Review of Shape Memory Alloys: Fundamental, Microstructure Property, and Emerging Trends in Industrial Applications

Shape Memory Alloys (SMAs) are an exceptional category of functional materials that can restore predefined shapes or sustain substantial reversible deformations through thermoelastic martensitic transformations.In recent years, SMAs have attracted significant interest due to their unique combination of mechanical adaptability, durability, and multifunctionality, making them highly relevant for advanced engineering applications.This review provides a detailed examination of SMAs, including their classification into Ni, Cu, Febased, and emerging high-entropy alloy (HEA) systems, as well as a historical perspective on the development of the Shape Memory Effect (SME) and Superelasticity (SE).The discussion addresses critical factors influencing SMA performance, such as alloy chemistry, microstructural characteristics, processing techniques, quenching and homogenization treatments, and transformation temperatures (M , Mf, As, Af).Applications are explored with a focus on NiTi alloys in biomedical devices and precision actuators, Fe-Mn-Si for structural use, and Cu-Zn-Al for energy-efficient and cryogenic applications.Emerging directions, including soft robotics, thermal energy devices, and architected SMA structures enabled by additive manufacturing, are reviewed, along with strategies to mitigate issues such as cyclic degradation, hysteresis, and reliability concerns.By integrating theoretical insights with practical considerations, this review highlights the growing industrial relevance of SMAs as versatile, high-performance materials for next-generation adaptive systems.