Nature of dynamic ferrite transformation revealed by neutron diffraction analysis during thermomechanical processing

加工熱処理中のその場中性子回折分析によって明らかにされた動的フェライト変態の性質

柴田 曉伸*; 竹田 泰成*; Park, N.*; Zhao, L.*; Harjo, S.   ; 川崎 卓郎   ; Gong, W.*; 辻 伸泰*

Shibata, Akinobu*; Takeda, Yasunari*; Park, N.*; Zhao, L.*; Harjo, S.; Kawasaki, Takuro; Gong, W.*; Tsuji, Nobuhiro*

Nowadays, a new concept of process utilizing dynamic ferrite transformation, which can achieve ultrafine-grained structure with a mean grain size of approximately 1m, has been proposed. This paper reports transformation mode of dynamic ferrite transformation and formation mechanism of ultrafine-grained structure revealed by our novel technique of neutron diffraction analysis during thermomechanical processing. Dynamic ferrite transformation occurs in a diffusional manner, whose partitioning behavior changes from para- to ortho-equilibrium with the progress of transformation. Moreover, we propose that dynamic recrystallization of dynamically-transformed ferrite is the main mechanism for the formation of ultrafine-grained structure.