Modeling of twinning-induced plasticity using crystal plasticity and thermodynamic framework

Abstract

In many applications of steels, especially in aerospace and petroleum industry, large deformation is required in order to achieve complex shape and geometry of finished products. In these, advanced high-strength steels play a vital role by attaining favorable amalgamation of high strength and ductility. Among all second-generation steels, twinning-induced plasticity contains a significant percentage of austenite phase, shows outstanding tensile strength and ductility. The primary cause of having these outstanding properties is found to be stress-assisted austenite to martensite phase transformation, commonly described as twinning. In this paper, a micromechanical model is developed in the thermomechanical framework to investigate elastic–plastic deformation of twinning-induced plasticity steel. It is assumed that plastic deformation is caused due to slip and mechanical twinning under given loading conditions. Firstly, a micromechanical constitutive model, considering slip and mechanical twinning as sources of permanent deformation, is developed by kinematic decomposition of an austenite crystal into intermediate configurations. Secondly, a thermodynamic framework is used to formulate driving potentials for slip and twinning mechanisms. Thirdly, the developed model is numerically implemented into finite element software ABAQUS by a user-defined material subroutine. Finally, the deformation behavior of single and polycrystalline austenite are predicted by numerical simulations in tension compression, and simple shear loading conditions. It is found that in tension twin deformation plays a dominant role, while the reverse is observed in compression. In simple shear, on an activation of twin mode, slip systems encounter higher slip resistance due to slip–slip and slip–twin interactions.