Simulation of mechanical behavior of multiphase TRIP steel taking account of transformation-induced plasticity

Due to the effect of transformation-induced plasticity, multiphase low alloy TRIP steel exhibits an enhanced combination of strength and ductility. Moreover, volume fractions of the constituents in TRIP steel vary during its plastic deformation. In this paper, a constitutive model for mechanical behavior of multiphase TRIP steel is presented. In the model, TRIP steel microstructure is decomposed into four individual constituents: austenite, martensite, bainitic ferrite and ferrite. Mechanical behavior of each individual phase is described by using physically-based model. On the basis of introducing transformation-induced plasticity (TRIP) strain into decomposition of total strain, stress–strain relation of multiphase composite is obtained by using mixture rule and Iso-W hypothesis. Kinetics of strain-induced martensitic transformation is described by a generalized form of Olson–Cohen model, which takes into account temperature and stress state. Moreover, a new method to describe evolving grain size of retained austenite due to martensitic transformation is developed. On the basis of presented model, mechanical behavior of multiphase steel is simulated by using finite element method. Parameters of the model are calibrated for different mixture laws used in calculation. The simulated results have a good agreement with those observed in experiments.