Research progress on superelastic materials

Superelastic (SE) materials, characterized by unique nonlinear stress-strain relationships and large deformation recoverability, provide a critical material foundation for lightweight structures, flexible mechanisms, and smart devices operating under large deformation conditions. These materials can be broadly classified into four categories: shape memory alloys (SMA), shape memory polymers (SMP), shape memory polymer composites (SMPC), and conductive polymer composites (CPC). Among them, NiTi SMAs-representing a typical SMA system-are widely employed in biomedical and damping applications; however, their high cost and the potential release of Ni ions during long-term implantation or in complex service environments have spurred the development of Cu-based, Fe-based, and Ni-free Ti-based SMA systems. Furthermore, ferromagnetic shape memory alloys such as Ni-Mn-Ga exemplify the extension of SMAs toward magnetic responsiveness and multi-field coupling. SMPs and SMPCs exhibit multi-stimuli responsiveness, and when integrated with 4D printing technology, they offer lightweight solutions for deployable structures. CPCs, by incorporating conductive phases into an elastic polymer matrix, achieve stable strain-electric signal coupling while retaining high elongation and low modulus, thereby providing novel approaches for flexible electronics and wearable devices. This paper presents a systematic review of recent advances in SE materials, first outlining their classification and fundamental properties, then elaborating on the preparation methods and representative application scenarios of each material type, and finally discussing future research directions to support the continued development of SE materials.