A microstructure-based analysis for transformation induced plasticity and mechanically induced martensitic transformation

The transformation-induced plasticity (TRIP) accompanying the mechanically induced martensitic transformation (MIMT) in metastable austenitic steel was analyzed with a microstructure-based computational model which takes into account void nucleation and growth. The kinetics of the martensitic transformation was modeled using the concept of variant selection, which considers that the probability of nucleation occurring at a given site can be derived for each martensitic variant as a function of the interaction energy between the externally applied stress state and the lattice deformation based on the Kurdjumov-Sachs (K-S) orientation relationship. To consider the localization of the plastic flow in the deforming material, the increase in void nucleation due to the martensitic transformation and the void growth based on the Gurson-Tvergaard yield criterion were adopted. The plastic instability condition was employed to predict the ductility of metastable austenitic steel. The calculated results were compared with the experimental data measured for 301 stainless steel subjected to uniaxial tension. The major cause of the enhancement of the ductility in the TRIP-aided steel was discussed from the viewpoint of the effect of the TRIP strain and the phase-hardening due to the MIMT. In addition, the evolution of the crystallographic texture during deformation and phase transformation was predicted by using the combination of the proposed model and the crystal plasticity.