Ultrahigh cyclic stability and large elastocaloric effect in Ge doped Co-V-Ga shape memory alloys

Abstract

Following significant developments in solid-state cooling, elastothermic refrigeration has received wide attention, while further requiring better elastocaloric effect and more excellent mechanical cycle performance. In this study, we report that by doping Ge into Co-V-Ga-based Heusler alloys and controlling Ge content, the martensitic transformation temperature was adjusted to near room temperature, while reducing the critical stress required for martensitic transformation. The Co₅₀V₃₅Ga₁₄Ge₁ alloy exhibits a large adiabatic temperature change of 10.4 K at 500 MPa while possessing a compressive strength of 1,989 MPa. It also offers exceptional superelasticity with a fully recoverable strain of 4.8%, a low driving force of 167.5 MPa and narrow stress hysteresis of 43 MPa. At the same time, the temperature change is stabilized at 8.8 K after 10,000 cycles under 500 MPa in a cycling test, showing almost no degradation.