(S151)Development of Fe-C potential and analysis of martensitic transformation in carbon steel

摘要

Interstitial carbon atoms have various effects on formation of microstructures in steels. In martensitic transformation, carbon stabilizes austenite and lowers Ms temperature significantly. Although this phenomenon is thermodynamically explained in terms of Gibbs free energy change due to carbon addition to austenite, the atomic scale role of carbon in martensitic transformation is not necessarily clarified. As one of the factors influencing on the austenite stabilization, solid solution strengthening of austenite matrix is considered to play an important role; however, there is no evidence of the carbon effect to retard dislocation motion or interface migration during martensitic transformation, because the diffusionless transformation is very fast and difficult to observe it experimentally. Recently, the fcc-bcc phase transformation kinetics of iron was studied by molecular dynamics simulations using Finnis-Sinclair (FS) potential, where the bcc phase grew in needle-like morphology from fee phase with K-S relationship [1]. We thought the effect of carbon on the martensite transformation could be analyzed if we used the interatomic potential for the Fe-C interaction. So, we developed FS potential for the Fe-C interaction and calculated the interaction between carbon and phase interface.