Uniform Formation of Fine Grained Ferrite Structure through Multi-directional Deformation

Abstract

A multi-directional deformation thermo-mechanical treatment simulator was designed and developed to verify the prediction by the FE-analysis on the effect of bi-directional deformation which can introduce a large plastic strain widely in a specimen. Using this simulator, both uni-directional and bi-directional deformations were performed for a 0.16%C-0.4%Si-1.4%Mn steel with a prior austenite grain size of 300 μm at 1073K at a strain rate of 1/s. The microstructure was composed of polygonal ferrite and intragranular Widmanstätten ferrite in the uni-directional deformation specimen. On the other hand, the half thickness of the specimen was composed of fine polygonal ferrite in the bi-directional deformation specimen. This region corresponds well to the region having a plastic strain of more than 2. The uniform formation of the fine polygonal ferrite due to the wide introduction of the large plastic strain was verified for the bi-directional deformation.