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

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.

Automated summary

This study found that the tensile properties of 6Ni-0.2N-0.1C steel were superior to those of SUS304 steel at different temperatures, mainly due to the significant strengthening effect of deformation-induced martensite, resulting in improved mechanical properties of the austenite.