Formation mechanism of the eye-shaped nano-twin bundles in cold rolled 316L stainless steel

Abstract

The microstructural evolution of a typical coarse-grained 316L stainless steel was explored with the rolling reduction changed from 0% to 80%. The formation mechanism of the novel eye-shaped nano-twin (NT) bundles was clearly revealed. The results show that numerous dislocations were propagated and accumulated around original grain/annealing-twin boundaries at low rolling strain level (20%), which led to a high stress concentration and induced the generation of deformation twin bundles. With the rolling reduction increase to 40%, the number of deformation twin bundles increased and the average thickness of deformation twins decreased. In addition, some micro shear bands were motivated to cut the deformation twin bundles, resulting in the formation of eye-shaped deformation twin bundles. With the further increase of the rolling reduction (60–80%), the average thickness of deformation twins was decreased to nano-scale. Many eye-shaped NT bundles were formed by the cutting activity from the micro shear bands.