Heterogeneous Structure-Induced Excellent Functional Properties in Shape Memory Alloys: A Review

In structural materials, architecting a heterogeneous structure has been proven an effective strategy to achieve extraordinary comprehensive mechanical properties, such as combining high strength, excellent fatigue resistance, high ductility, etc. Improvement of mechanical properties is also a constant pursuit of metallic functional materials of shape memory alloys (SMAs), which is the precondition for realizing associated functional responses. The microstructural heterogeneity of SMAs plays a critical role in resisting irreversible deformation and regulating the nature of thermoelastic martensitic transformation. In this review, we focus on the recent progress of SMAs reinforced by heterogeneous microstructure spanning various length scales, which incorporates favorable mechanical and functional properties under external stimuli. These results point to an intriguing future in which novel and specific functionality of SMAs can be triggered programmatically by building a hierarchy of microstructures. © 2023, The Minerals, Metals & Materials Society.