2016 Volume 57 Issue 9 Pages 1514-1519
The crystal orientation of nucleating austenite during reverse phase transformation of a C-Mn steel has been investigated by in situ EBSD technique using a heating stage of FE-SEM at temperatures ranging from RT to 800℃. It has been found that the multiple interfaces between a nucleating austenite grain and the surrounding parent ferrite grains are preferentially selected as the Kurdjumov-Sachs (K-S) relationship. More than 50% of austenite grains are surrounded with two or more parent ferrite grains satisfying the K-S relationship with a deviation within 7°. Based on these findings, a nucleation model at triple junction is proposed, which supposes that the orientation of nucleating austenite is selected to satisfy the K-S relationship or the orientation relationship close to K-S relationship at two of the interfaces to ferrite grains, and at the other interfaces to minimize the misorientation from the K-S relationship.