Influence of precooling and deformation temperature on microstructure and mechanical properties in a high-manganese austenitic steel

In this work, the influence of precooling on deformation-induced α′-martensitic transformation and mechanical properties of Fe–16Mn–4Cr–0.1C (wt%) austenitic steel is investigated. It is shown that precooling in liquid nitrogen enhances the volume fraction of ε-martensite. During tensile testing, ε-martensite acts as a nucleation site for α′-martensite and promotes the strength and ductility of the steel. The precooled steel exhibits an excellent combination of mechanical properties (tensile strength of 1240 MPa, uniform elongation of 35% and total elongation of 42%). Further, it is shown that tensile strength and elongation of the steel strongly depend on the deformation temperature. This is explained by the influence of temperature on stacking fault energy (SFE) and accordingly governing deformation mechanisms of the steel.