Overcoming plasticity reduction in a severely deformed nano-grained metastable alloy

Generally, most bulk metallic materials reveal an increased strength but a loss of ductility after cold deformation, referred as the strength–ductility trade-off. This phenomenon is moderately less in some metastable alloys, which exhibit a transformation-induced plasticity (TRIP), i.e., a martensitic transformation from FCC phase to BCC phase. However, most of them show outstanding mechanical properties induced by TRIP effect only at cryogenic conditions. In this study, we present a strategy to overcome this problem by introducing a high density of crystalline defects into a Fe-based metastable alloy by refining grains to a nanometer scale. This procedure significantly improves the kinetics and reduces the driving force for TRIP. As a result, the TRIP effect originally occurring at cryogenic temperature in the Fe-based metastable alloy, is also active at ambient conditions, contributing to a strength-ductility synergy and overcoming cold working induced sacrifice of ductility.