Temperature Dependency of Diffusional Transformation Texture Development in Steel Sheet

Abstract

The temperature dependency of diffusional transformation texture development in steel sheet was investigated by electron backscatter diffraction. The site of the precipitated pro-eutectoid ferrite (PF) grains and the orientation relation with the surrounding austenite (γ) phase were affected by the transformation temperature. The PF on the triple junction, which has a Kurdjumov-Sachs relation (K-S) with the two surrounding γ phases (double K-S [DKS] relation) with high probability, predominated in the high-temperature transformation, whereas the PF on the grain boundary, which fulfills DKS with lower probability than the PF on triple junction, became predominant with decreasing temperature. The intensity of the variant selection on transformation decreased with decreasing transformation temperature. The texture predicted by the DKS model reproduced the measured PF texture, indicating that the intensity of the variant selection obeying DKS decreased with decreasing transformation temperature. Therefore, the intensity of the variant selection was affected by the degree of supercooling. The DKS rule operates strongly on the transformation in the high-temperature region, corresponding to a low degree of supercooling. However, the DKS rule has a small effect when the temperature decrease corresponds to a high degree of supercooling.