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[P91] Thermodynamic and Kinetic Modeling of the Ferrite-Austenite Phase Transformation
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Y. DU et al. / CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry 51 (2015) 344–415
incongruently melting compounds; 3) systems including both incongruently and congruently melting compounds. The work was financed by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Chemistry of Wroclaw University of Technology. http://dx.doi.org/10.1016/j.calphad.2015.01.177
[P90] Thermodynamics of carbon trapping at dislocations in martensite Yao V Shan, Walter Mayer, Ernst Kozeschnik
isothermal heating, austenite nucleates and grows. The austenite grains are primarily located at the boundaries of ferrite grains. The simulated microstructure agrees reasonably well with experimental observations. During the continuous cooling process, the austenite-to-ferrite transformation occurs accompanied with carbon diffusion. After cooling from the heating temperature of 760 1C to room temperature with a cooling rate of 2 1C /s, the carbon concentration field is nearly uniform, while a higher cooling rate of 5 1C /s results in a non-uniform carbon concentration field. After tempering at different temperatures for 20 min, the uniformity of carbon distribution increases with increasing tempering temperature. The simulation results are used to understand the mechanisms of the observed experimental phenomena that a cold-rolled low-carbon enameling steel presents different yield strengths after different heat treatment processes. http://dx.doi.org/10.1016/j.calphad.2015.01.179
In this presentation, we introduce a model for carbon trapping at dislocations in martensite. The dislocation sites are treated as part of the BCC_A2 interstitial sublattice, providing energetically favorable atomic positions for carbon. The Gibbs energy of the martensite phase is represented by the thermodynamics of the defect-free and trap-free BCC_A2 lattice, which simultaneously accounts for the contribution from defects. These dislocation sites are described in the framework of a recently developed model for diffusion in systems with multiple traps. In equilibrium, the ratio between the two lattices is entirely determined by the trapping enthalpy between dislocation and carbon and the dislocation density. Our present treatment allows for a general description of the Gibbs energy of martensite, which reproduces the solubility of carbon in relation to the dislocation density as well as the metastable phase equilibria between martensite and Fe-carbides. The model also provides the fundament for future works on kinetic evolution of carbide precipitates in tempering of martensite. http://dx.doi.org/10.1016/j.calphad.2015.01.178
[P91] Thermodynamic and Kinetic Modeling of the Ferrite-Austenite Phase Transformation Dong An, Shiyan Pan, Qing Yu, Chen Lin, Ting Dai, Bruce Krakauer, Mingfang Zhu
A two-dimensional (2D) cellular automaton (CA) model coupled with thermodynamic calculations is proposed to simulate the ferrite-austenite transformation in low-carbon steels. In the model, the driving force for the phase transformation is determined as a function of the difference between the local actual concentration and the equilibrium concentration in ferrite. The local actual concentration is obtained by solving the solute transport equation, while the equilibrium concentration is calculated using the CALPHAD approach. Moreover, the preferential nucleation sites of austenite, solute partition at the ferrite-austenite interface, and carbon diffusion in both the ferrite and austenite phases are taken into consideration. The proposed model is applied to simulate the ferrite-toaustenite transformation during isothermal heating at 760 1C, the austenite-to-ferrite transformation during continuous cooling, and carbon diffusion during tempering at different temperatures for a multi-component steel. The results show that during the
[P92] Phase field study of the growth of intermetallic compounds in multi-component joints Y. Guan, N. Moelans
Hetero-junctions of dissimilar materials are of great importance in daily life. Examples are the integrated and composite material structures used in micro-electronic and photovoltaic devices. One of the main issues in the reliability and life time studies for such integrated material structures is the growth of intermetallic compound (IMC) layers and precipitates at and near the interfaces. The underlying mechanisms of the reactions and microstructure evolution near interfaces in hetero-junctions are however still poorly understood and a general and predictive model is lacking, although extremely important for new technological developments. In this study, a combined modeling approach for the growth of IMCs is derived and implemented based on the phase-field method for microstructure evolution simulations and the CALPHAD method to model phase equilibria and thermodynamic properties in multi-component systems. First-principle calculations are performed to determine the lattice stabilities of the end members of the intermetallic phases, needed for the optimization of a Gibbs energy model with composition dependence. This new simulation method is used, integrated with experimental research, to study the growth of IMCs and their solubility range in Cu-Sn and Ag-Cu-Sn system. http://dx.doi.org/10.1016/j.calphad.2015.01.180
[P93] Microstructure and properties of Cu-Al-Fe high-temperature shape memory alloys Shuiyuan Yang, Yu Su, Cuiping Wang, Xingjun Liu
The microstructure, martensitic transformation, mechanical and shape memory properties of Cu84-xAl11 þ xFe5(x ¼ 0, 1, 2) alloys under the quenched and aged states were investigated. The results show that x ¼ 0 and 1underthe quenched stateexhibita mixture of primary β0 1 and little γ0 1 martensites, and x ¼ 2 only shows
Y. DU et al. / CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry 51 (2015) 344–415
incongruently melting compounds; 3) systems including both incongruently and congruently melting compounds. The work was financed by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Chemistry of Wroclaw University of Technology. http://dx.doi.org/10.1016/j.calphad.2015.01.177
[P90] Thermodynamics of carbon trapping at dislocations in martensite Yao V Shan, Walter Mayer, Ernst Kozeschnik
isothermal heating, austenite nucleates and grows. The austenite grains are primarily located at the boundaries of ferrite grains. The simulated microstructure agrees reasonably well with experimental observations. During the continuous cooling process, the austenite-to-ferrite transformation occurs accompanied with carbon diffusion. After cooling from the heating temperature of 760 1C to room temperature with a cooling rate of 2 1C /s, the carbon concentration field is nearly uniform, while a higher cooling rate of 5 1C /s results in a non-uniform carbon concentration field. After tempering at different temperatures for 20 min, the uniformity of carbon distribution increases with increasing tempering temperature. The simulation results are used to understand the mechanisms of the observed experimental phenomena that a cold-rolled low-carbon enameling steel presents different yield strengths after different heat treatment processes. http://dx.doi.org/10.1016/j.calphad.2015.01.179
In this presentation, we introduce a model for carbon trapping at dislocations in martensite. The dislocation sites are treated as part of the BCC_A2 interstitial sublattice, providing energetically favorable atomic positions for carbon. The Gibbs energy of the martensite phase is represented by the thermodynamics of the defect-free and trap-free BCC_A2 lattice, which simultaneously accounts for the contribution from defects. These dislocation sites are described in the framework of a recently developed model for diffusion in systems with multiple traps. In equilibrium, the ratio between the two lattices is entirely determined by the trapping enthalpy between dislocation and carbon and the dislocation density. Our present treatment allows for a general description of the Gibbs energy of martensite, which reproduces the solubility of carbon in relation to the dislocation density as well as the metastable phase equilibria between martensite and Fe-carbides. The model also provides the fundament for future works on kinetic evolution of carbide precipitates in tempering of martensite. http://dx.doi.org/10.1016/j.calphad.2015.01.178
[P91] Thermodynamic and Kinetic Modeling of the Ferrite-Austenite Phase Transformation Dong An, Shiyan Pan, Qing Yu, Chen Lin, Ting Dai, Bruce Krakauer, Mingfang Zhu
A two-dimensional (2D) cellular automaton (CA) model coupled with thermodynamic calculations is proposed to simulate the ferrite-austenite transformation in low-carbon steels. In the model, the driving force for the phase transformation is determined as a function of the difference between the local actual concentration and the equilibrium concentration in ferrite. The local actual concentration is obtained by solving the solute transport equation, while the equilibrium concentration is calculated using the CALPHAD approach. Moreover, the preferential nucleation sites of austenite, solute partition at the ferrite-austenite interface, and carbon diffusion in both the ferrite and austenite phases are taken into consideration. The proposed model is applied to simulate the ferrite-toaustenite transformation during isothermal heating at 760 1C, the austenite-to-ferrite transformation during continuous cooling, and carbon diffusion during tempering at different temperatures for a multi-component steel. The results show that during the
[P92] Phase field study of the growth of intermetallic compounds in multi-component joints Y. Guan, N. Moelans
Hetero-junctions of dissimilar materials are of great importance in daily life. Examples are the integrated and composite material structures used in micro-electronic and photovoltaic devices. One of the main issues in the reliability and life time studies for such integrated material structures is the growth of intermetallic compound (IMC) layers and precipitates at and near the interfaces. The underlying mechanisms of the reactions and microstructure evolution near interfaces in hetero-junctions are however still poorly understood and a general and predictive model is lacking, although extremely important for new technological developments. In this study, a combined modeling approach for the growth of IMCs is derived and implemented based on the phase-field method for microstructure evolution simulations and the CALPHAD method to model phase equilibria and thermodynamic properties in multi-component systems. First-principle calculations are performed to determine the lattice stabilities of the end members of the intermetallic phases, needed for the optimization of a Gibbs energy model with composition dependence. This new simulation method is used, integrated with experimental research, to study the growth of IMCs and their solubility range in Cu-Sn and Ag-Cu-Sn system. http://dx.doi.org/10.1016/j.calphad.2015.01.180
[P93] Microstructure and properties of Cu-Al-Fe high-temperature shape memory alloys Shuiyuan Yang, Yu Su, Cuiping Wang, Xingjun Liu
The microstructure, martensitic transformation, mechanical and shape memory properties of Cu84-xAl11 þ xFe5(x ¼ 0, 1, 2) alloys under the quenched and aged states were investigated. The results show that x ¼ 0 and 1underthe quenched stateexhibita mixture of primary β0 1 and little γ0 1 martensites, and x ¼ 2 only shows