Solid-state refrigeration of shape memory alloy-based elastocaloric materials: A review focusing on preparation methods, properties and development

Sustainable development represents a vital global strategic goal. In the field of microcooling, green and environmentally friendly solid-state refrigeration technologies show great potential to replace vapor compression refrigeration technologies based on hydrofluorocarbon refrigerants. Shape memory alloys (SMAs) have received increasing interest in recent years as promising elastocaloric materials (eCMs) that induce martensitic phase transformations, which exhibit heat release and absorption upon the application and removal of stress fields. This work reviews the main preparation methods and recent advances in solid-state refrigerants based on SMAs, such as the more studied methods of melting and casting, rolling, and drawing, and the less studied methods of sputtering deposition, and additive manufacturing. The main properties of the eCM-based solid-state refrigerants were analyzed, including the elastocaloric effect (eCE), operating temperature window, stress hysteresis, and cycle stability. Challenges in the commercialization of solid-state refrigeration technology, including SMA-based eCM and their key properties, are discussed. The characteristics and applicability of the different preparation methods are compared, and the advantages and limitations of the methods are summarized. Furthermore, the authors discus the latest research achievements and development directions of SMA-based eCMs to inspire the exploration of new technologies for eCM with excellent eCE and fatigue properties, as these properties are the keys to solid-state cooling technology. Therefore, this comprehensive review is expected to be useful for research on developing eCMs with excellent performance for commercial application in solid-state refrigeration technology.