Multi-scale in situ characterization of micro-deformation during Lders band propagation in a medium Mn steel

中Mn鋼のリューダースバンド伝搬に伴う微小変形のマルチスケールその場観察

小山 元道*; 山下 享介*; 諸岡 聡  ; Yang, Z.*; Varanasi, R.*; 北條 智彦*; 川崎 卓郎   ; Harjo, S.   

Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Yang, Z.*; Varanasi, R.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.

The micro-deformation of an Fe-5Mn-0.1C medium Mn steel consisting of face-centered cubic and body-centered cubic phases was characterized through multi-scale in situ scanning electron microscopy. Specifically, multiscale in situ back-scatter electron imaging coupled with ex situ electron backscatter diffraction measurements was conducted under tensile testing. The Fe-Mn-C alloy showed macroscopically localized deformation (i.e., Lders deformation), and the deformation-localized region consisted of multiple find deformation bands. The hierarchical structure of the deformation bands initiated from a specimen side edge and propagated to the other side edge. More microscopically, the plastic deformation preferentially progressed in a face-centered cubic phase, and temporarily stopped when the fine deformation band encountered a group of body-centered cubic grains, which resulted in zigzag propagation of the fine deformation bands. Through coalescence of fine deformation bands, a thick macroscopic deformation band formed. By repetition of the micro-deformation process, the thick deformation band front moved along the tensile direction from an end of the gauge portion to the other end.