Size and orientation effects in partial dislocation-mediated deformation of twinning-induced plasticity steel micro-pillars

Abstract

Bulk and micro-pillar single crystals were used to investigate the twinning-induced plasticity mechanism in austenitic Fe-22 wt%Mn-0.6 wt%C TWIP steel. Compression of micro-pillars oriented either for deformation-induced twinning or for perfect dislocation glide was carried out for pillars with diameters in the range of 600 nm to 4 mu m. The same size dependence of the critical resolved shear stress was observed for both orientations. The critical micro-pillar diameter for size-independent plasticity was approximately 7.6 mu m. Partial dislocation-mediated formation of twins and epsilon-martensite was observed in micro-pillars oriented for twinning by transmission electron microscopy. The elastic-plastic transition in micro-pillars oriented for deformation twinning did not involve twinning, and dislocation-dislocation interactions were a necessary precondition for twin formation. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.