Deformation physics of shape memory alloys – Fundamentals at atomistic frontier

Application spectrum of shape memory alloys (SMA) is expanding rapidly and proportionately so is the engineering demand for superior materials. An essential prerequisite to developing novel SMAs is a clear perception of the deformation physics underlying their extraordinary shape recoverability. To that end, modern atomistic simulation tools have proffered state-of-the-art models, which usher in new clarifications for SMA deformation properties. It was found, for example, that ab initio energy pathways are at the core of dictating the extent of shear and shuffle for both phase transformation and variant formation at atomic lengthscale. These important revelations are accomplished by addressing inherent solid-state effects, which underpin the natural tendency to seek the energetic ground state. Moreover, empirical potential based models, benefitting from ab initio calculations, have allowed an atomic-resolution view into the phase evolution and the concurrent twinning phenomena relating directly to constitutive properties. Here, we revisit salient examples of these cutting-edge theoretical discoveries regarding SMA deformation along with discussions on pertinent experimental evidences.