Heat treatment effects on the microstructure and mechanical properties of a medium manganese steel (0.2C-5Mn)

► Substantially improved mechanical properties of 0.2C-5Mn steels. ► Intercritical austenization followed by short time annealing. ► Phase transformation induced plasticity of the large volume fractioned austenite. ► Dependence of yield stress on austenite grain size accords with Hall-Petch equation.