Microscale investigation of phase transformation and plasticity in multi-crystalline shape memory alloy using discrete dislocation-transformation method

Martensitic phase transformation and plasticity are two primary mechanisms of deformation in shape memory alloys (SMAs) and the interaction between them influences the behaviour of SMA during cyclic loading, specifically the pseudoelasticity behaviour and the shape memory effect. This interaction, which occurs in microscale, affects the reversibility and eventually the actuation capacity of SMAs. In order to capture this interaction in microscale, a discrete dislocation-transformation model was developed in Sakhaei et al. (Mech Mater 97:1-18, 2016) and was applied to simulate the single-crystalline NiTi samples under thermo-mechanical loads. In this study, the microscale coupling between phase transformation and plasticity as well as grain size and orientation effects is investigated in multi-crystalline shape memory alloys under thermal and mechanical loading by using the discrete dislocation-transformation framework through the representative numerical simulations. The results illustrated the dependency of dislocation slip and martensitic transformation to crystalline orientations as well as grain size and grain boundary densities in the multi-crystalline SMAs.