Development of Copper-Based Elastocaloric Materials

The elastocaloric effect has drawn attention as a promising approach for solid-state heating or cooling, offering an alternative to traditional refrigeration technologies by leveraging the stress-induced martensitic transformation of shape memory alloys (SMAs). Conventional cooling systems rely on liquid refrigerants, including hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), which pose significant environmental and safety hazards, thereby requiring continuous leak detection. The current state-of-the-art elastocaloric materials are NiTi-based alloys. Although nitinol exhibits exceptional thermo-mechanical performance, it is expensive to manufacture and requires a high stress >600 MPa to induce a phase transformation. Industrial adoption of elastocaloric cooling requires a more cost-effective material. Copper-based SMAs have attracted interest, demonstrating competitive properties while being accessible at a low cost and with less energy-intensive fabrication methods. Ternary alloys such as CuAlZn and CuAlNi have been widely characterized; however, both are inherently brittle and suffer from poor functional stability. The CuAlMn system offers increased ductility and mechanical performance achieved through composition tuning and alloying elements. Nonetheless, the material has limitations, including low enthalpy, high austenite-finish (A_f) transformation temperature, and low fatigue life. Therefore, tailoring the performance through quaternary alloying elements and thermomechanical processing is essential for developing CuAlMn-based elastocaloric materials.