical hole on residual stress prediction is discussed. Finite Element simulation of the heat transfer and the subsequent residual stress is performed using the commercial software Simufact Forming®. The effect of microscale phase transformations on the residual stress was considered during the software simulations. These simulations are validated using physical simulations in Gleeble® and measurement of macroscale residual stress with X-Ray diffraction technique. |
BibTeX:
@inproceedings{Babu2017,
author = {Aravind Babu and Deepu Mathew John and Gandham Phanikumar},
title = {An attempt to incorporate the effect of microstructure on the macroscale simulation of heat transfer during heat treatment in multi component dual phase steel},
booktitle = {Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017)},
year = {2017},
pages = {2365-2370},
url = {https://mme.iitm.ac.in/gphani/assets/publications/IHMTC2017-18-0373.pdf}
}
|
| John DM, Farivar H, Prahl U and Phanikumar G (2017), "Microstructure based simulations for prediction of flow curves and selection of process parameters for inter-critical annealing in DP steel", IOP Conference Series: Materials Science and Engineering. , pp. 012010. |
BibTeX:
@article{Deepu2017,
author = {Deepu Mathew John and Hamid Farivar and Ulrich Prahl and Gandham Phanikumar},
title = {Microstructure based simulations for prediction of flow curves and selection of process parameters for inter-critical annealing in DP steel},
journal = {IOP Conference Series: Materials Science and Engineering},
year = {2017},
pages = {012010},
url = {http://iopscience.iop.org/article/10.1088/1757-899X/192/1/012010/meta}
}
|
| John DM, Farivar H, Rothenbucher G, Kumar R, Zagade P, Khan D, Babu A, Gautham B, Bernhardt R, Phanikumar G and Prahl U (2017), "An Attempt to Integrate Software Tools at Microscale and Above Towards an ICME Approach for Heat Treatment of a DP Steel Gear with Reduced Distortion", In Proceedings of the 4th World Congress on Integrated Computational Materials Engineering (ICME 2017). , pp. 3-13. Spinger. |
BibTeX:
@inproceedings{John2017,
author = {Deepu Mathew John and Hamidreza Farivar and Gerald Rothenbucher and Ranjeet Kumar and Pramod Zagade and Danish Khan and Aravind Babu and BP Gautham and Ralph Bernhardt and G Phanikumar and Ulrich Prahl},
title = {An Attempt to Integrate Software Tools at Microscale and Above Towards an ICME Approach for Heat Treatment of a DP Steel Gear with Reduced Distortion},
booktitle = {Proceedings of the 4th World Congress on Integrated Computational Materials Engineering (ICME 2017)},
publisher = {Spinger},
year = {2017},
pages = {3--13},
url = {https://par.nsf.gov/servlets/purl/10057775#page=17},
doi = {10.1007/978-3-319-57864-4_1}
}
|
| Chandra S, Phanikumar G, Seet GL, Tor SB and Chua CK (2016), "Multi-scale modeling of additive manufacturing process", In Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016). , pp. 543-550. |
BibTeX:
@inproceedings{Chandra2016,
author = {Chandra, Shubham and Phanikumar, Gandham and Seet, Gim Lee and Tor, Shu Beng and Chua, Chee Kai},
title = {Multi-scale modeling of additive manufacturing process},
booktitle = {Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016)},
year = {2016},
pages = {543--550},
url = {http://hdl.handle.net/10220/41778}
}
|
| Nath H and Phanikumar G (2016), "Microstructural, Magnetic and Electrical Properties of Ni2FeGa Heusler Alloys", Transactions of the Indian Institute of Metals. Vol. 69, pp. 1389-1396. |
BibTeX:
@article{Nath2015b,
author = {Hrusikesh Nath and G. Phanikumar},
title = {Microstructural, Magnetic and Electrical Properties of Ni2FeGa Heusler Alloys},
journal = {Transactions of the Indian Institute of Metals},
year = {2016},
volume = {69},
pages = {1389--1396},
url = {http://link.springer.com/article/10.1007%2Fs12666-015-0691-9},
doi = {10.1007/s12666-015-0691-9}
}
|
| Renil THomas K, Unnikrishnakurup S, Balasubramaniam K, Narayanan L and Phanikumar G (2016), "Dissimilar metal joint quality measurement using infrared thermometry: Experimental and Numerical approach for the application to CMT welding", In Proceedings of the 13th Quantitative InfraRed Thermography (QIRT 2016). QIRT Council. |
BibTeX:
@inproceedings{RenilTHomas2016,
author = {Renil THomas K and Sreedhar Unnikrishnakurup and Krishnan Balasubramaniam and Lakshmi Narayanan and Phanikumar G},
editor = {QIRT Council},
title = {Dissimilar metal joint quality measurement using infrared thermometry: Experimental and Numerical approach for the application to CMT welding},
booktitle = {Proceedings of the 13th Quantitative InfraRed Thermography (QIRT 2016)},
publisher = {QIRT Council},
year = {2016},
url = {http://qirt.org/archives/qirt2016/papers/056.pdf},
doi = {10.21611/qirt.2016.056}
}
|
| Samal S, Rahul MR, Kottada RS and Phanikumar G (2016), "Hot deformation behaviour and processing map of Co-Cu-Fe-Ni-Ti eutectic high entropy alloy", Materials Science and Engineering A. Vol. 664, pp. 227-235. |
BibTeX:
@article{Samal2016,
author = {Sumanta Samal and M. R. Rahul and Ravi Sankar Kottada and Gandham Phanikumar},
title = {Hot deformation behaviour and processing map of Co-Cu-Fe-Ni-Ti eutectic high entropy alloy},
journal = {Materials Science and Engineering A},
year = {2016},
volume = {664},
pages = {227--235},
url = {http://www.sciencedirect.com/science/article/pii/S0921509316303677},
doi = {10.1016/j.msea.2016.04.006}
}
|
| Samal S, Biswas K and Phanikumar G (2016), "Solidification Behavior in Newly Designed Ni-Rich Ni-Ti-Based Alloys", Metallurgical and Materials Transactions A. Vol. 47, pp. 6214-6223. |
| Abstract: The present investigation reports phase and microstructure evolution during solidification of novel Ni-rich Ni-Ti-based alloys, Ni60Ti40, Ni50Cu10Ti40, Ni48Cu10Co2Ti40, and Ni48Cu10Co2Ti38Ta2 during suction casting. The design philosophy of the multicomponent alloys involves judicious selection of alloying elements such as Cu, Co, and Ta in the near Ni60Ti40 eutectic alloy by replacing both Ni and Ti so that phase mixture in the microstructure remains the same from the binary to quinary alloy. The basic objective is to study the effect of addition of Cu, Co, and Ta on the phase evolution and transformation in the Ni-rich Ni-Ti-based alloys. The detailed electron microscopic studies on these suction cast alloys reveal the presence of ultrafine eutectic lamellae between NiTi and Ni3Ti phases along with dendritic NiTi and Ti2Ni phases. It has also been observed that in the binary (Ni60Ti40) alloy, the ordered NiTi (B2) phase transforms to trigonal (R) phase followed by NiTi martensitic phase (M-phase), i.e., B2 → R-phase → M-phase during solid-state cooling. However, the addition of alloying elements such as Cu, Co to the binary (Ni60Ti40) alloy suppresses the martensitic transformation of the ordered NiTi (B2) dendrite. Thus, in the ternary and quaternary alloys, the ordered NiTi (B2) phase is transformed to only trigonal (R) phase, i.e., B2 → R-phase. The secondary precipitate of Ti2Ni has been observed in all of the studied alloys. Interestingly, Ni48Cu10Co2Ti38Ta2 quinary alloy shows the disordered nature of NiTi dendrites. The experimentally observed solidification path is in good agreement with Gulliver–Scheil simulated path for binary alloy, whereas simulated solidification path deviates from the experimental results in case of ternary, quaternary, and quinary alloys. |
BibTeX:
@article{Samal2016a,
author = {Sumanta Samal and Krishanu Biswas and G. Phanikumar},
title = {Solidification Behavior in Newly Designed Ni-Rich Ni-Ti-Based Alloys},
journal = {Metallurgical and Materials Transactions A},
year = {2016},
volume = {47},
pages = {6214--6223},
url = {http://link.springer.com/article/10.1007%2Fs11661-016-3789-8},
doi = {10.1007/s11661-016-3789-8}
}
|
| Sankar M, Phanikumar G and Prasad V (2016), "Effect of Alloying Additions and Heat Treatment on the Microstructure Evolution of Nb-16Si Alloy", Materials Today: Proceedings. Vol. 3, pp. 3094-3103. |
BibTeX:
@article{Sankar2016,
author = {Sankar, M. and G. Phanikumar and Prasad, V.V.S.},
title = {Effect of Alloying Additions and Heat Treatment on the Microstructure Evolution of Nb-16Si Alloy},
journal = {Materials Today: Proceedings},
year = {2016},
volume = {3},
pages = {3094--3103},
doi = {10.1016/j.matpr.2016.09.025}
}
|
| Gerald Tennyson P, Karthik G and Phanikumar G (2015), "MPI + OpenCL implementation of a phase-field method incorporating CALPHAD description of Gibbs energies on heterogeneous computing", Computer Physics Communications. Vol. 186, pp. 48-64. |
BibTeX:
@article{GeraldTennyson2015,
author = {Gerald Tennyson, P. and Karthik, G.M. and Phanikumar, G},
title = {MPI + OpenCL implementation of a phase-field method incorporating CALPHAD description of Gibbs energies on heterogeneous computing},
journal = {Computer Physics Communications},
year = {2015},
volume = {186},
pages = {48--64},
doi = {10.1016/j.cpc.2014.09.014}
}
|
| Rahul M and Phanikumar G (2015), "Correlation of Microstructure With HAZ Welding Cycles Simulated in Ti-15-3 Alloy Using Gleeble 3800 and SYSWELD", Materials Performance and Characterization. |
BibTeX:
@article{Hru2015b,
author = {Rahul, M.R. and Phanikumar, Gandham},
title = {Correlation of Microstructure With HAZ Welding Cycles Simulated in Ti-15-3 Alloy Using Gleeble 3800 and SYSWELD},
journal = {Materials Performance and Characterization},
year = {2015},
url = {http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/MPC/PAGES/MPC20140065.htm},
doi = {10.1520/MPC20140065}
}
|
| Nath H and Phanikumar G (2015), "Premartensite transition in Ni2FeGa Heusler alloy", Materials Characterization. Vol. 102, pp. 24-28. |
BibTeX:
@article{Nath2015,
author = {Hrusikesh Nath and Phanikumar, G},
title = {Premartensite transition in Ni2FeGa Heusler alloy},
journal = {Materials Characterization},
year = {2015},
volume = {102},
pages = {24--28},
doi = {10.1016/j.matchar.2015.02.012}
}
|
| Nath H and Phanikumar G (2015), "Martensite transformation and magnetic properties of Ni-Fe-Ga Heusler alloys", Metallurgical and Materials Transactions A. Vol. 46A, pp. 4947. |
BibTeX:
@article{Nath2015a,
author = {Hrusikesh Nath and G. Phanikumar},
title = {Martensite transformation and magnetic properties of Ni-Fe-Ga Heusler alloys},
journal = {Metallurgical and Materials Transactions A},
year = {2015},
volume = {46A},
pages = {4947},
url = {http://link.springer.com/article/10.1007/s11661-015-3098-7},
doi = {10.1007/s11661-015-3098-7}
}
|
| Ramakrishnan R, Phanikumar G and Sankarasubramanian R (2015), "Crystal-melt interface growth velocity of Ni-Zr alloys through molecular dynamics simulations", Transactions of the Indian Institute of Metals. |
BibTeX:
@article{R.Ramakrishnan2015,
author = {R. Ramakrishnan and G. Phanikumar and R. Sankarasubramanian},
title = {Crystal-melt interface growth velocity of Ni-Zr alloys through molecular dynamics simulations},
journal = {Transactions of the Indian Institute of Metals},
year = {2015},
url = {http://link.springer.com/article/10.1007/s12666-015-0655-0},
doi = {10.1007/s12666-015-0655-0}
}
|
| Samal S and Phanikumar G (2015), "Phase evolution in hypereutectic Al90Cu10-xNix (x=0,5) alloys", Transactions of the Indian Institute of Metals. Vol. 68(6), pp. 1221-1226. |
BibTeX:
@article{Samal2015,
author = {Sumanta Samal and G. Phanikumar},
title = {Phase evolution in hypereutectic Al90Cu10-xNix (x=0,5) alloys},
journal = {Transactions of the Indian Institute of Metals},
year = {2015},
volume = {68},
number = {6},
pages = {1221--1226},
url = {http://link.springer.com/article/10.1007/s12666-015-0709-3},
doi = {10.1007/s12666-015-0709-3}
}
|
| Kala S, Siva Prasad N and Phanikumar G (2014), "Studies on multipass welding with trailing heat sink considering phase transformation", Journal of Materials Processing Technology. Vol. 214(6), pp. 1228-1235. |
| Abstract: A two pass butt welding of 6 mm mild steel plates was simulated using 3D finite element model using temperature and phase dependent material properties. Material phase transformations were simulated using suitable phase transformation kinetic models. Mechanical analysis is carried out using nodal temperature and phase proportions as input. Experiments were carried out using liquid nitrogen (LN2) as trailing heat sink. Trailing heat sink helped to reduce the residual stress in the fusion zone (FZ) and heat affected zone (HAZ) although distortions were found be increasing. A parametric study was conducted to study the effect of distance between weld arc and trailing heat sink. The heat sink closer to weld arc reduced both distortions and residual stresses. © 2014 Published by Elsevier B.V. |
BibTeX:
@article{Kala2014,
author = {Kala, S.R. and Siva Prasad, N. and Phanikumar, G.},
title = {Studies on multipass welding with trailing heat sink considering phase transformation},
journal = {Journal of Materials Processing Technology},
year = {2014},
volume = {214},
number = {6},
pages = {1228-1235},
note = {cited By (since 1996)0},
url = {https://www.sciencedirect.com/science/article/pii/S0924013614000223},
doi = {10.1016/j.jmatprotec.2014.01.008}
}
|
| Kala S, Prasad N and Phanikumar G (2014), "Numerical study of welding with trailing heat sink considering phase transformation effects", Advanced Materials Research. Vol. 875-877, pp. 2118-2122. |
| Abstract: Welding process with trailing heat sink for 2 mm mild steel plates has been analyzed to estimate distortion and residual stresses using a finite element modeling software Sysweld. The material properties used for the analysis are both temperature dependent and phase dependent. A transient thermal analysis is carried out using Goldak double ellipsoidal heat source model and heat sink as Gaussian model with negative heat flux. The finite element analysis (FEA) is conducted by considering the material properties of all phases of steel as well as without phase transformation i.e. by considering properties of only ferrite phase. Temperature distribution, distortion and residual stresses are calculated and compared for four cases: without phase without cooling, without phase with cooling, with phase without cooling and with phase with cooling. It is found that FEA without phase transformation effects overestimates the residual stresses in the fusion zone (FZ) and heat affected zone (HAZ). It is also found that a trailing heat sink reduces transverse compressive residual stresses thus minimizing the possibilities of buckling. © (2014) Trans Tech Publications, Switzerland. |
BibTeX:
@article{Kala2014a,
author = {Kala, S.R. and Prasad, N.S. and Phanikumar, G.},
title = {Numerical study of welding with trailing heat sink considering phase transformation effects},
journal = {Advanced Materials Research},
year = {2014},
volume = {875-877},
pages = {2118-2122},
note = {cited By (since 1996)0},
url = {https://www.scientific.net/AMR.875-877.2118},
doi = {10.4028/www.scientific.net/AMR.875-877.2118}
}
|
| Nath H and Phanikumar G (2014), "Microstructure and Phase Evolution of Ni2FeGa Heusler Alloy Extended to Different Degrees of Undercooling", Materials Science Forum. Vol. 790--791, pp. 2161-2170. |
BibTeX:
@article{Nath2014,
author = {Hrusikesh Nath and Phanikumar, G},
title = {Microstructure and Phase Evolution of Ni2FeGa Heusler Alloy Extended to Different Degrees of Undercooling},
journal = {Materials Science Forum},
year = {2014},
volume = {790--791},
pages = {2161--2170},
doi = {10.4028/www.scientific.net/MSF.790-791.199}
}
|
| Prasad R, Srinivas M, Manivel Raja M and Phanikumar G (2014), "Microstructure and magnetic properties of Ni2(Mn,Fe)Ga heusler alloys rapidly solidified by melt spinning", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 45(4), pp. 2161-2170. |
| Abstract: The microstructure and magnetic properties of Ni2MnGa base alloys with "Fe" substitution in place of "Mn" are studied. The processing technique used is melt spinning at wheel speeds of 20 m/s and 30 m/s followed by annealing at 1273 K (1000 °C) for 1 hour. Fe content is varied from 2 at. pct to 11 at. pct for alloys of Ni50Mn (25-x)Fe x Ga25 with Heusler stoichiometry. Austenite with B2 partial atomic ordering and premartensitic tweed structures were found at room temperature for all the alloys at different wheel speeds. After annealing at 1273 K (1000 °C) for 1 hour, austenite phase with L2 1 Heusler atomic ordering is stabilized in samples of all the processing conditions. Saturation magnetization, martensitic transformation temperature, and Curie temperature are measured. Martensite temperature and Curie temperature increase in proportion to iron content in the alloy. Saturation magnetization is sensitive to the phase content and compositional inhomogeneities. © 2013 The Minerals, Metals & Materials Society and ASM International. |
BibTeX:
@article{Prasad2014,
author = {Prasad, R.V.S. and Srinivas, M. and Manivel Raja, M. and Phanikumar, G.},
title = {Microstructure and magnetic properties of Ni2(Mn,Fe)Ga heusler alloys rapidly solidified by melt spinning},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2014},
volume = {45},
number = {4},
pages = {2161-2170},
note = {cited By (since 1996)0},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84898826899&partnerID=40&md5=5f2a2bcdf8491b5ebdfd1ee3fe555c8a},
doi = {10.1007/s11661-013-2124-x}
}
|
| Sandhya S, Mahemaa R and Phanikumar G (2014), "Microstructure Evolution During Fusion Welding of Rheocast AA7075 Alloy", Procedia Materials Science. Vol. 5, pp. 408-415. |
BibTeX:
@article{Sandhya2014,
author = {Sandhya, S. and Mahemaa, R. and Phanikumar, G},
title = {Microstructure Evolution During Fusion Welding of Rheocast AA7075 Alloy},
journal = {Procedia Materials Science},
year = {2014},
volume = {5},
pages = {408--415},
doi = {10.1016/j.mspro.2014.07.283}
}
|
| Singh S, Chattopadhyay K, Phanikumar G and Dutta P (2014), "Experimental and numerical studies on friction welding of thixocast A356 aluminum alloy", Acta Materialia. Vol. 73, pp. 177-185. |
| Abstract: This paper highlights the role of globular microstructure on the weldability of semi-solid processed aluminum alloys via high temperature flow behavior. The investigation was carried out on the joining of thixocast A356 aluminum alloy components by friction welding. A thermomechanical model was developed to predict the temperature and stress distributions, as well as to identify the suitable and safe range of parameters. Good comparisons between numerical and experimental results were observed. In addition, metallographic examinations and hardness and tensile tests of the welded samples were carried out. It was found that the tensile strength of the joint is higher than the tensile strength of the parent material for the optimum set of parameters. © 2014 Acta Materialia Inc. |
BibTeX:
@article{Singh2014,
author = {Singh, S.K. and Chattopadhyay, K. and Phanikumar, G. and Dutta, P.},
title = {Experimental and numerical studies on friction welding of thixocast A356 aluminum alloy},
journal = {Acta Materialia},
year = {2014},
volume = {73},
pages = {177-185},
note = {cited By (since 1996)0; Article in Press},
doi = {10.1016/j.actamat.2014.04.019}
}
|
| Kala S, Prasad N and Phanikumar G (2013), "Numerical studies on effect of interpass time on distortion and residual stresses in multipass welding", Advanced Materials Research. Vol. 601, pp. 31-36. |
| Abstract: Weld distortion and residual stresses are two major issues in the fabrication process. Numerical techniques are being tried out to accurately predict the structural integrity of the welding. Interpass time in the multipass welding is an important parameter which influences the weld distortion and residual stresses. In this study two pass tungsten inert gas (TIG) welding of 6 mm mild steel plates has been analyzed using Finite element analysis (FEA) software Sysweld and parametric study is conducted with different interpass time. The temperature distribution, distortion and residual stresses are calculated using three dimensional finite element model (FEM) considering phase transformations in the material. The transient thermo-metallurgical analysis followed by elasto-plastic analysis is carried out using temperature dependent and phase dependent material properties. The material deposition in the multipass welding is numerically simulated using chewing gum method, where dummy phase and dummy material are assigned for the element activation. The phase proportions are calculated by assigning suitable phase kinetics parameter extracted from continuous cooling transformation (CCT) diagram of a given material. Experiments are conducted for validation after given edge preparation and using same material as filler wire. The FEM analysis is carried out for eight cases with different time interval between passes, starting from 30 s to 240 s in the steps of 30 s. FEM results are verified with experimentally measured values. It is found that the time interval between passes has less influence on the residual stresses but significantly affects the distortion and phase proportion due to the first pass preheating effect on second pass and second pass postheating effect on first pass. © (2013) Trans Tech Publications, Switzerland. |
BibTeX:
@article{Kala2013,
author = {Kala, S.R. and Prasad, N.S. and Phanikumar, G.},
title = {Numerical studies on effect of interpass time on distortion and residual stresses in multipass welding},
journal = {Advanced Materials Research},
year = {2013},
volume = {601},
pages = {31-36},
note = {cited By (since 1996)0},
url = {https://www.scientific.net/AMR.601.31},
doi = {10.4028/www.scientific.net/AMR.601.31}
}
|
| Khalid Rafi H, Kishore Babu N, Phanikumar G and Prasad Rao K (2013), "Microstructural evolution during friction surfacing of austenitic stainless steel AISI 304 on low carbon steel", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 44(1), pp. 345-350. |
| Abstract: Austenitic stainless steel AISI 304 coating was deposited over low carbon steel substrate by means of friction surfacing and the microstructural evolution was studied. The microstructural characterization of the coating was carried out by optical microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM). The coating exhibited refined grains (average size of 5 μm) as compared to the coarse grains (average size of 40 μm) in as-received consumable rod. The results from the microstructural characterization studies show that discontinuous dynamic recrystallization (DDRX) is the responsible mechanism for grain evolution as a consequence of severe plastic deformation. © 2012 The Minerals, Metals & Materials Society and ASM International. |
BibTeX:
@article{KhalidRafi2013,
author = {Khalid Rafi, H. and Kishore Babu, N. and Phanikumar, G. and Prasad Rao, K.},
title = {Microstructural evolution during friction surfacing of austenitic stainless steel AISI 304 on low carbon steel},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2013},
volume = {44},
number = {1},
pages = {345-350},
note = {cited By (since 1996)2},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84871990551&partnerID=40&md5=5ec8a3d37d0e018f5626b9e606b8a629},
doi = {10.1007/s11661-012-1366-3}
}
|
| Khalid Rafi H, Phanikumar G and Prasad Rao K (2013), "Corrosion resistance of friction surfaced AISI 304 stainless steel coatings", Journal of Materials Engineering and Performance. Vol. 22(2), pp. 366-370. |
| Abstract: Corrosion resistance of friction surfaced AISI 304 coating in boiling nitric acid and chloride containing environments was found to be similar to that of its consumable rod counterpart. This was in contrast to the autogenous fusion zone of GTAW weld which showed inferior corrosion resistance with respect to the consumable rod. The superior corrosion resistance of friction surfaced coatings was attributed to the absence of δ-ferrite in it. © 2012 ASM International. |
BibTeX:
@article{KhalidRafi2013a,
author = {Khalid Rafi, H. and Phanikumar, G. and Prasad Rao, K.},
title = {Corrosion resistance of friction surfaced AISI 304 stainless steel coatings},
journal = {Journal of Materials Engineering and Performance},
year = {2013},
volume = {22},
number = {2},
pages = {366-370},
note = {cited By (since 1996)1},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84876329072&partnerID=40&md5=fcddf5b2cf392bf9b8c4b42c92c140e5},
doi = {10.1007/s11665-012-0270-8}
}
|
| Sandhya S and Phanikumar G (2013), "Investigation of fusion weldments of semi-solid aluminium A356 alloy: Pool geometry and microstructure", Materials Science Forum. Vol. 765, pp. 751-755. |
| Abstract: A fusion welding technique to join a semi-solid processed A356 cast plate is explored using Gas Tungsten Arc Welding (GTAW). Semi-solid metal (SSM) billets of non-dendritic microstructure produced by rheocasting in a mould placed inside a linear electromagnetic stirrer were used for this study. GTAW experiments were conducted to simulate different thermal gradients near the fusion zone. The geometries of the weld pool as well as the temperature gradient in the fusion boundary were measured to understand the microstructure evolution. Simulation of the welding process was performed to aid in the analysis. Quantitative metallography provided the shape factor as a measure of globularity of the primary a-Al phase. Based on the studies, a model has been proposed to explain the observation of globular microstructure in the fusion zone of the welds. Conclusions show a positive correlation of thermal gradient with globular microstructure formation in this class of alloys. © (2013) Trans Tech Publications, Switzerland. |
BibTeX:
@article{Sandhya2013,
author = {Sandhya, S. and Phanikumar, G.},
title = {Investigation of fusion weldments of semi-solid aluminium A356 alloy: Pool geometry and microstructure},
journal = {Materials Science Forum},
year = {2013},
volume = {765},
pages = {751-755},
note = {cited By (since 1996)0},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84883046296&partnerID=40&md5=159267cc80310be19508678998775baf}
}
|
| Prakruthi S, Vijay Kumar K, Udupa KR, Rafi HK, Phanikumar G and Udaya Bhat K (2012), "Preparation of Al-Ni composite and its creep behavior", In Proceedings of the 3rd Asian Symposium on Materials and Processing. |
BibTeX:
@inproceedings{Prakruthi2012,
author = {Prakruthi, S and Vijay Kumar, K and Udupa, K R and Rafi, H K and Phanikumar, G and Udaya Bhat, K},
title = {Preparation of Al-Ni composite and its creep behavior},
booktitle = {Proceedings of the 3rd Asian Symposium on Materials and Processing},
year = {2012},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Prakruthi_ASMP2012.pdf}
}
|
| Prasad R, Manivel Raja M and Phanikumar G (2012), "Structure and magnetic properties of Ni 2(Mn,Co)Ga Heusler alloys rapidly solidified by melt-spinning", Intermetallics. Vol. 25, pp. 42-47. |
| Abstract: In this study microstructure and magnetic properties of cobalt substituted Ni 2MnGa based ferromagnetic shape memory alloys (FMSA) are presented. Ni 50Mn (25-x)Co xGa 25 (x = 2, 5, 8, 11 at%) alloys were synthesized using the melt-spinning technique. Martensite, austenite and pre-martensitic tweed structures were found at room temperature for alloys containing 2, 5, 8 and 11% Co and melt-spun at two extreme wheels speeds viz., 20 m/s and 30 m/s. However, the alloy containing 5% Co melt-spun at a wheel speed of 20 m/s consists of 7 M or 14 layered Martensite phase. Magnetic properties such as saturation magnetization (Ms), martensitic transformation temperature (T m) and Curie temperature (T c) were measured and were found to be attractive for most of the melt-spun alloys containing higher "Co" concentrations. Upon annealing at 1273 K for 1 h, γ (gamma) phase was found to stabilize. The magnetic properties were found to correlate with the phase content of the Co substituted alloys. © 2012 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{Prasad2012,
author = {Prasad, R.V.S. and Manivel Raja, M. and Phanikumar, G.},
title = {Structure and magnetic properties of Ni 2(Mn,Co)Ga Heusler alloys rapidly solidified by melt-spinning},
journal = {Intermetallics},
year = {2012},
volume = {25},
pages = {42-47},
note = {cited By (since 1996)0},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84858119053&partnerID=40&md5=a859d48b415bd8ceb83021c6093cea9b},
doi = {10.1016/j.intermet.2012.02.012}
}
|
| Gerald Tennyson P and Phanikumar G (2011), "Computational modelling of dendritic to globular transition using an isothermal binar phase-field model", Transactions of the Indian Institute of Metals. Vol. 64(1-2), pp. 251-254. |
BibTeX:
@article{GeraldTennyson2011,
author = {Gerald Tennyson, P. and Phanikumar, G},
title = {Computational modelling of dendritic to globular transition using an isothermal binar phase-field model},
journal = {Transactions of the Indian Institute of Metals},
year = {2011},
volume = {64},
number = {1-2},
pages = {251--254},
url = {http://www.springerlink.com/content/w4180u34170m52w4/},
doi = {10.1007/s12666-011-0050-4}
}
|
| Khalid Rafi H, Balasubramaniam K, Phanikumar G and Prasad Rao K (2011), "Thermal profiling using infrared thermography in friction surfacing", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. ??, pp. ??. |
BibTeX:
@article{KhalidRafi2011,
author = {Khalid Rafi, H. and Balasubramaniam, K. and Phanikumar, G and Prasad Rao, K.},
title = {Thermal profiling using infrared thermography in friction surfacing},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2011},
volume = {??},
pages = {??},
doi = {10.1007/s11661-011-0750-8}
}
|
| Khalid Rafi H, Phanikumar G and Prasad Rao K (2011), "Material flow visualization during friction surfacing", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 42(4), pp. 937-939. |
| Abstract: Metal flow behavior within friction surfaced coating was studied using tungsten powder as a marker. The results show that the top and bottom layers within the coating exhibit distinct flow patterns. The transport of material takes an involute path, and the material transfer starts from the advancing side of the coating to the retreating side and terminates at the center. The recirculation of material occurs at the retreating side of the coating. © 2011 The Minerals, Metals & Materials Society and ASM International. |
BibTeX:
@article{KhalidRafi2011937,
author = {Khalid Rafi, H. and Phanikumar, G. and Prasad Rao, K.},
title = {Material flow visualization during friction surfacing},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2011},
volume = {42},
number = {4},
pages = {937-939},
note = {cited By (since 1996) 0},
doi = {10.1007/s11661-011-0614-2}
}
|
| Phanikumar G, Chattopadhyay K and Dutta P (2011), "Joining of dissimilar metals: Issues and modelling techniques", Science and Technology of Welding and Joining. Vol. 16(4), pp. 313-317. |
| Abstract: Joining of dissimilar metals involves a number of scientific issues, the modelling of which offers unique challenges. This review discusses the complexities in different joining processes and dissimilar combinations, and the corresponding computational techniques that have the potential to address the same. Future directions in modelling at both macroscopic and microscopic scales are also suggested. © 2011 Institute of Materials, Minerals and Mining. |
BibTeX:
@article{Phanikumar2011313,
author = {Phanikumar, G and Chattopadhyay, K and , Dutta, P.},
title = {Joining of dissimilar metals: Issues and modelling techniques},
journal = {Science and Technology of Welding and Joining},
year = {2011},
volume = {16},
number = {4},
pages = {313-317},
note = {cited By (since 1996) 1},
url = {http://openurl.ingenta.com/content?genre=article&issn=1362-1718&volume=16&issue=4&spage=313&epage=317},
doi = {10.1179/1362171811Y.0000000014}
}
|
| Prasad R and Phanikumar G (2011), "Phase evolution and properties of Ni50Co23Fe2Ga25 Heusler alloy undercooled by electromagnetic levitation", Intermetallics. Vol. 19, pp. 1705-1710. |
BibTeX:
@article{Prasad2011,
author = {Prasad, R.V.S. and Phanikumar, G},
title = {Phase evolution and properties of Ni50Co23Fe2Ga25 Heusler alloy undercooled by electromagnetic levitation},
journal = {Intermetallics},
year = {2011},
volume = {19},
pages = {1705--1710},
doi = {10.1016/j.intermet.2011.07.009}
}
|
| Rafi H, Ram G, Phanikumar G and Rao K (2011), "Microstructural evolution during friction surfacing of tool steel H13", Materials and Design. Vol. 32(1), pp. 82-87. |
| Abstract: Coatings of AISI H13 tool steel were made on low carbon steel by friction surfacing. Detailed microstructural studies and microhardness tests were carried out on the coatings. Studies revealed defect-free coatings and sound metallurgical bonding between the coating and the substrate. In addition, mechanical interlocking on a very fine scale was observed to occur between the coating and the substrate. Coatings exhibited martensitic microstructure with fine grain size and with no carbide particles. Coatings in as-deposited condition showed very high hardness (58 HRC) compared to the mechtrode material in annealed condition (20 HRC). Based on these findings, microstructural evolution during friction surfacing of H13 tool steel is discussed. The current work shows that friction surfaced tool steel coatings are suitable for use in as-deposited condition. Further improvements in coating microstructure and properties are possible with appropriate post-surfacing heat treatment. © 2010 Elsevier Ltd. |
BibTeX:
@article{Rafi201182,
author = {Rafi, H.K. and Ram, G.D.J. and Phanikumar, G. and Rao, K.P.},
title = {Microstructural evolution during friction surfacing of tool steel H13},
journal = {Materials and Design},
year = {2011},
volume = {32},
number = {1},
pages = {82-87},
note = {cited By (since 1996) 0},
doi = {10.1016/j.matdes.2010.06.031}
}
|
| Ravi K, Manivannan S, Phanikumar G, Murty B and Sundarraj S (2011), "Influence of Mg on Grain Refinement of Near Eutectic Al-Si Alloys", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 42(7), pp. 2028-2039. |
| Abstract: Although the grain-refinement practice is well established for wrought Al alloys, in the case of foundry alloys such as near eutectic Al-Si alloys, the underlying mechanisms and the use of grain refiners need better understanding. Conventional grain refiners such as Al-5Ti-1B are not effective in grain refining the Al-Si alloys due to the poisoning effect of Si. In this work, we report the results of a newly developed grain refiner, which can effectively grain refine as well as modify eutectic and primary Si in near eutectic Al-Si alloys. Among the material choices, the grain refining response with Al-1Ti-3B master alloy is found to be superior compared to the conventional Al-5Ti-1B master alloy. It was also found that magnesium additions of 0.2 wt pct along with the Al-1Ti-3B master alloy further enhance the near eutectic Al-Si alloy's grain refining efficiency, thus leading to improved bulk mechanical properties. We have found that magnesium essentially scavenges the oxygen present on the surface of nucleant particles, improves wettability, and reduces the agglomeration tendency of boride particles, thereby enhancing grain refining efficiency. It allows the nucleant particles to act as potent and active nucleation sites even at levels as low as 0.2 pct in the Al-1Ti-3B master alloy. © 2011 The Minerals, Metals & Materials Society and ASM International. |
BibTeX:
@article{Ravi2011,
author = {Ravi, K.R. and Manivannan, S. and Phanikumar, G. and Murty, B.S. and Sundarraj, S.},
title = {Influence of Mg on Grain Refinement of Near Eutectic Al-Si Alloys},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2011},
volume = {42},
number = {7},
pages = {2028--2039},
note = {cited By (since 1996) 0; Article in Press},
doi = {10.1007/s11661-010-0600-0}
}
|
| Srinivas M, Majumdar B, Phanikumar G and Akhtar D (2011), "Effect of planar flow melt spinning parameters on ribbon formation in soft magnetic Fe68.5Si18.5B9Nb3Cu 1 alloy", Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science. Vol. 42(2), pp. 370-379. |
| Abstract: The effect of planar flow melt spinning (PFMS) parameters on the continuity, surface quality, and structure of 10-mm-wide Fe 68.5Si18.5B9Nb3Cu1 ribbons has been investigated. The change in shape and stability of the melt puddle as a function of the processing parameter was studied using a high-speed imaging system and was correlated to ribbon formation. A window of process parameters for obtaining continuous ribbons with good surface quality has been evaluated. It has been observed that thinner ribbons are found to be more continuous because of higher ductility. The higher melt temperature leads to the formation of crystalline phase in as-spun ribbons, and this deteriorates the soft magnetic properties on annealing. The experimental results are corroborated with the numerical estimates, which suggest that the critical thickness for amorphous phase formation decreases with increasing initial melt temperature. © The Minerals, Metals & Materials Society and ASM International 2011. |
BibTeX:
@article{Srinivas2011370,
author = {Srinivas, M. and Majumdar, B. and Phanikumar, G. and Akhtar, D.},
title = {Effect of planar flow melt spinning parameters on ribbon formation in soft magnetic Fe68.5Si18.5B9Nb3Cu 1 alloy},
journal = {Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science},
year = {2011},
volume = {42},
number = {2},
pages = {370-379},
note = {cited By (since 1996) 0},
doi = {10.1007/s11663-011-9476-7}
}
|
| Gerald Tennyson P, Kumar P, Lakshmi H, Phanikumar G and Dutta P (2010), "Experimental studies and phase field modeling of microstructure evolution during solidification with electromagnetic stirring", Transactions of Nonferrous Metals Society of China (English Edition). Vol. 20(SUPPL. 3), pp. s774-s780. |
| Abstract: Thixocasting requires manufacturing of billets with non-dendritic microstructure. Aluminum alloy A356 billets were produced by rheocasting in a mould placed inside a linear electromagnetic stirrer. Subsequent heat treatment was used to produce a transition from rosette to globular microstructure. The current and the duration of stirring were explored as control parameters. Simultaneous induction heating of the billet during stirring was quantified using experimentally determined thermal profiles. The effect of processing parameters on the dendrite fragmentation was discussed. Corresponding computational modeling of the process was performed using phase-field modeling of alloy solidification in order to gain insight into the process of morphological changes of a solid during this process. A non-isothermal alloy solidification model was used for simulations. The morphological evolution under such imposed thermal cycles was simulated and compared with experimentally determined one. Suitable scaling using the thermosolutal diffusion distances was used to overcome computational difficulties in quantitative comparison at system scale. The results were interpreted in the light of existing theories of microstructure refinement and globularisation. © 2010 The Nonferrous Metals Society of China. |
BibTeX:
@article{GeraldTennyson2010,
author = {Gerald Tennyson, P. and Kumar, P. and Lakshmi, H. and Phanikumar, G and Dutta, P.},
title = {Experimental studies and phase field modeling of microstructure evolution during solidification with electromagnetic stirring},
journal = {Transactions of Nonferrous Metals Society of China (English Edition)},
year = {2010},
volume = {20},
number = {SUPPL. 3},
pages = {s774-s780},
note = {cited By (since 1996) 0},
doi = {10.1016/S1003-6326(10)60580-8}
}
|
| Khalid Rafi H, Janaki Ram G, Phanikumar G and Prasad Rao K (2010), "Friction surfacing of austenitic stainless steel on low carbon steel: Studies on the effects of traverse speed", In World Congress on Engineering. Vol. 2, pp. 1356-1360. |
| Abstract: This work deals with the solid state coatings by friction surfacing process. AISI 310 austenitic stainless steel is coated on low carbon steel substrate. The effects of traverse speed on the geometry, interfacial bond characteristics and mechanical properties of coatings are studied. Traverse speed was varied and rotational speed and axial load were fixed. Metallurgical studies were made using optical microscopy, scanning electron microscopy (SEM), mechanical tests included shear tests, bend tests and microhardness tests. The coatings are free from cracks and have a fully austenitic structure. Traverse speed influenced both bond integrity and coating thickness. Metallurgically sound interface with 100% bond integrity was found for coatings made with higher traverse speeds. Higher the traverse speed thinner the coating and higher the bond strength. |
BibTeX:
@conference{KhalidRafi2010,
author = {Khalid Rafi, H. and Janaki Ram, G. and Phanikumar, G and Prasad Rao, K.},
title = {Friction surfacing of austenitic stainless steel on low carbon steel: Studies on the effects of traverse speed},
booktitle = {World Congress on Engineering},
year = {2010},
volume = {2},
pages = {1356-1360},
note = {978-988182107-2},
url = {https://mme.iitm.ac.in/gphani/assets/publications/KhalidRafi_WCE2010.pdf}
}
|
| Khalid Rafi H, Janaki Ram G, Phanikumar G and Prasad Rao K (2010), "Microstructure and properties of friction surfaced stainless steel and tool steel coatings", Materials Science Forum. Vol. 638-642, pp. 864-869. |
| Abstract: Friction surfacing is a novel solid state surface coating process with several advantages over conventional fusion welding based surfacing processes. In this work, austenitic stainless steel (AISI 310) and tool steel (H13) coatings were friction deposited on mild steel substrates for corrosion and wear protection, respectively. Microstructural studies were carried out by using optical and scanning electron microscopy. Shear tests and bend tests (ASTM A264) were conducted to assess the integrity of the coatings. This study brings out the microstructural features across the coating/substrate interface and its mechanical properties, showing good metallurgical bonding between stainless steel and tool steel coating over mild steel. © (2010) Trans Tech Publications. |
BibTeX:
@article{KhalidRafi2010864,
author = {Khalid Rafi, H. and Janaki Ram, G.D. and Phanikumar, G. and Prasad Rao, K.},
title = {Microstructure and properties of friction surfaced stainless steel and tool steel coatings},
journal = {Materials Science Forum},
year = {2010},
volume = {638-642},
pages = {864-869},
note = {cited By (since 1996) 0},
doi = {10.4028/www.scientific.net/MSF.638-642.864}
}
|
| Nair B, Rakesh S, Phanikumar G, Rao K and Sinha P (2010), "Fracture toughness (J1C) of electron beam welded AA2219 alloy", Materials and Design. Vol. 31(10), pp. 4943-4950. |
| Abstract: AA2219 (Al-6%Cu) was butt welded in T87 temper (solution heat-treated, cold worked and precipitation hardened) and T6 temper (solution heat-treated and precipitation hardened) using electron beam welding (EBW). Variables studied were base metal temper condition and mode of EBW. Mechanical properties of the weld joint and fracture toughness at fusion zone (FZ) and heat-affected zone (HAZ) were evaluated and compared with those of the base metal. Results showed that EB welds have higher joint efficiency and fracture toughness than that of gas tungsten arc welding (GTAW). Fracture toughness of T6 base metal was found to be higher than its T87 counterpart. When welded, FZ and HAZ in T87 showed higher fracture toughness than that of T6; HAZ was the toughest. Pulsed current (PC) EB weld showed marginal reduction in toughness compared to constant current (CC) weld. Toughness variation is analyzed with the help of tensile test, Charpy impact test and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). © 2010 Elsevier Ltd. |
BibTeX:
@article{Nair20104943,
author = {Nair, B.S. and Rakesh, S. and Phanikumar, G. and Rao, K.P. and Sinha, P.P.},
title = {Fracture toughness (J1C) of electron beam welded AA2219 alloy},
journal = {Materials and Design},
year = {2010},
volume = {31},
number = {10},
pages = {4943-4950},
note = {cited By (since 1996) 0},
doi = {10.1016/j.matdes.2010.05.017}
}
|
| Prasad R and Phanikumar G (2010), "Martensite and nanocrystalline phase formation in rapidly solidified Ni2MnGa alloy by melt-spinning", Materials Science Forum. Vol. 649, pp. 35-40. |
| Abstract: Microstructure of rapidly solidified Ni2MnGa ferromagnetic shape memory alloy has been investigated experimentally by melt-spinning technique. At a constant ribbon width of 3 mm, two speeds of melt spinning 17m/sec and 30m/sec at the extrema of conditions for a good quality of ribbon resulted in two thicknesses of the ribbon, viz., 62 μm and 44 μm, respectively. TEM and AFM analysis reveals the formation of very fine clusters of Ni 2MnGa at lower wheel speeds. However at higher wheel speeds nanocrystalline Ni2MnGa particles of size about 10-20 nm and martensitic phases were confirmed. © (2010) Trans Tech Publications. |
BibTeX:
@article{Prasad201035,
author = {Prasad, R.V.S. and Phanikumar, G.},
title = {Martensite and nanocrystalline phase formation in rapidly solidified Ni2MnGa alloy by melt-spinning},
journal = {Materials Science Forum},
year = {2010},
volume = {649},
pages = {35-40},
note = {cited By (since 1996) 0},
doi = {10.4028/www.scientific.net/MSF.649.35}
}
|
| Rafi H, Ram G, Phanikumar G and Rao K (2010), "Microstructure and tensile properties of friction welded aluminum alloy AA7075-T6", Materials and Design. Vol. 31(5), pp. 2375-2380. |
| Abstract: Solid-state welding processes like friction welding and friction stir welding are now being actively considered for welding aluminum alloy AA7075. In this work, friction welding of AA7075-T6 rods of 13 mm diameter was investigated with an aim to understand the effects of process parameters on weld microstructure and tensile properties. Welds made with various process parameter combinations (incorporating Taguchi methods) were subjected to tensile tests. Microstructural studies and hardness tests were also conducted. The results show that sound joints in AA7075-T6 can be achieved using friction welding, with a joint efficiency of 89% in as-welded condition with careful selection of process parameters. The effects of process parameters are discussed in detail based on microstructural observations. © 2009 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{Rafi2010,
author = {Rafi, H.K. and Ram, G.D.J. and Phanikumar, G. and Rao, K.P.},
title = {Microstructure and tensile properties of friction welded aluminum alloy AA7075-T6},
journal = {Materials and Design},
year = {2010},
volume = {31},
number = {5},
pages = {2375-2380},
note = {cited By (since 1996) 3},
doi = {10.1016/j.matdes.2009.11.065}
}
|
| Rafi H, Ram G, Phanikumar G and Rao K (2010), "Friction surfaced tool steel (H13) coatings on low carbon steel: A study on the effects of process parameters on coating characteristics and integrity", Surface and Coatings Technology. Vol. 205(1), pp. 232-242. |
| Abstract: Tool steel H13 was friction surfaced on low carbon steel substrates. Mechtrode (consumable rod) rotational speed and substrate traverse speed were varied, keeping the axial force constant. The effects of process parameters on coating characteristics and integrity were evaluated. A process parameter window was developed for satisfactory deposition of tool steel coatings. Coating microstructures were examined using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microhardness tests, shear tests, and bend tests were conducted on coatings. The results show that coating width is a strong function of mechtrode rotational speed, while coating thickness is mainly dependent on substrate traverse speed. Lower mechtrode rotational speeds results in wider coatings, while higher substrate traverse speeds produce thinner coatings. Thinner coatings exhibit higher bond strength than thicker coatings. Coatings show no carbide particles, yet exhibit excellent hardness (above 600 HV) in as-deposited condition due to their martensitic microstructure. © 2010 Elsevier B.V. |
BibTeX:
@article{Rafi2010232,
author = {Rafi, H.K. and Ram, G.D.J. and Phanikumar, G. and Rao, K.P.},
title = {Friction surfaced tool steel (H13) coatings on low carbon steel: A study on the effects of process parameters on coating characteristics and integrity},
journal = {Surface and Coatings Technology},
year = {2010},
volume = {205},
number = {1},
pages = {232-242},
note = {cited By (since 1996) 0},
doi = {10.1016/j.surfcoat.2010.06.052}
}
|
| Balachandar K, Subramanya Sarma V, Pant B and Phanikumar G (2009), "Microstructure and Mechanical Properties of Gas-Tungsten-Arc-Welded Ti-15-3 Beta Titanium Alloy", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 40, pp. 2685-2693. |
| Abstract: Microstructure and mechanical properties of gas-tungsten-arc (GTA)-welded Ti-15V-3Cr-3Sn-3Al alloy in direct current electrode negative mode are characterized. The thermal profile was measured during welding with continuous current (CC) and pulsed current (PC) at different frequencies. A single-step postweld aging of the welded samples at subtransus temperature was attempted to study precipitation of alpha phase. Two different morphologies of alpha phase are observed along with a partitioning of alloying elements into the two phases. Processing conditions for higher strength are identified and correlated with the thermal profile. Microstructure changes due to postweld heat treatment were characterized. © 2009 The Minerals, Metals & Materials Society and ASM International. |
BibTeX:
@article{Balachandar2009,
author = {Balachandar, K. and Subramanya Sarma, V. and , Pant, B. and Phanikumar, G.},
title = {Microstructure and Mechanical Properties of Gas-Tungsten-Arc-Welded Ti-15-3 Beta Titanium Alloy},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2009},
volume = {40},
pages = {2685-2693},
note = {cited By (since 1996) 0; Article in Press},
doi = {10.1007/s11661-009-9952-8}
}
|
| Prasad R, Manivel Raja M and Phanikumar G (2009), "Microstructure and magnetic properties of rapidly solidified Ni 2(Mn,Fe)Ga Heusler alloys", Advanced Materials Research. Vol. 74, pp. 215-218. |
| Abstract: This study reports detailed microstructural and magnetic characterization of rapidly solidified Ni2(Mn,Fe)Ga heusler alloys processed using the melt spinning technique. Series of Ni50Mn(25-x)Fe( x= 2, 5, 8, 11)Ga25 alloys were prepared by vacuum arc melting and then melt spun at constant wheel speed of 20 m/sec to obtain samples in the form of ribbons. X-ray diffraction analysis of as-cast Ni 2(Mn,Fe)Ga alloy with different 'Fe' concentrations revealed austenite phase with L21 Heusler atomic order at room temperature. Transmission electron microscopy of melt spun ribbons reveals a precursor tweed structures due to magnetic tweed contrast when the 'Fe' concentrations are 8% and 11%. In case of 11% 'Fe' substituted alloy martensite phase was found to from at the grain boundary triple junctions. Thermo magnetic measurements determine that, as the 'Fe' concentration increases from 2 to 11%; it enhances the magnetic transition temperature from 375 to 403 K. © (2009) Trans Tech Publications. |
BibTeX:
@article{Prasad2009215,
author = {Prasad, R.V.S. and Manivel Raja, M. and Phanikumar, G.},
title = {Microstructure and magnetic properties of rapidly solidified Ni 2(Mn,Fe)Ga Heusler alloys},
journal = {Advanced Materials Research},
year = {2009},
volume = {74},
pages = {215-218},
note = {cited By (since 1996) 0},
doi = {10.4028/www.scientific.net/AMR.74.215}
}
|
| Prasad R and Phanikumar G (2009), "Amorphous and nano crystalline phase formation in Ni2MnGa ferromagnetic shape memory alloy synthesized by melt spinning", Journal of Materials Science. Vol. 44(10), pp. 2553-2559. |
| Abstract: Melt spinning technique was used to synthesize Ni2MnGa ferromagnetic shape memory alloy ribbons. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis of the ribbon synthesized at lower wheel speed (20 m/s) reveal the formation of very fine clusters of austenitic phase of Ni2MnGa. However at higher wheel speed (30 m/s) the formation of martensite and nanoparticles of Ni2MnGa with a size range of 10-20 nm in the amorphous matrix is observed. Also an amorphous phase was observed at higher wheel speed in some areas of the ribbon. Annealing (1000 °C, 1 h) of the ribbon synthesized at higher wheel speed resulted in martensite and γ (gamma) phases. Amorphous phase, Ni2MnGa nanoparticles, and the martensite phase are analyzed in detail. © 2009 Springer Science+Business Media, LLC. |
BibTeX:
@article{Prasad20092553,
author = {Prasad, R.V.S. and Phanikumar, G.},
title = {Amorphous and nano crystalline phase formation in Ni2MnGa ferromagnetic shape memory alloy synthesized by melt spinning},
journal = {Journal of Materials Science},
year = {2009},
volume = {44},
number = {10},
pages = {2553-2559},
note = {cited By (since 1996) 4},
doi = {10.1007/s10853-009-3333-y}
}
|
| Sreenivas Rao K, Arun Kumar S, Phanikumar G and Prasanna Kumar T (2008), "Effect of boundary heat flux transients on the solidification behavior and microstructure of AL-CU alloy", TMS Annual Meeting., In Extraction and Processing Division - EPD Congress 2008 - Held during TMS 2008 Annual Meeting and Exhibition., March, 2008. , pp. 271-280. TMS. |
| Abstract: Solidification experiments have been conducted to study the effect of interface heat flux and air gap formation on cooling rate of the casting during solidification of Al-4.5wt%Cu alloy. The thermal history of the casting and mold during solidification is recorded using thermocouples connected to computer interfaced data logger. The measured temperatures in the mold are used as input to the IHCP (inverse heat conduction problem) algorithm for simulating multiple heat flux components at the boundary. It is observed that the filling effects induce spatial variation in the thermal field in the mold and casting regions and greatly influence the cooling rate of the casting. The study demonstrates the use of IHCP and in-situ measured thermal profile in analyzing the cooling rate and microstructure. |
BibTeX:
@conference{SreenivasRao2008271,
author = {Sreenivas Rao, K.V. and Arun Kumar, S. and Phanikumar, G. and Prasanna Kumar, T.S.},
title = {Effect of boundary heat flux transients on the solidification behavior and microstructure of AL-CU alloy},
booktitle = {Extraction and Processing Division - EPD Congress 2008 - Held during TMS 2008 Annual Meeting and Exhibition},
journal = {TMS Annual Meeting},
publisher = {TMS},
year = {2008},
pages = {271-280},
note = {ISBN: 978-087339715-5},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-52649180574&partnerID=40&md5=3ad99d37623c371af2ce21b29fc711c8}
}
|
| Biswas K, Phanikumar G, Herlach D and Chattopadhyay K (2007), "Non-equilibrium solidification of concentrated Fe-Ge alloys", Materials Science and Engineering A. Vol. 448-451, pp. 12-17. |
| Abstract: The solidification of concentrated alloys containing ordered compounds is less well understood. These alloys often exhibit complex phase change like peritectic reaction during liquid to solid transformation. The Fe-rich part of Fe-Ge binary alloy system consists of several critical points and ordered-disorder transitions and can be used as a model system to study the effect of departure from equilibrium on the solidification microstructure. In order to understand the phase selection and morphological transitions, undercooling and recalescence behaviour; growth rate of the solidifying phases and microstructure need to be explored. In the present paper, we summarise the results obtained in several iron rich alloy compositions (Fe-(14-25) at.br> Ge) using techniques of melt quenching, levitation and laser resolidification. These results provide insight to the current theories of dendritic growth and reveals possibility of a new pathway for phase evolution in peritectic alloys at high undercooling involving a massive transformation. © 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Biswas200712,
author = {Biswas, K. and Phanikumar, G. and Herlach, D.M. and Chattopadhyay, K.},
title = {Non-equilibrium solidification of concentrated Fe-Ge alloys},
journal = {Materials Science and Engineering A},
year = {2007},
volume = {448-451},
pages = {12-17},
note = {cited By (since 1996) 4},
doi = {10.1016/j.msea.2006.02.286}
}
|
| Biswas K, Phanikumar G, Holland-Moritz D, Herlach D and Chattopadhyay K (2007), "Disorder trapping and grain refinement during solidification of undercooled Fe-18 at% Ge melts", Philosophical Magazine. Vol. 87(25), pp. 3817-3837. |
| Abstract: The electromagnetic levitation technique has been used to systematically study microstructure evolution and growth rate as a function of undercooling in concentrated Fe-18 at% Ge alloy. The samples are undercooled to a maximum of 240 K. Growth-rate analysis and transmission electron microscopy reveal that, beyond an undercooling of 120 K, the primary phase to solidify is disordered. Microstructural investigations show a decrease in grain size with increasing undercooling. Orientation-imaging microscopy using electron back-scattered diffraction (EBSD) and microhardness measurements have been used to show that recovery and recrystallization play a significant role in the evolution of final microstructure. Microstructural evolution has also been discussed in light of current models of dendrite growth and grain refinement. |
BibTeX:
@article{Biswas20073817,
author = {Biswas, K. and Phanikumar, G. and Holland-Moritz, D and Herlach, D.M. and Chattopadhyay, K.},
title = {Disorder trapping and grain refinement during solidification of undercooled Fe-18 at% Ge melts},
journal = {Philosophical Magazine},
year = {2007},
volume = {87},
number = {25},
pages = {3817-3837},
note = {cited By (since 1996) 1},
doi = {10.1080/14786430701420549}
}
|
| Galenko P, Phanikumar G, Funke O, Chernova L, Reutzel S, Kolbe M and Herlach D (2007), "Dendritic solidification and fragmentation in undercooled Ni-Zr alloys", Materials Science and Engineering A. Vol. 448-451, pp. 649-653. |
| Abstract: Kinetics of dendritic solidification and fragmentation of dendritic crystals in undercooled Ni-Zr samples are studied. Using the capacitance proximity sensor technique and a high-speed-camera system, the dendrite growth velocity has been measured as a function of initial undercooling in solidifying droplets processed by the electromagnetic levitation technique. Analyses of solidified droplets give evidence to a transition from coarse grained dendrites to grain refined dendrites (CG-GR) at small undercooling, a transition from grain refined dendrites to coarse grained dendrites (GR-CG) at moderate undercooling, and to a second transition from coarse grained dendrites to grain refined dendrites (CG-GR) at a higher undercooling. Predictions of a sharp-interface model are compared with the results of experiments on Ni-Zr samples. © 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Galenko2007649,
author = {Galenko, P.K. and Phanikumar, G. and Funke, O. and Chernova, L. and Reutzel, S. and Kolbe, M. and Herlach, D.M.},
title = {Dendritic solidification and fragmentation in undercooled Ni-Zr alloys},
journal = {Materials Science and Engineering A},
year = {2007},
volume = {448-451},
pages = {649-653},
note = {cited By (since 1996) 4},
doi = {10.1016/j.msea.2006.02.435}
}
|
| Gupta A, Galun R and Phanikumar G (2007), "Microstructure evolution during laser surface cladding and remelting of Al-10wt%Bi-10wt%Cu", Transactions of the Indian Institute of Metals. Vol. 60(2-3), pp. 299-302. |
| Abstract: Laser surface cladding and remelting provides a route to synthesize functional microstructures on the surface of structurally important materials. Alloys containing fine soft particles embedded uniformly in a hard matrix find applications as bearing materials with low friction coefficient. Elemental powder mixtures are used to clad Al + 10wt%Cu + 10wt%Bi on the surface of aluminium base metal in both single and multi-track mode at two different cladding speeds. The clad layers are remelted at speeds varying from 500 mm/min to 2500 mm/min to simulate different solidification speeds. Microstructure evolution during the process is studied by measuring particle size distribution and alignment to identify optimum processing conditions. Pin on disc experiments show a low friction coefficient of 0.22 for the samples remelted at 2500 mm/min. |
BibTeX:
@article{Gupta2007299,
author = {Gupta, A.K. and Galun, R. and Phanikumar, G.},
title = {Microstructure evolution during laser surface cladding and remelting of Al-10wt%Bi-10wt%Cu},
journal = {Transactions of the Indian Institute of Metals},
year = {2007},
volume = {60},
number = {2-3},
pages = {299-302},
note = {cited By (since 1996) 0},
url = {http://www.igcar.ernet.in/transiim/2007/vol60-2and3.pdf}
}
|
| Lierfeld T, Gandham P, Kolbe M, Schenk T, Singer H, Eggeler G and Herlach D (2007), "Particle incorporation in metallic melts during dendritic solidification-undercooling experiments under reduced gravity", Materials Science and Engineering A. Vol. 448-451, pp. 689-692. |
| Abstract: The interaction of ceramic particles with a dendritic solid/liquid-interface has been investigated by undercooling experiments with different levels of convection: (i) in a terrestrial electromagnetic levitation facility and (ii) in TEMPUS, a facility for containerless processing, under low gravity conditions during parabolic flights. Entrapment of particles in ground experiments and engulfment of a significant fraction of submicron particles under low gravity conditions are attributed to the lower level of convection in the latter experiments and to morphological features of dendritic solidification. X-ray radiography has been used for in situ observations of directional solidification in Al90Cu10 with alumina particles. © 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Lierfeld2007689,
author = {Lierfeld, T. and Gandham, P. and Kolbe, M. and Schenk, T. and Singer, H.M. and Eggeler, G. and Herlach, D.M.},
title = {Particle incorporation in metallic melts during dendritic solidification-undercooling experiments under reduced gravity},
journal = {Materials Science and Engineering A},
year = {2007},
volume = {448-451},
pages = {689-692},
note = {cited By (since 1996) 1},
doi = {10.1016/j.msea.2006.02.453}
}
|
| Nair B, Phanikumar G, Prasad Rao K and Sinha P (2007), "Improvement of mechanical properties of gas tungsten arc and electron beam welded AA2219 (Al-6 wt-%Cu) alloy", Science and Technology of Welding and Joining. Vol. 12(7), pp. 579-585. |
| Abstract: Despite its excellent weldability characteristics, AA2219 suffers from poor fusion zone strength under the as welded condition. In the present work, it is attempted to increase the mechanical properties of the as welded fusion zone of this alloy by increasing the weld cooling rates and multipass welding. The cooling rate was increased with the use of high intense heat source, namely electron beam in a pulsed current mode. Multipass gas tungsten arc welding was carried out using direct current straight polarity. These techniques resulted in a significant improvement in fusion zone hardness and tensile properties, which is attributed to reduced copper segregation and natural aging as well as aging caused by heat of multipass welding. © 2007 Institute of Materials, Minerals and Mining. |
BibTeX:
@article{Nair2007579,
author = {Nair, B.S. and Phanikumar, G. and Prasad Rao, K. and Sinha, P.P.},
title = {Improvement of mechanical properties of gas tungsten arc and electron beam welded AA2219 (Al-6 wt-%Cu) alloy},
journal = {Science and Technology of Welding and Joining},
year = {2007},
volume = {12},
number = {7},
pages = {579-585},
note = {cited By (since 1996) 5},
url = {http://openurl.ingenta.com/content?genre=article&issn=1362-1718&volume=12&issue=7&spage=579&epage=585},
doi = {10.1179/174329307X227210}
}
|
| Funke O, Phanikumar G, Galenko P, Chernova L, Reutzel S, Kolbe M and Herlach D (2006), "Dendrite growth velocity in levitated undercooled nickel melts", Journal of Crystal Growth. Vol. 297(1), pp. 211-222. |
| Abstract: Model predictions for the dendrite growth velocity at low undercoolings are deviating significantly from experimental data obtained in electromagnetic levitation with a capacitance proximity sensor (CPS) [K. Eckler, D.M. Herlach, Mater. Sci. Eng. A 178 (1994) 159]. In addition to that, previous data sets obtained by different techniques are not in good agreement with each other. For instance, growth velocity data for nickel melts obtained with a high-speed camera system [D.M. Matson, in: Solidification 1998, TMS, Warrendale PA, 1998, p. 233] show higher values at low undercoolings than data obtained with the CPS. Within this work new measurements of dendritic growth velocity in levitated undercooled nickel samples were performed as a function of undercooling ΔT to investigate this discrepancy. Solidification of the undercooled melt was detected at undercooling levels within the range of 30 K<ΔT<300 K. The new data reveal high accuracy and low scattering. These data are compared with two independent growth velocity data sets and discrepancies are discussed. For verification of the new CPS data dendrite growth velocity was also measured by using a high-speed camera where the morphology of the intersection of the solidification front with the sample surface was investigated. The new experimental data are analyzed within the model of dendrite growth obtained on the basis of Brener's theory [E. Brener, J. Crystal Growth 99 (1990) 165] and the model of dendrite growth with melt convection in a solidifying levitated drop, presently being developed. Special attention is paid to the effects of convection and small amounts of impurities on the growth dynamics at small undercoolings. © 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Funke2006211,
author = {Funke, O. and Phanikumar, G. and Galenko, P.K. and Chernova, L. and Reutzel, S. and Kolbe, M. and Herlach, D.M.},
title = {Dendrite growth velocity in levitated undercooled nickel melts},
journal = {Journal of Crystal Growth},
year = {2006},
volume = {297},
number = {1},
pages = {211-222},
note = {cited By (since 1996) 10},
doi = {10.1016/j.jcrysgro.2006.08.045}
}
|
| Galenko P, Herlach D, Phanikumar G and Funke O (2006), "Phase-field modeling of dendritic solidification in undercooled droplets processed by electromagnetic levitation", Materials Science Forum. Vol. 508, pp. 431-436. |
| Abstract: The results on modeling dendritic solidification from undercooled melts processed by the electromagnetic levitation technique are discussed. In order to model the details of formation of dendritic patterns we use a phase-field model of dendritic growth in a pure undercooled system with convection of the liquid phase. The predictions of the phase-field model are discussed referring to our latest high accuracy measurements of dendrite growth velocities in nickel samples. Special emphasis is given to the growth of dendrites at small and moderate undercoolings. At small undercoolings, the theoretical predictions deviate systematically from experimental data for solidification of nickel dendrites. It is shown that small amounts of impurities and forced convective flow can lead to an enhancement of the velocity of dendritic solidification at small undercoolings. |
BibTeX:
@article{Galenko2006431,
author = {Galenko, P.K. and Herlach, D.M. and Phanikumar, G. and Funke, O.},
title = {Phase-field modeling of dendritic solidification in undercooled droplets processed by electromagnetic levitation},
journal = {Materials Science Forum},
year = {2006},
volume = {508},
pages = {431-436},
note = {cited By (since 1996) 2},
doi = {10.4028/www.scientific.net/MSF.508.431}
}
|
| Phanikumar G, Dutta P and Chattopadhyay K (2005), "Continuous welding of Cu-Ni dissimilar couple using CO2 laser", Science and Technology of Welding and Joining. Vol. 10(2), pp. 158-166. |
| Abstract: The evolution of microstructure during continuous laser welding of dissimilar metals has been studied for a binary Cu-Ni couple. The effects of laser beam scan speed and laser power on the shape and size of the melt pool, the weldment-substrate interface, the composition profiles, and microstructures of the weldments have been investigated. It is shown that the melt pools exhibit a characteristic asymmetry In shape. The observed microstructure is characterised by the existence of compositional and microstructural variations leading to a banded appearance suggesting localised mixing. Distinct differences exist In the evolution of the microstructure in the copper and nickel sides of the weld pool. An attempt Is made to explain some of the experimental observations using thermodynamic and thermal transport arguments. © 2005 Institute of Materials, Minerals and Mining. |
BibTeX:
@article{Phanikumar2005158,
author = {Phanikumar, G. and Dutta, P. and Chattopadhyay, K.},
title = {Continuous welding of Cu-Ni dissimilar couple using CO2 laser},
journal = {Science and Technology of Welding and Joining},
year = {2005},
volume = {10},
number = {2},
pages = {158-166},
note = {cited By (since 1996) 6},
url = {http://openurl.ingenta.com/content?genre=article&issn=1362-1718&volume=10&issue=2&spage=158&epage=166},
doi = {10.1179/174329305X36043}
}
|
| Phanikumar G, Manjini S, Dutta P, Mazumder J and Chattopadhyay K (2005), "Characterization of a continuous CO2 laser-welded Fe-Cu dissimilar couple", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 36(8), pp. 2137-2147. |
| Abstract: Continuous CO2 laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process conditions are varied to identify and characterize the microstructural features that are independent of the welding mode. The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural analysis of the weld/ base-metal interface shows features that are different on the two sides of the weld. The iron side can grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth. The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis of the Fe-Cu system. |
BibTeX:
@article{Phanikumar20052137,
author = {Phanikumar, G. and Manjini, S. and Dutta, P. and Mazumder, J. and Chattopadhyay, K.},
title = {Characterization of a continuous CO2 laser-welded Fe-Cu dissimilar couple},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2005},
volume = {36},
number = {8},
pages = {2137-2147},
note = {cited By (since 1996) 9},
doi = {10.1007/s11661-005-0334-6}
}
|
| Phanikumar G, Biswas K, Funke O, Holland-Moritz D, Herlach D and Chattopadhyay K (2005), "Solidification of undercooled peritectic Fe-Ge alloy", Acta Materialia. Vol. 53(13), pp. 3591-3600. |
| Abstract: Bulk samples of Fe-25 at.% Ge peritectic alloy are undercooled up to 260 K using electromagnetic levitation technique. The growth rate of the primary phase is measured using a capacitance proximity sensor technique. Solidification microstructure is studied as a function of undercooling. The microstructure of samples at low undercoolings consists of a residual primary phase α2, peritectic phase ε and inter-dendritic ε-β eutectic. Microstructure at higher undercoolings is nearly phase-pure ε. Time resolved diffraction analysis of the levitated droplets using synchrotron radiation indicates the nucleation of primary α2 in all cases. The growth rate is analysed using current theories to explain the experimental observations. Interfacial undercooling is found to play an important role in the growth kinetics. Our results also suggest suppression of peritectic reaction. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. |
BibTeX:
@article{Phanikumar20053591,
author = {Phanikumar, G. and Biswas, K. and Funke, O. and Holland-Moritz, D. and Herlach, D.M. and Chattopadhyay, K.},
title = {Solidification of undercooled peritectic Fe-Ge alloy},
journal = {Acta Materialia},
year = {2005},
volume = {53},
number = {13},
pages = {3591-3600},
note = {cited By (since 1996) 10},
doi = {10.1016/j.actamat.2005.03.053}
}
|
| Biswas K, Phanikumar G, Chattopadhyay K, Volkmann T, Funke O, Holland-Moritz D and Herlach D (2004), "Rapid solidification behaviour of undercooled levited Fe-Ge alloy droplets", Materials Science and Engineering A. Vol. 375-377(1-2 SPEC. ISS.), pp. 464-467. |
| Abstract: The solidification behaviour of Fe82Ge18 and Fe75Ge25 alloys is studied by using an electromagnetic levitation facility. The maximum undercooling attained in the case of Fe82Ge18 alloy is 240 K. Growth velocity of α- (bcc) phase is measured using a photodiode technique and shows two distinct regimes. In the case of Fe75Ge25, the maximum undercooling attained is 165 K. At low undercoolings two recalescence events occur, corresponding to formation of α- and ε-phase (DO19). At large undercoolings the peritectic reaction (α+liquid→ε) is suppressed. Microstructural analysis indicates morphological changes in the microstructure as well as a competition among phases nucleating at different levels of undercooling. © 2003 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Biswas2004464,
author = {Biswas, K. and Phanikumar, G. and Chattopadhyay, K. and Volkmann, T. and Funke, O. and Holland-Moritz, D. and Herlach, D.M.},
title = {Rapid solidification behaviour of undercooled levited Fe-Ge alloy droplets},
journal = {Materials Science and Engineering A},
year = {2004},
volume = {375-377},
number = {1-2 SPEC. ISS.},
pages = {464-467},
note = {cited By (since 1996) 3},
doi = {10.1016/j.msea.2003.10.047}
}
|
| Galenko PK, Heralch DM, Funke O and Phanikumar G (2004), "Solidification and Crystallization" , pp. 52. Wiley-VCH. |
BibTeX:
@inbook{Galenko2004,
author = {Peter K Galenko and Dieter M Heralch and Oliver Funke and Gandham Phanikumar},
editor = {Dieter M. Herlach},
title = {Solidification and Crystallization},
publisher = {Wiley-VCH},
year = {2004},
pages = {52},
url = {https://www.researchgate.net/profile/Patricia_Carvalho4/publication/259088626_Solidification_and_Crystallization/links/00463529f4bdb335d0000000.pdf#page=71}
}
|
| Herlach D, Funke O, Gandham P and Galenko P (2004), "Free dendrite growth in undercooled melts: Experiments and modeling", Solidification Processes and Microstructures: A Symposium in Honor of Wilfried Kurz., In Solidification Processes and Microstructures: A symposium in honor of Wilfried Kurz. Warrendale, PA, USA (978-0-87339-572-4), pp. 277-288. TMS. |
| Abstract: Essential progress of modeling of free dendrite growth in undercooled melts was achieved by the "classic" work of Wilfried Kurz et al. In the present paper, recent developments in experimental methods are described to measure the dendrite growth dynamics in undercooled metallic melts, which are containerlessly processed by electromagnetic levitation technique. Results of essentially improved accuracy in measuring the dendrite growth velocity as a function of undercooling are presented for "nominally" pure nickel. In parallel, the sharp interface dendrite growth theory is extended to include effects both of melt convection and electromagnetically induced stirring of the levitation processed liquid. The analysis of the results indicate that fluid flow causes an enhancement of the dendrite velocity in the small undercooling range. Also, small amounts of impurities in nickel can lead to an increase of the growth velocity but with a temperature characteristics being different from that of the effect by fluid flow. This allows to discriminate between both contributions as it is shown by experimental investigations and modeling within the extended sharp interface model and phase-field modeling as well. |
BibTeX:
@conference{Herlach2004277,
author = {Herlach, D.M. and Funke, O. and Gandham, P. and Galenko, P.},
editor = {Michel Rappaz and Christoph Beckermann and Rohit Trivedi},
title = {Free dendrite growth in undercooled melts: Experiments and modeling},
booktitle = {Solidification Processes and Microstructures: A symposium in honor of Wilfried Kurz},
journal = {Solidification Processes and Microstructures: A Symposium in Honor of Wilfried Kurz},
publisher = {TMS},
year = {2004},
number = {978-0-87339-572-4},
pages = {277-288},
note = {cited By (since 1996) 2},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Herlach_TMS2004p277.pdf}
}
|
| Phanikumar G, Dutta P and Chattopadhyay K (2004), "Computational modeling of laser welding of Cu-Ni dissimilar couple", Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science. Vol. 35(2), pp. 339-350. |
| Abstract: A three-dimensional transient model to solve heat transfer, fluid flow, and species conservation during laser welding of dissimilar metals is presented. The model is based on a control volume formulation with an enthalpy-porosity technique to handle phase change and a mixture model to simulate mixing of molten metals. Weld pool development, solidified weld pool shape, and composition profiles are presented for both stationary as well as continuous laser welding in conduction mode. Salient features of a dissimilar Cu-Ni weld are summarized and thermal transport arguments are employed to successfully explain the observations. It is found that the weld pool shape becomes asymmetric even when the heat source is symmetrically applied on the two metals forming the couple. It is also observed that convection plays an important role in the development of weld pool shape and composition profiles. As the weld pool develops, the side melting first (nickel) is found to experience more convection and better mixing. Results from the case studies of computation are compared with corresponding experimental observations, showing good qualitative agreement between the two. |
BibTeX:
@article{Phanikumar2004339,
author = {Phanikumar, G. and Dutta, P. and Chattopadhyay, K.},
title = {Computational modeling of laser welding of Cu-Ni dissimilar couple},
journal = {Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science},
year = {2004},
volume = {35},
number = {2},
pages = {339-350},
note = {cited By (since 1996) 14},
url = {https://link.springer.com/article/10.1007/s11663-004-0034-4},
doi = {10.1007/s11663-004-0034-4}
}
|
| Phanikumar G, Dutta P, Galun R and Chattopadhyay K (2004), "Microstructural evolution during remelting of laser surface alloyed hyper-monotectic Al-Bi alloy", Materials Science and Engineering A. Vol. 371(1-2), pp. 91-102. |
| Abstract: The present investigation explores the possibility of synthesizing a two-phase microstructure consisting of a fine dispersion of bismuth particles in an aluminium matrix using the laser surface alloying technique. The possibility of controlling the size distribution of bismuth particles by subsequent remelting is also investigated. The microstructural analysis of the surface alloyed samples shows that the average size of the bismuth particles reduces with increase in laser scan speed. In order to understand the factors that determine the nature of the size distribution of the particles, a detailed model is developed. The model incorporates heat and fluid flow induced by the laser to arrive at the evolution of the temperature and velocity of the melt in three dimensions. Using these as inputs, a kinetic analysis of the nucleation, growth and coarsening induced by collision-controlled coalescence of the bismuth particles from the melt is carried out. Comparison with the experiments indicates that coalescence due to convection plays an important role in the evolution of the size distribution of bismuth particles. © 2003 Elsevier B.V. All rights reserved. |
BibTeX:
@article{Phanikumar200491,
author = {Phanikumar, G. and Dutta, P. and Galun, R. and Chattopadhyay, K.},
title = {Microstructural evolution during remelting of laser surface alloyed hyper-monotectic Al-Bi alloy},
journal = {Materials Science and Engineering A},
year = {2004},
volume = {371},
number = {1-2},
pages = {91-102},
note = {cited By (since 1996) 10},
url = {https://www.sciencedirect.com/science/article/pii/S0921509303009572},
doi = {10.1016/j.msea.2003.09.071}
}
|
| Bysakh S, Mitra S, Phanikumar G, Mazumder J, Dutta P and Chattopadhyay K (2003), "Characterization of microstructure in laser-surface-alloyed layers of aluminum on nickel", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. Vol. 34 A(11), pp. 2621-2631. |
| Abstract: In order to obtain basic understanding of microstructure evolution in laser-surface-alloyed layers, aluminum was surface alloyed on a pure nickel substrate using a CO2 laser. By varying the laser scanning speed, the composition of the surface layers can be systematically varied. The Ni content in the layer increases with increase in scanning speed. Detailed cross-sectional transmission electron microscopic study reveals complexities in solidification behavior with increased nickel content. It is shown that ordered B2 phase forms over a wide range of composition with subsequent precipitation of Ni2Al, an ordered ω phase in the B2 matrix, during solid-state cooling. For nickel-rich alloys associated with higher laser scan speed, the fcc γ phase is invariably the first phase to grow from the liquid with solute trapping. The phase reorders in the solid state to yield γ′ Ni3Al. The phase competes with β AlNi, which forms massively from the liquid. The β AlNi transforms martensitically to a 3R structure during cooling in solid state. The results can be rationalized in terms of a metastable phase diagram proposed earlier. However, the results are at variance with earlier studies of laser processing of nickel-rich alloys. |
BibTeX:
@article{Bysakh20032621,
author = {Bysakh, S. and Mitra, S.K. and Phanikumar, G. and Mazumder, J. and Dutta, P. and Chattopadhyay, K.},
title = {Characterization of microstructure in laser-surface-alloyed layers of aluminum on nickel},
journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},
year = {2003},
volume = {34 A},
number = {11},
pages = {2621-2631},
note = {cited By (since 1996) 9},
url = {https://link.springer.com/article/10.1007%2Fs11661-003-0021-4},
doi = {10.1007/s11661-003-0021-4}
}
|
| Sarkar S, Raj P, Chakraborty S, Phanikumar G, Chattopadhyay K and Dutta P (2003), "Transport phenomena in laser surface alloying", Journal of Materials Science. Vol. 38(1), pp. 155-164. |
| Abstract: A three dimensional, transient model is developed for studying heat transfer, fluid flow and mass transfer for the case of a single-pass laser surface alloying process. The numerical study is performed in a co-ordinate system fixed to the laser which moves with a constant scanning speed. The coupled momentum, energy and species conservation equations are solved using a finite volume technique. Phase change processes are modelled using a fixed-grid enthalpy-porosity technique, which is capable of predicting the continuously evolving solid-liquid interface. The three-dimensional model is able to predict the species concentration distribution inside the molten pool during alloying, as well as in the entire cross section of the solidified alloy. Corresponding experimental results show a good qualitative agreement with the numerical predictions with regard to pool shape and final composition distribution. |
BibTeX:
@article{Sarkar2003155,
author = {Sarkar, S. and Raj, P.M. and Chakraborty, S. and Phanikumar, G. and Chattopadhyay, K. and Dutta, P.},
title = {Transport phenomena in laser surface alloying},
journal = {Journal of Materials Science},
year = {2003},
volume = {38},
number = {1},
pages = {155-164},
note = {cited By (since 1996) 9},
url = {https://link.springer.com/article/10.1023%2FA%3A1021134404356},
doi = {10.1023/A:1021134404356}
}
|
| Kumar K, Phanikumar G, Dutta P and Chattopadhyay K (2002), "Microstructural development of dissimilar weldments: Case of MiG welding of Cu with Fe filler", Journal of Materials Science. Vol. 37(11), pp. 2345-2349. |
| Abstract: Microstructure development during MIG welding of copper with iron filler has been studied to gain insight to the process of dissimilar welding. The microstructure of the iron rich bids consist of martensitic bcc iron with cellular network of fcc copper. The scale of network depends on the processing conditions. However, the average composition remains fairly uniform with 20at% Cu excepting at the boundary regions of the bid and the copper plates. A characteristic banded structure could be observed in these regions whose width scales with traverse speed. Evidence of phase separated copper globule suggests access to the submerged miscibility gap and significant undercooling of the melt during welding. © 2002 Kluwer Academic Publishers. |
BibTeX:
@article{Kumar20022345,
author = {Kumar, K.S. and Phanikumar, G. and , Dutta, P. and Chattopadhyay, K.},
title = {Microstructural development of dissimilar weldments: Case of MiG welding of Cu with Fe filler},
journal = {Journal of Materials Science},
year = {2002},
volume = {37},
number = {11},
pages = {2345-2349},
note = {cited By (since 1996) 4},
url = {https://link.springer.com/article/10.1023%2FA%3A1015306408611},
doi = {10.1023/A:1015306408611}
}
|
| Mohan Raj P, Sarkar S, Chakraborty S, Phanikumar G, Dutta P and Chattopadhyay K (2002), "Modelling of transport phenomena in laser surface alloying with distributed species mass source", International Journal of Heat and Fluid Flow. Vol. 23(3), pp. 298-307. |
| Abstract: In this paper, a three-dimensional transient macroscopic numerical model is developed for the description of transport phenomena during laser surface alloying. In order to make accurate estimates for the species composition distribution during the process, the addition of alloying elements is formulated by devising a species generation term for the solute transport equation. By employing a particle-tracking algorithm and a simultaneous particle-melting consideration, the species source term is estimated by the amount of fusion of a spherical particle as it passes through a particular control volume. Numerical simulations are performed for two cases. The first case corresponds to aluminium as alloying element on a nickel substrate, while the second case is for alloying nickel on aluminium substrate. It is observed for the latter case that the melting of the alloying element is not instantaneous, and hence it cannot be modelled as a species mass flux boundary condition at the top surface. The predicted results are compared with experiments, and the agreement is found to be good. © 2002 Published by Elsevier Science Inc. |
BibTeX:
@article{MohanRaj2002298,
author = {Mohan Raj, P. and Sarkar, S. and Chakraborty, S. and Phanikumar, G. and Dutta, P. and Chattopadhyay, K.},
title = {Modelling of transport phenomena in laser surface alloying with distributed species mass source},
journal = {International Journal of Heat and Fluid Flow},
year = {2002},
volume = {23},
number = {3},
pages = {298-307},
note = {cited By (since 1996) 21},
url = {https://www.sciencedirect.com/science/article/pii/S0142727X02001777},
doi = {10.1016/S0142-727X(02)00177-7}
}
|
| Phanikumar G (2002), "Experimental and Computational Studies on Laser Processing of Dissimilar Metals". Thesis at: Indian Institute of Science, Bangalore. IISc Bangalore, 560012, India, March, 2002. |
BibTeX:
@phdthesis{Phanikumar2002,
author = {Phanikumar, G.},
title = {Experimental and Computational Studies on Laser Processing of Dissimilar Metals},
school = {Indian Institute of Science, Bangalore},
year = {2002},
url = {https://mme.iitm.ac.in/gphani/assets/publications/gpthesisfull.pdf}
}
|
| Maiwald T, Galun R, Mordike BL, Chattopadhayay K and Phanikumar G (2002), "Laser Cladding with Alloy Systems with a Miscibility Gap in the Liquid State", In Proceedings of the International Conference on Advances in Materials and Materials Processing ICAMMP. Kharagpur, India , pp. 831-835. Tata McGraw Hill Publishers, Delhi.
[BibTeX] |
BibTeX:
@conference{T.Maiwald2002,
author = {T. Maiwald and R. Galun and B. L. Mordike and K. Chattopadhayay and G. Phanikumar},
editor = {N. Chakrabarty and U.K. Chatterjee},
title = {Laser Cladding with Alloy Systems with a Miscibility Gap in the Liquid State},
booktitle = {Proceedings of the International Conference on Advances in Materials and Materials Processing ICAMMP},
publisher = {Tata McGraw Hill Publishers, Delhi},
year = {2002},
pages = {831--835}
}
|
| Chattopadhyay K, Biswas K, Bysakh S, Phanikumar G., Weisheit A., Galun R. and Mordike B (2001), "Quasicrystalline coatings through laser processing: A study on process optimisation and microstructure evolution", Materials Research Society Symposium - Proceedings. Vol. 643, pp. K1531-K15312. |
| Abstract: Composite coatings containing quasicrystalline (QC) phases in Al-Cu-Fe alloys were prepared by laser cladding using a mixture of the elemental powders. Two substrates, namely pure aluminum and an Al-Si alloy were used. The clad layers were remelted at different scanning velocities to alter the growth conditions of different phases. The process parameters were optimized to produce quasicrystalline phases. The evolution of the microstructure in the coating layer was characterized by detailed microstructural investigation. The results indicate presence of quasicrystals in the aluminum substrate. However, only approximant phase could be observed in the substrate of Al-Si alloys. It is shown that there is a significant transport of Si atoms from the substrate to the clad layer during the cladding and remelting process. The hardness profiles of coatings on aluminum substrate indicate a very high hardness. The coating on Al-Si alloy, on the other hand, is ductile and soft. The fracture toughness of the hard coating on aluminum was obtained by nano-indentation technique. The K1C value was found to be 1.33 MPa m1/2 which is typical of brittle materials. |
BibTeX:
@conference{Chattopadhyay2001,
author = {Chattopadhyay, K. and Biswas, K. and Bysakh, S. and Phanikumar, G., and Weisheit, A., and Galun, R., and Mordike, B.},
title = {Quasicrystalline coatings through laser processing: A study on process optimisation and microstructure evolution},
journal = {Materials Research Society Symposium - Proceedings},
year = {2001},
volume = {643},
pages = {K1531-K15312},
note = {cited By (since 1996) 1},
url = {https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/quasicrystalline-coatings-through-laser-processing-a-study-on-process-optimisation-and-microstructure-evolution/5A07D4A3DC1A84A3E2477C3A993D24B6},
doi = {10.1557/PROC-643-K15.3}
}
|
| Chattopadhyay K, Sanyal S, Phanikumar G, Mordike B and Galun R (2001), "Microstructure study of laser surface cladding of bearing materials", In Proceedings of Materials Week. Frankfurt, Germany (388) |
BibTeX:
@conference{Chattopadhyay2001a,
author = {Chattopadhyay, K. and Sanyal, S. and Phanikumar, G. and Mordike, B.L. and Galun, R.},
title = {Microstructure study of laser surface cladding of bearing materials},
booktitle = {Proceedings of Materials Week},
year = {2001},
number = {388},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Chattopadhyay_MW2001pap388.pdf}
}
|
| Phanikumar G, Dutta P and Chattopadhay K (2001), "Solidification microstructures in laser welding of dissimilar metals", In Proceedings of Second International Conference of Solidification Science and Processing. , pp. 155-162. Science Publishers, Inc., Enfield, USA. |
BibTeX:
@conference{Phanikumar2001,
author = {Phanikumar, G. and Dutta, P. and Chattopadhay, K.},
editor = {B.K. Dhindaw and B.S. Murty and S. Sen},
title = {Solidification microstructures in laser welding of dissimilar metals},
booktitle = {Proceedings of Second International Conference of Solidification Science and Processing},
publisher = {Science Publishers, Inc., Enfield, USA},
year = {2001},
pages = {155--162},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Phanikumar_ICSSP2001p155.pdf}
}
|
| Phanikumar G, Chattopadhyay K and Dutta P (2001), "Modelling of transport phenomena in laser welding of dissimilar metals", International Journal of Numerical Methods for Heat and Fluid Flow. Vol. 11(2), pp. 156-171. |
| Abstract: The transport phenomena (heat transfer, fluid flow and species distribution) are numerically modelled for the case of laser welding of dissimilar metals. The model involves convection in the weld pool along with melting and mixing. The associated metallurgical phenomenon is an extremely complex one, and the present work is a preliminary attempt to model the process after making suitable assumptions. The numerical study is performed using a pressure based finite volume technique after making appropriate modifications to the algorithm to include the associated phase change processes and dissimilarity in the metal properties. The phase change process is modelled using an enthalpy-porosity technique, while the dissimilar metal properties are handled using appropriate mixture theories. As a case study, we have used dissimilar couples of copper-nickel. It is observed that the weld pool shape becomes asymmetric even when the heat source is symmetrically applied on the two metals forming the couple. As the weld pool develops, the side melting earlier is found to experience more convection and better mixing. Corresponding experiments are performed using the same parameters as in the computations, showing a good qualitative agreement between the two results. A scale analysis is performed to predict the time scale of initiation of melting of each metal. The scale-analysis predictions show a good agreement with the numerical results. |
BibTeX:
@article{Phanikumar2001156,
author = {Phanikumar, G. and Chattopadhyay, K. and Dutta, P.},
title = {Modelling of transport phenomena in laser welding of dissimilar metals},
journal = {International Journal of Numerical Methods for Heat and Fluid Flow},
year = {2001},
volume = {11},
number = {2},
pages = {156-171},
note = {cited By (since 1996) 17},
url = {https://www.emerald.com/insight/content/doi/10.1108/09615530110381575/full/html},
doi = {10.1108/09615530110381575}
}
|
| Phanikumar G and Chattopadhyay K (2001), "Solidification microstructure development", Sadhana - Academy Proceedings in Engineering Sciences. Vol. 26(1-2), pp. 25-34. |
| Abstract: In the present article, evolution of microstructure during solidification, as a function of various parameters, is discussed. Macrosegregation is described as being due to insufficient diffusivity of solute in the solid. Pattern formation is discussed in the light of instabilities at the solidification growth front. An overview of the scaling relations for various microstructures is given. Metastable extensions to equilibrium phase diagrams and corrections to equilibrium quantities are described. |
BibTeX:
@article{Phanikumar200125,
author = {Phanikumar, G. and Chattopadhyay, K.},
title = {Solidification microstructure development},
journal = {Sadhana - Academy Proceedings in Engineering Sciences},
year = {2001},
volume = {26},
number = {1-2},
pages = {25-34},
note = {cited By (since 1996) 5},
url = {http://www.ias.ac.in/sadhana/Pdf2001FebApr/Pe926.pdf},
doi = {10.1007/BF02728477}
}
|
| Phanikumar G, Basu B, Chakraborty S, Chattopadhay K, Dutta P and Majumdar J (2000), "Laser Surface Alloying of Aluminium on Iron Substrate: Experiments and Numerical Simulation", In Proceedings of Euromat 99: Symposium G5 - Surface Technology / Laser Surface Treatment. |
BibTeX:
@conference{Phanikumar1999,
author = {G. Phanikumar and B. Basu and S. Chakraborty and K. Chattopadhay and P. Dutta and J. Majumdar},
title = {Laser Surface Alloying of Aluminium on Iron Substrate: Experiments and Numerical Simulation},
booktitle = {Proceedings of Euromat 99: Symposium G5 - Surface Technology / Laser Surface Treatment},
year = {2000},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Phanikumar_Euromat99v11p425.pdf}
}
|
| Phanikumar G, Dutta P and Chattopadhyay K (2000), "Laser processing of dissimilar metals", In Proceedings of Int. Symposium on Materials Ageing and Life Management (ISOMALM). Kalpakkam, India Allied Publishers Ltd., Chennai, India. |
BibTeX:
@conference{Phanikumar2000,
author = {G. Phanikumar and P. Dutta and K. Chattopadhyay},
editor = {Baldev Raj, K.Bhanu Sankara Rao, T.Jayakumar, and R.K.Dayal},
title = {Laser processing of dissimilar metals},
booktitle = {Proceedings of Int. Symposium on Materials Ageing and Life Management (ISOMALM)},
publisher = {Allied Publishers Ltd., Chennai, India},
year = {2000},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Phanikumar_ISOMALM200.pdf}
}
|
| Phanikumar G, Chattopadhyay K and Dutta P (2000), "Supercomputing applications in materials engineering", Current Science. Vol. 78(7), pp. 847-849. |
| Abstract: We review some of the materials processing problems that are being tackled by the scientific community today in the light of the high computing power available at affordable costs. Simulation challenges related to materials processing that once were thought of as impossible to tackle by computational methods are now feasible and are highlighted. As an illustration, computer simulation of materials joining is detailed. |
BibTeX:
@article{Phanikumar2000847,
author = {Phanikumar, G. and Chattopadhyay, K. and Dutta, P.},
title = {Supercomputing applications in materials engineering},
journal = {Current Science},
year = {2000},
volume = {78},
number = {7},
pages = {847-849},
note = {cited By (since 1996) 0},
url = {http://www.iisc.ernet.in/currsci/apr102000/surveys3.pdf}
}
|
| Phanikumar G, Chattopadhyay K and Dutta P (2000), "Mathematical Modelling of Weld Phenomena V" Institute of Materials, London
[BibTeX] |
BibTeX:
@inbook{Phanikumar2000a,
author = {G. Phanikumar and K. Chattopadhyay and P. Dutta},
editor = {H. Cerjak},
title = {Mathematical Modelling of Weld Phenomena V},
year = {2000}
}
|
| Phanikumar G, Pardeshi R, Chattopadhyay K, Dutta P and Majumder J (1999), "Dissimilar Metal Welding of Copper Nickel Couple by Continuous Wave CO 2 Laser", ASM Proceedings of the International Conference: Trends in Welding Research., In Trends in Welding Research. Ohio, USA , pp. 461-466. ASM. |
| Abstract: The laser welding of dissimilar metal by continuous wave CO2 laser was discussed. High purity copper and Nickel were taken in the form of bars and were fixed on a carbon nanotube table in butt-weld geometry. It was shown that nickel weld interface is sharp and cellular growth of the base metal was observed in to the weldments. The model presented in the article was able to display some of the key features of the process observed experimentally. |
BibTeX:
@conference{Phanikumar1998461,
author = {Phanikumar, G. and Pardeshi, R. and Chattopadhyay, K. and Dutta, P and Majumder, J.},
editor = {John. M. Vitek and Stan A. David and John A. Johnson and Herschel B. Smartt and Tarasankar Debroy},
title = {Dissimilar Metal Welding of Copper Nickel Couple by Continuous Wave CO 2 Laser},
booktitle = {Trends in Welding Research},
journal = {ASM Proceedings of the International Conference: Trends in Welding Research},
publisher = {ASM},
year = {1999},
pages = {461-466},
note = {ISBN: 0-87170-627-X},
url = {https://mme.iitm.ac.in/gphani/assets/publications/Phanikumar_ASM1998p641.pdf}
}
|