Variant Selection in Phase Transformation and its Influence on Texture and Martensite Starting Temperature in Steel

A mechanism is proposed that can predict the textures as well as the influence of austenite grain size on martensite starting temperature in steels. The anisotropic elastic energy by shape change of martensite changes depending upon variants in neighbour austenite grains, whereas it does not in immediate parent grains in which martensite grows. A mechanism based on this behaviour of elastic energy can explain not only the texture formation of martensite but also the well-known austenite grain size dependence of Ms, particularly the abrupt drop of about 30K in the grain size range below 20 μm.