Kinetics of strain-induced transformation of dispersed austenite in low-alloy TRIP steels

A model describing the kinetics of the evolution of martensite volume fraction during the strain-induced transformation of dispersed austenite in low-alloy TRIP steels has been developed. The model is based on the modification of the nucleation site potency distribution by the applied stress and plastic strain for the description of the stress-assisted and strain-induced transformation regimes respectively. The model is fitted to available experimental data regarding the evolution of martensite as a function of plastic strain for several steels containing austenitic dispersions. Besides chemical composition of retained austenite and temperature, the model takes into account the effects of austenite particle size and stress triaxiality. Austenite particle size refinement has a strong stabilizing influence by retarding the strain-induced transformation kinetics. Stress triaxiality becomes important in stabilized austenite dispersions (either chemically stabilized or by size refinement) by enhancing the kinetics of the strain-induced transformation. The kinetic model can be used for the development of a constitutive model describing the mechanical behavior of TRIP steels.