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

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

Scripta Materialia, 165, p.44 - 49, 2019/05

https://doi.org/10.1016/j.scriptamat.2019.02.017

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.