Phase engineering and supercompatibility of shape memory alloys

In recent years examples of unprecedented functional and structural fatigue resistance and lowered hysteresis in shape memory alloys have been achieved by combining conditions of supercompatibility between phases with suitable grain size and a favorable array of fine precipitates. We collect, review and compare these examples to elucidate the relative roles of these factors, especially in the case of the more demanding stress-induced phase transformations, and we pose key open questions. The control of these factors lends itself to systematic alloy development. Taken together, these results point to significant opportunities to discover improved shape memory alloys as well has new reversible transforming multiferroics.