Phase-field法によるFe-C合金のγ→α変態と炭素拡散挙動の評価

抄録

Numerical simulations are performed to investigate the austenite-to-ferrite transformation in Fe-C alloy by employing a phase-field method, which can simultaneously simulate both interface migration and carbon diffusion without complex tracking of the interface position. The effects of transformation temperature and initial carbon concentration in austenite on the transformation behavior are investigated in detail as a one-dimensional problem. Simulation results show that the transformation kinetics varies between diffusion-controlled mode and interface-controlled mode depending on the temperature and carbon concentration. Therefore, the local equilibrium condition is not satisfied at the interface during the interface migration, while carbon concentration at the interface in austenite increases as the ferrite phase grows. Furthermore, we have evaluated the critical composition in which interface-controlled transformation occurs in the temperature range from 873 K to 673 K. It is clarified that the interface-controlled transformation cannot occur in the two phase region below 723 K.