Modelling the interaction between plasticity and the austenite-martensite transformation

Many advanced steels, such as high strength steels and TRIP steels, owe their excellent combination of strength and ductility to the complex microstructural behaviour involving the austenite to martensite phase transformation. In this paper a physically-based model for martensitic transformation induced plasticity at the grain level is presented. In terms of output, the model provides the evolution of the overall martensite volume fraction within a grain and the overall stress-strain response of a grain, as well as the martensite volume fractions produced on each of the potential transformation systems. The model directly incorporates the coupling between elasticity, plasticity, plastic history inheritance and transformation. In this work, special attention is given to a proper incorporation of the interaction between the plastic deformation of austenite and the martensitic transformation, which is known to be twofold. On one hand, the plastic deformation of austenite is known to promote the transformation by creation of additional nucleation sites for the transformation, on the other hand the dislocation foresting leads to the mechanical stabilization of austenite, thus retarding the transformation. These two effects are incorporated in the model. To illustrate the performance of the model it has been applied to the deformation and transformation of a single austenitic grain loaded in different crystallographic directions, focusing on the transformation after the plastic prestraining of austenite.