Deformation rate controls atomic-scale dynamic strain aging and phase transformation in high Mn TRIP steels

Abstract

Dynamic strain aging (DSA) in engineering metallic alloys triggers a degradation of the relevant properties of these material. Atomic-scale understanding of DSA is essential for achieving strong and ductile high-Mn martensitic-austenitic transformation induced plasticity (TRIP) steels. Using multiple-scale analytical techniques, we report the influence of carbon addition and strain rates on the mechanical properties and associated deformation-induced phase transformation of these steels. Specific attention is also placed on the origin of DSA at the atomic scale. We find that controlling these parameters (carbon and strain rate) can be used to manipulate the room temperature reverse transformation from martensite to austenite, plastic instability, short-range ordering (SRO), TRIP effect, and strain hardening of these steels. Thus, our results demonstrate that the SRO caused by short-range clustering (SRC) is linked to the DSA, and that high-strain-rate deformation induces an increase in the carbon concentration of SRC, leading to the DSA suppression. Hence, we suggest that manipulating phase transformation and DSA is utilized to achieve strong and ductile steels with continuous and stable flow. ? 2017 Acta Materialia Inc.