Dislocation interaction and twinning-induced plasticity in face-centered cubic Fe-Mn-C micro-pillars

Abstract

Deformation twinning contributes to a high work-hardening rate through modification of the dislocation structure and a dynamic Hall-Petch effect in polycrystalline steel. Due to the well-defined compression axis and limited deformation volume of micro-pillars, micro-compression testing is a suitable method to investigate the mechanisms of deformation twinning and the interactions of dislocations with twin boundaries. The material investigated is an austenitic Fe-22 wt%Mn-0.6 wt%C twining-induced plasticity steel. Micro-pillars oriented preferentially for deformation twinning and dislocation glide are compressed and the activated deformation systems are characterized. We observe that deformation twinning induces higher flow stresses and a more unstable work-hardening behavior than dislocation glide, while dislocation glide dominated deformation results in a stable work-hardening behavior. The higher flow stresses and unstable work-hardening behavior in micro-pillars oriented for deformation twinning are assumed to be caused by the activation of secondary slip systems and accumulated plastic deformation. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.