Couplings between plasticity and martensitic phase transformation: overallbehavior of polycrystalline TRIP steels

Several couplings between plasticity and martensitic phase transformation a re at the origin of remarkable proper tics of ductility and toughness in th e case of TRIP steels, A micromechanical model is developed to predict the conditions of nucleation and growth of a martensitic microdomain inside an inhomogeneous plastic strain field. More explicit relations are developed i n the case of a simple shear test where a heterogeneous plastic strain held leads to a significant decrease of the critical stress for martensitic tra nsformation. The obtained results are combined with a kinetics and kinemati cs studies to derive the constitutive equation of an austenitic single crys tal from which the overall behavior of a polycrystalline steel is deduced u sing the self-consistent scale transition method. Comparison with experimen tal data shows a good agreemcnt. (C) 2000 Published by Elsevier Science Ltd .