Shape memory alloys (SMAs) exhibit thermoelastic martensitic transformation, a diffusionless reversible solid-state phase change between a high-temperature high-symmetry cubic austenite phase and a low-temperature lower-symmetry twinned martensite phase. Upon mechanical loading, twinned martensite easily detwins to accommodate large strains; subsequent heating above the austenite finish temperature (A_f) fully restores the original parent shape.