The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
N. Orhan - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the superplasticity behavior of ultrahigh carbon steel
Materials & Design, 2005Co-Authors: N. Özdemir, N. OrhanAbstract:Abstract In this study, the superplasticity behavior of grain-refinement ultrahigh carbon (UHC) steel with thermomechanical process and having an average grain size of 3 μm was investigated at the Eutectoid Transformation points of this material with the stepped strain rates between 2 × 10 −3 and 1.6 × 10 −2 s −1 test method. The results showed that the best superplasticity was obtained at 735 °C and in the deformation rate range between 3.3 × 10 −3 and 4.6 × 10 −3 s −1 . The deformation rate sensitivity exponent, m , was calculated as 0.58 in this range.
Britta Nestler - One of the best experts on this subject based on the ideXlab platform.
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Deviations from cooperative growth mode during Eutectoid Transformation: Mechanisms of polycrystalline Eutectoid evolution in Fe-C steels
Acta Materialia, 2015Co-Authors: Kumar Ankit, Rajdip Mukherjee, Britta NestlerAbstract:Abstract Undercooling (below A1 temperature) and spacing between the preexisting cementite particles are known to be the factors that determine whether the isothermal Eutectoid Transformation in Fe-C proceeds in cooperative (resulting in lamellar pearlite) or non-cooperative mode (yielding divorced Eutectoid). Typically, a divorced Eutectoid microstructure consists of a fine dispersion of cementite in the ferritic matrix. Although, numerous experimental studies report a bimodal size distribution of cementite in the transformed Eutectoid microstructure, the factors that facilitate the shift from a characteristic unimodal to bimodal size distribution have not been reported extensively. In the present work, we adopt a multiphase-field approach to study the morphological transition during isothermal Eutectoid Transformation which proceeds from an initial configuration comprising of a random distribution of cementite particles and grain boundary ferrite layers embedded in polycrystalline austenite. By conducting a systematic parametric study, we deduce the influence of preexisting arrangement of cementite, grain boundary ferrite thickness and prior austenite grain size on the mechanism by which Eutectoid phases evolve. We also establish a synergy between the numerically simulated cementite morphologies and spatial configurations with those observed in experimental microstructures. Finally, we discuss the influence of the different factors that lead to the formation of mixed cementite morphologies (spheroidal and non-spheroidal) in the transformed microstructure and highlight the importance of 3D simulations.
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Evolution of mixed cementite morphologies during non-cooperative Eutectoid Transformation in Fe–C steels
Computational Materials Science, 2015Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:Abstract We numerically investigate the characteristics of concurrent carbon redistribution pathways, as the ferrite–austenite front evolves during an isothermal Eutectoid Transformation starting from a random distribution of preexisting cementite particle. By analyzing the influence of initial interparticle spacing, arrangement and undercooling (below A 1 temperature) on the curvature-driven coarsening, we generalize the present criteria of non-cooperative Eutectoid Transformation. We also propose plausible mechanisms that result in mixed cementite morphologies (spherical and non-spherical) in the transformed microstructure. For the chosen set of parameters, the present phase-field simulations suggest a strong competition between the cooperative, non-cooperative and coarsening regimes, as the Transformation proceeds. The predominance of one or more of the three regimes during the intermittent stages, which depend on the local conditions, determine the cementite size distribution in the transformed microstructure.
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Evolution of mixed cementite morphologies during non-cooperative Eutectoid Transformation in Fe-C steels Accepted in Computational Materials Science
2015Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:We numerically investigate the characteristics of concurrent carbon redistribution pathways, as the ferrite-austenite front evolves during an isothermal Eutectoid Transformation starting from a random distribution of preexisting cementite particle. By analyzing the influence of initial interparticle spacing, arrangement and undercooling (below A1 temperature) on the curvature-driven coarsening, we generalize the present criteria of non-cooperative Eutectoid Transformation. We also propose plausible mechanisms that result in mixed cementite morphologies (spherical and non-spherical) in the transformed microstructure. For the chosen set of parameters, the present phase-field simulations suggest a strong competition between the cooperative, non-cooperative and coarsening regimes, as the Transformation proceeds. The predominance of one or more of the three regimes during the intermittent stages, which depend on the local conditions, determine the cementite size distribution in the transformed microstructure.
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Deviations from cooperative growth mode during Eutectoid Transformation: Insights from a phase-field approach
Acta Materialia, 2014Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:The non-cooperative Eutectoid Transformation relies on the presence of pre-existing cementite particles in the parent austenitic phase and yields a product, popularly known as the divorced Eutectoid. Under isothermal conditions, two of the important parameters that influence the Transformation mechanism and determine the final morphology are undercooling (below the A1temperature) and interparticle spacing. Although the criteria that govern the morphological transition from lamellar to divorced is experimentally well established, numerical studies giving a detailed exposition of the non-cooperative Transformation mechanism have not been reported extensively. In the present work, we employ a multiphase-field model that uses thermodynamic information from the CALPHAD database to numerically simulate the pulling-away of the advancing ferrite-austenite interface from cementite, which results in a transition from lamellar to divorced Eutectoid morphology in Fe-C alloy. We also identify the onset of a concurrent growth and coarsening regime at small interparticle spacing and low undercooling. We analyze the simulation results to unravel the essential physics behind this complex spatial and temporal evolution pathway and amend the existing criteria by constructing a Lamellar-Divorced-Coarsening (LDC) map.
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Deviations from cooperative growth mode during Eutectoid Transformation: insights from phase-field approach Accepted in Acta Materialia
2014Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:The non-cooperative Eutectoid Transformation relies on the presence of pre-existing cementite particles in the parent austenitic phase and yields a product, popularly known as the divorced Eutectoid. In isothermal conditions, two of the important parameters, which influence the Transformation mechanism and determine the final morphology are undercooling (below A1 temperature) and interparticle spacing. Although, the criteria which governs the morphological transition from lamellar to divorced is experimentally well established, numerical studies that give a detailed exposition of the non-cooperative Transformation mechanism, have not been reported extensively. In the present work, we employ a multiphase-field model, that uses the thermodynamic information from the CALPHAD database, to numerically simulate the pulling-away of the advancing ferrite-austenite interface from cementite, which results in a transition from lamellar to divorced Eutectoid morphology in Fe-C alloy. We also identify the onset of a concurrent growth and coarsening regime at small inter-particle spacing and low undercooling. We analyze the simulation results to unravel the essential physics behind this complex spacial and temporal evolution pathway and amend the existing criteria by constructing a Lamellar-Divorced-Coarsening (LDC) map.
Peter C. Collins - One of the best experts on this subject based on the ideXlab platform.
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On the Eutectoid Transformation behavior of the Ti-Zn system and its metastable phases
Journal of Alloys and Compounds, 2017Co-Authors: David A. Brice, P. Samimi, Iman Ghamarian, Yue Liu, Michael Mendoza, Michael Joseph Kenney, Richard F. Reidy, Matias Garcia-avila, Peter C. CollinsAbstract:Abstract To date, Zn has not been used as an alloying addition in structural Ti alloys. The main obstacle has been the disparity between their melting and vaporization temperatures. A novel processing technique was developed to create a Ti-Zn compound. The equilibrium phases and microstructures were studied by electron microscopy and x-ray diffraction techniques. Results show the presence of pearlitic domains of α-Ti (hexagonal closed packed crystal structure) and Ti 2 Zn (body center tetragonal structure) in regions that have a near Eutectoid composition. Solutionizing and water quenching results in the formation of martensite along with intermetallic laths, suggesting that the Eutectoid Transformation is active.
N. Özdemir - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the superplasticity behavior of ultrahigh carbon steel
Materials & Design, 2005Co-Authors: N. Özdemir, N. OrhanAbstract:Abstract In this study, the superplasticity behavior of grain-refinement ultrahigh carbon (UHC) steel with thermomechanical process and having an average grain size of 3 μm was investigated at the Eutectoid Transformation points of this material with the stepped strain rates between 2 × 10 −3 and 1.6 × 10 −2 s −1 test method. The results showed that the best superplasticity was obtained at 735 °C and in the deformation rate range between 3.3 × 10 −3 and 4.6 × 10 −3 s −1 . The deformation rate sensitivity exponent, m , was calculated as 0.58 in this range.
Kumar Ankit - One of the best experts on this subject based on the ideXlab platform.
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Deviations from cooperative growth mode during Eutectoid Transformation: Mechanisms of polycrystalline Eutectoid evolution in Fe-C steels
Acta Materialia, 2015Co-Authors: Kumar Ankit, Rajdip Mukherjee, Britta NestlerAbstract:Abstract Undercooling (below A1 temperature) and spacing between the preexisting cementite particles are known to be the factors that determine whether the isothermal Eutectoid Transformation in Fe-C proceeds in cooperative (resulting in lamellar pearlite) or non-cooperative mode (yielding divorced Eutectoid). Typically, a divorced Eutectoid microstructure consists of a fine dispersion of cementite in the ferritic matrix. Although, numerous experimental studies report a bimodal size distribution of cementite in the transformed Eutectoid microstructure, the factors that facilitate the shift from a characteristic unimodal to bimodal size distribution have not been reported extensively. In the present work, we adopt a multiphase-field approach to study the morphological transition during isothermal Eutectoid Transformation which proceeds from an initial configuration comprising of a random distribution of cementite particles and grain boundary ferrite layers embedded in polycrystalline austenite. By conducting a systematic parametric study, we deduce the influence of preexisting arrangement of cementite, grain boundary ferrite thickness and prior austenite grain size on the mechanism by which Eutectoid phases evolve. We also establish a synergy between the numerically simulated cementite morphologies and spatial configurations with those observed in experimental microstructures. Finally, we discuss the influence of the different factors that lead to the formation of mixed cementite morphologies (spheroidal and non-spheroidal) in the transformed microstructure and highlight the importance of 3D simulations.
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Evolution of mixed cementite morphologies during non-cooperative Eutectoid Transformation in Fe–C steels
Computational Materials Science, 2015Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:Abstract We numerically investigate the characteristics of concurrent carbon redistribution pathways, as the ferrite–austenite front evolves during an isothermal Eutectoid Transformation starting from a random distribution of preexisting cementite particle. By analyzing the influence of initial interparticle spacing, arrangement and undercooling (below A 1 temperature) on the curvature-driven coarsening, we generalize the present criteria of non-cooperative Eutectoid Transformation. We also propose plausible mechanisms that result in mixed cementite morphologies (spherical and non-spherical) in the transformed microstructure. For the chosen set of parameters, the present phase-field simulations suggest a strong competition between the cooperative, non-cooperative and coarsening regimes, as the Transformation proceeds. The predominance of one or more of the three regimes during the intermittent stages, which depend on the local conditions, determine the cementite size distribution in the transformed microstructure.
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Evolution of mixed cementite morphologies during non-cooperative Eutectoid Transformation in Fe-C steels Accepted in Computational Materials Science
2015Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:We numerically investigate the characteristics of concurrent carbon redistribution pathways, as the ferrite-austenite front evolves during an isothermal Eutectoid Transformation starting from a random distribution of preexisting cementite particle. By analyzing the influence of initial interparticle spacing, arrangement and undercooling (below A1 temperature) on the curvature-driven coarsening, we generalize the present criteria of non-cooperative Eutectoid Transformation. We also propose plausible mechanisms that result in mixed cementite morphologies (spherical and non-spherical) in the transformed microstructure. For the chosen set of parameters, the present phase-field simulations suggest a strong competition between the cooperative, non-cooperative and coarsening regimes, as the Transformation proceeds. The predominance of one or more of the three regimes during the intermittent stages, which depend on the local conditions, determine the cementite size distribution in the transformed microstructure.
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Deviations from cooperative growth mode during Eutectoid Transformation: Insights from a phase-field approach
Acta Materialia, 2014Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:The non-cooperative Eutectoid Transformation relies on the presence of pre-existing cementite particles in the parent austenitic phase and yields a product, popularly known as the divorced Eutectoid. Under isothermal conditions, two of the important parameters that influence the Transformation mechanism and determine the final morphology are undercooling (below the A1temperature) and interparticle spacing. Although the criteria that govern the morphological transition from lamellar to divorced is experimentally well established, numerical studies giving a detailed exposition of the non-cooperative Transformation mechanism have not been reported extensively. In the present work, we employ a multiphase-field model that uses thermodynamic information from the CALPHAD database to numerically simulate the pulling-away of the advancing ferrite-austenite interface from cementite, which results in a transition from lamellar to divorced Eutectoid morphology in Fe-C alloy. We also identify the onset of a concurrent growth and coarsening regime at small interparticle spacing and low undercooling. We analyze the simulation results to unravel the essential physics behind this complex spatial and temporal evolution pathway and amend the existing criteria by constructing a Lamellar-Divorced-Coarsening (LDC) map.
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Deviations from cooperative growth mode during Eutectoid Transformation: insights from phase-field approach Accepted in Acta Materialia
2014Co-Authors: Kumar Ankit, Tobias Mittnacht, Rajdip Mukherjee, Britta NestlerAbstract:The non-cooperative Eutectoid Transformation relies on the presence of pre-existing cementite particles in the parent austenitic phase and yields a product, popularly known as the divorced Eutectoid. In isothermal conditions, two of the important parameters, which influence the Transformation mechanism and determine the final morphology are undercooling (below A1 temperature) and interparticle spacing. Although, the criteria which governs the morphological transition from lamellar to divorced is experimentally well established, numerical studies that give a detailed exposition of the non-cooperative Transformation mechanism, have not been reported extensively. In the present work, we employ a multiphase-field model, that uses the thermodynamic information from the CALPHAD database, to numerically simulate the pulling-away of the advancing ferrite-austenite interface from cementite, which results in a transition from lamellar to divorced Eutectoid morphology in Fe-C alloy. We also identify the onset of a concurrent growth and coarsening regime at small inter-particle spacing and low undercooling. We analyze the simulation results to unravel the essential physics behind this complex spacial and temporal evolution pathway and amend the existing criteria by constructing a Lamellar-Divorced-Coarsening (LDC) map.
