Numerical investigation of the interaction between the martensitic transformation front and the plastic strain in austenite

Phase-field simulations of the martensitic transformation (MT) in the austenitic matrix, which has already undergone the plastic deformation, are carried out. For this purpose the elasto-plastic phase-field approach of incoherent MT developed in the previous work [Kundin et. al. J. Mech. and Phys. Solids 59 (2011) 2012] is used. The evolution equation for the dislocation density field is extended by taking into account the thermal and athermal annihilation of the dislocations in the austenitic matrix and the athermal annihilation at the transformation front. It is shown that the plastic deformation in the austenite caused by the MT interacts with the pre-deformed plastic strain that leads to the inhomogeneous increasing of the total dislocation density. During the phase transformation one part of the dislocations in the pre-deformed austenite is inherited by the martensitic phase and this inheritance depends on the crystallography of MT. An other part of dislocations annihilates at the transformation front and decreases the dislocation density in the growing martensite. Based on the simulation results a phenomenological dependency of the inherited dislocations on the martensitic fraction and the plastic deformation in the martensite and austenitic matrix is proposed.