Hierarchical deformation heterogeneity during Lders band propagation in an Fe-5Mn-0.1C medium Mn steel clarified through scanning electron microscopy

その場走査型電子顕微鏡によるFe-5Mn-0.1C中Mn鋼のリューダースバンド伝搬に伴う階層的変形不均一性の解明

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

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

deformation experiments with cold-rolled and intercritically annealed Fe-5Mn-0.1C steel were carried out at ambient temperature to characterize the deformation heterogeneity during Lders band propagation. Deformation band formation, which is a precursor phenomenon of Lders band propagation, occurred even in the macroscopically elastic deformation stage. The deformation bands in the Lders front grew from both the side edges to the center of the specimen. After macroscopic yielding, the thin deformation bands grew via band branching, thickening, multiple band initiation, and their coalescence, the behavior of which was heterogeneous. Thick deformation bands formed irregularly in front of the region where the thin deformation bands were densified. The thin deformation bands were not further densified when the spacing of the bands was below 10 m. Instead, the regions between the deformation bands showed a homogeneous plasticity evolution. The growth of the thin deformation bands was discontinuous, which may be due to the presence of ferrite groups in the propagation path of the deformation bands. Based on these observations, a model for discontinuous Lders band propagation has been proposed.