Stable elastocaloric effect in a directionally solidified Ni54Fe19Ga27 alloy under low driving stress

Abstract

Heusler-type Ni–Fe–Ga-based alloys exhibit a large elastocaloric effect under low driving stress, yet the intrinsic brittleness of polycrystalline alloys significantly cripples their cyclic stability during mechanical cycles. In this study, we present the enhanced cyclability of the elastocaloric response in a 〈001〉A oriented Ni54Fe19Ga27 alloy, due to the incorporation of a low content of the ductile γ-phase through solution treatment at 1373 K. This microstructure manipulation not only substantially improves the mechanical properties but also yields a very low critical stress of ∼38 MPa for inducing the martensitic transformation. Moreover, the present alloy shows a stable long-term elastocaloric response under a low stress of ∼70 MPa, with a reversible adiabatic temperature change of ∼6 K sustained for more than 1.5 × 105 cycles. Developing high-performance elastocaloric materials with long fatigue life and low driving stress is of great significance for solid-state elastocaloric cooling.