Design of alloy composition in 5%Mn-Cr-C austenitic steels

The range of chemical compositions that can obtain an austenitic single structure was defined for medium-manganese (Mn) carbon (C) steels. Among the potential compositions, Fe-5%Mn-4%Cr-(0.8-1.4)%C (mass%) was selected as the optimized composition range to form a stable austenitic structure. The tensile properties and deformation substructure were investigated in the austenitic steels having this composition. The work hardening behavior of the steels varied depending on the carbon content, which was closely related to the deformation microstructure. In the 0.8%C steel, both a deformation-induced martensitic phase as well as the formation of deformation twins generated a high work hardening until fracture. With an increasing carbon content, which increased the stacking fault energy (SFE), the deformation tended to shift towards dislocation slipping, resulting in a lower work hardening rate. This trend appears similar to conventional twinning-induced plasticity steel where the work hardening behavior is tied to the SFE.