Metallurgical and materials transactions a-physical metallurgy and materials science vol:37A issue:1 pages:99-107
A three-dimensional finite-element microstructural cell model involving an inclusion of retained austenite embedded within a ferrite grain, which is surrounded by a homogeneous matrix representing the behavior of a transformation-induced-plasticity (TRIP)-assisted multiphase steel, was developed in order to address the micromechanics of the martensitic transformation in small isolated austenite grains. The transformation of a single martensite plate is simulated after various amounts of prior plastic deformation under different in-plane loading conditions. The values of the mechanical driving force and of the elastic and plastic accommodation energies associated with the transformation are calculated as a function of the externally applied loading conditions. The mechanical driving force and the total accommodation energy are of the same order of magnitude. The mechanical driving force depends upon the stress state and is the highest for plane-strain conditions. The total accommodation energy is almost independent of the stress state. It is affected by the amount of plastic straining prior to transformation and is very much dependent on the level of the shear component of the transformation strain. The results of this study provide guidelines for the development of realistic stress-state-dependent transformation evolution laws for TRIP-assisted multiphase steels.