Effect of Nitrogen on Deformation-Induced Martensitic Transformation in an Austenitic 301 Stainless Steels

The effect of nitrogen on deformation-induced martensitic transformation (DIMT) in metastable 301 austenitic stainless steel has been studied based on the inelastic deformation theory. DIMT is regarded here as continuous relaxation process of internal strain energy accumulated during inelastic deformation. Using the kinetics equation based on the inelastic deformation theory the relationship between the volume fraction of transformed martensite and inelastic strain for DIMT has been successfully verified with the parameter representing the stability of austenite. The addition of nitrogen is experimentally found to increase austenite stability and the critical inelastic strain below which any DIMT is not observed to occur and to decrease the saturation volume fraction of α’ martensite. On the other hand, DIMT has been analyzed with its effect on stress-strain curve shape and mechanical properties in relation to the addition of nitrogen. The characteristic transition from sigmoidal to parabolic curve shape in stress-strain response has disappeared with the addition of nitrogen