Role of Deformation-Induced Martensite in TRIP Effect of Metastable Austenitic Steels

Abstract

Role of deformation-induced martensite in the transformation-induced plasticity (TRIP) of metastable austenitic steels was studied by examining effects of temperature on the tensile properties of Fe–18%Cr–6%Ni–0.2%N–0.1%C (6Ni–0.2N–0.1C) steel. The tensile properties obtained by tensile tests at various temperatures between 123 and 373 K were compared with those of SUS304 steel. The 0.2% proof stress, tensile strength, and uniform elongation of the 6Ni–0.2N–0.1C steel were larger than those of SUS304 at all temperature studied, and the mechanical stability of the austenite for the 6Ni–0.2N–0.1C steel was higher than that for the SUS304 steel. Neutron diffraction experiments at room temperature showed that the improvements in the mechanical properties in the 6Ni–0.2N–0.1C steel were associated with larger work hardening of the austenite and larger strength of the deformation-induced martensite. The increase in strength of deformation-induced martensite with N and C additions leads to better mechanical properties due to the TRIP effect, despite of smaller amounts of deformation-induced martensitic transformation.