Different Effects of Ni and Mn on Thermodynamic and Mechanical Stabilities in Cr-Ni-Mn Austenitic Steels

Thermodynamic and mechanical stabilities of austenite were investigated in Cr-Ni-Mn austenitic steels by varying the contents of Ni and Mn. Mn was more beneficial to increasing thermodynamic stability against martensitic transformation than the equivalent amount of Ni. However, the tendency for strain-induced martensite transformation was governed not by the thermodynamic stability but by stacking fault energy (SFE) which was increased more effectively by Ni than by the equivalent amount of Mn. A modified SFE equation and experimentally determined Ni equivalents may suggest a criterion for austenite stability throughout tensile deformation.