• Inverse-problem approach using stress–strain curve (SS curve) of TRIP steel • Estimating SS curves of γ and deformation-induced α’ phases during tensile testing • Estimating change in volume fraction of α’ phase during tensile testing • Enabling us to analyze stress partitioning between γ and α’ phases An inverse-problem approach is proposed wherein a computational model of the stress–strain (SS) curve of a two-phase composite material is fitted to experimental data on the SS curve of metastable austenitic stainless steel for estimating the SS curves of individual phases of fcc-γ and deformation-induced bcc-α’, as well as the change in the volume fraction of the α’ phase ( f (α′) ) with increasing strain. The proposed method was applied to the SS curves of two types of TRIP steels: Fe–18Cr–8Ni–0.1C (mass%) alloy (0.1C steel) and Fe–18Cr–8Ni–0.1N (mass%) alloy (0.1N steel). The SS curves of individual phases (γ and α’) were estimated to reproduce the overall SS curve of TRIP steel reported in a literature. The estimated flow stress of the α’ phase for 0.1C steel significantly exceeded that for 0.1N steel, indicating that carbon addition is more effective than nitrogen addition in strengthening the deformation-induced α’ phase. Additionally, the proposed method allowed us to examine the phase stress (stress partitioning between the γ and α’ phases) during tensile deformation. Further, the change in f (α′) during tensile deformation was estimated, and the results closely matched the experimental data from the literature. The increase rate of f (α′) in 0.1C steel is lower than that in 0.1N steel, which is essential information for optimizing the strength–ductility balance of TRIP steel.
Kawamoto et al. (Sun,) studied this question.