Micro-plasticity of medium Mn austenitic steel: Perfect dislocation plasticity and deformation twinning

The micro-scale plastic deformation behavior of an austenitic Fe-1.2%C-7.0%Mn (in wt%) steel was studied by means of nano-indentation and in situ compression of micro-pillars with selected crystallographic orientations. Transmission electron microscopy analysis reveals that the partial dislocation mediated twinning is preferred in a [001]-oriented single grain under compression. Twinning leads to large strain bursts during the nano-indentation and the micro-pillar compression. Perfect dislocation slip is the dominant deformation mechanism in a [111]-oriented single grain under compression. The observations offer strong support for the hypothesis that deformation twinning is a plasticity enhancing mechanism activated during the deformation of medium Mn steel. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.114sciescopu