In situ crystallographic observation of dynamic ferrite transformation evolution during hot deformation of low alloy steels

Xu, P. G.   ; Tomota, Yo*; Koo, M.*; Yonemura, Masao*; Suzuki, Tetsuya*; Paradowska, A.*; Zhang, S. Y.*; Adachi, Yoshitaka*

Deformation induced ferrite transformation related to microstructure refinement has attracted wide attention. However, the in situ crystallographic evolution studies have not been carried out. In this paper, the deformation induced ferrite transformation at two different strain rates was carried out to compare that during isothermal holding without deformation and the effects of hot deformation and strain rate on the dynamic transformation evolution was investigated. The neutron diffraction experiments confirmed that the deformation induced ferrite transformations could appear not only in the austenite region, but also in the austenite-ferrite dual phase region. It was found that the low temperature deformation was more effective than the high temperature to promote the ferrite transformation until a critical strain, and then the accelerating effect was weakened due to the increment of austenite carbon concentration and the appearance of ferrite dynamic recrystallization.