Austenite stability and deformation-induced transformation mechanism in cold-rolled medium-Mn steel

The austenite stability and tensile properties of intercritically annealed samples of cold-rolled medium-Mn steel (0.15C–5Mn-1.1Al) were investigated. The influence of austenite grain size and element concentration on the mechanical stability of austenite was studied, which demonstrated that the C content in austenite was a critical factor governing the mechanical stability of austenite. The thermal stability of austenite in cold-rolled medium-Mn steel samples annealed for different durations at different temperatures was quantitatively analyzed. The results showed that the effect of annealing temperature on the thermal stability of austenite was stronger than that of annealing time. In addition, the samples subjected to heat treatment under different conditions resulted in different work hardening (WH) behavior and mechanical properties due to variations in the mechanical stability of the retained austenite. It was concluded that these differences were related to the changes in stress- and strain-induced transformation modes of the retained austenite.