High-entropy shape-memory alloys (HESMAs) exhibit unique properties, including high yield strength, a wide temperature range of phase transformation, and excellent thermal cycling stability, among others. Hence, they have broad prospects for research and application. Currently, various new high-entropy shape-memory alloys have been developed based on TiNi, Fe-based, Ti-based, and NiMn-based alloys. This article focuses on summarizing and analyzing the research status of various types of high-entropy shape-memory alloys, including their microstructure characteristics, martensitic phase transformation, and functional properties. The advantages and disadvantages of high-entropy shape-memory alloys compared to traditional shape-memory alloys are briefly discussed. Finally, based on the analysis of existing problems, future research prospects are proposed, hoping to provide assistance for the development and application of high-entropy shape-memory alloys in the future.

Multiple martensitic transformation peaks were observed from differential scanning calorimetry curves in aged ${\mathrm{Mn}}_{50}{\mathrm{Ni}}_{25}{\mathrm{Ga}}_{25}$ alloys in which transformation temperature varied with aging temperature. The magnetization and coercivity were enhanced as a result of aging above magnetic transition temperature. A maximum magnetization up to $54\mathrm{emu}∕\mathrm{g}$ and a magnetization difference between two phases of $28\mathrm{emu}∕\mathrm{g}$ was achieved in the alloy aged at $873\mathrm{K}$ . However, coercivity as large as $1.2\mathrm{kOe}$ was obtained in $573\mathrm{K}$ aged alloy, with a high saturation field, which can be understood in terms of domain wall pinning.

Ti-Ni-Cu shape memory thin films have attracted more attention as a result of the perfect combination of various advantages such as narrower thermal hysteresis, superior thermal cycling stability, higher strength and long-term functional fatigue. The prominent functional properties were closely related to their specific crystal structure and microstructural features. In the present paper, the microstructure in equiatomic, Ti-rich and (Ni,Cu)-rich shape memory thin films were reviewed. In addition, the corresponding results including martensitic transformation, microstructure and strain recovery characteristics of Ti-Ni-Cu thin films without precipitates and containing different types of precipitates were summarised. Besides, the mechanisms for obtaining the outstanding functional properties are discussed and reviewed, which can offer the theoretical basis to the design of Ti-Ni-Cu shape memory alloy thin film micro actuators with excellent performances.