Effect of homogenization treatment on elastocaloric effect in a Ti25Zr10Hf15Ni24Cu26 high entropy shape memory alloy

Integrating the concept of high entropy alloys into the design of shape memory alloys provides a novel strategy to tune the mechanical and functional properties. In this work, a Ti 25 Zr 10 Hf 15 Ni 24 Cu 26 high entropy shape memory alloy was developed, and the influence of homogenization treatment temperatures (i.e., 973 K, 1,073 K, and 1,173 K for 48 h) and holding time (i.e., 6 h, 12 h, 24 h, 48 h, and 96 h at 1,173 K) on the martensitic transformation and elastocaloric effect was investigated. It is shown that increasing the homogenization treatment temperature or holding time results in the enhanced martensitic transformation temperatures as well as the transformation entropy changes. Consequently, the elastocaloric response is substantially promoted by homogenization treatment. In particular, the homogenization treatment at 1,173 K for 48 h yields more remarkable elastocaloric response and the stress-induced temperature change can be as large as 12.3 K. Such enhanced elastocaloric performance is attributed to the improved degree of composition homogeneity and the elimination of dendritic microstructure, thereby giving rise to enhanced transformation entropy change and reduced internal constraints on stress-induced transformation. Therefore, proper homogenization treatment can be employed to manipulate the elastocaloric performance of high entropy shape memory alloys.