Enhanced working stability of elastocaloric effects in polycrystalline Ni-Fe-Ga dual phase alloy

Stable elastocaloric effect (eCE) over multiple stress cycles is an indispensable aspect for the commercialization of elastocaloric refrigeration. Here, we addressed the enhanced functional stability in polycrystalline Ni53.2 +/- 0.4Fe19.4 +/- 0.2Ga27.4 +/- 0.6 dual-phase alloy, where interstitial gamma-phase was incorporated via aging precipitation. The intergranular gamma-precipitates confirmed the reversible superelastic effects at room temperature (296 K), which is greatly conducive to multiple interphase movement. As a consequence, notable adiabatic temperature change (dTad) 6.2 K with a large coefficient of performance (COPmat) 14.5 was achieved under maximum stress 300 MPa. A stable eCE cooling performance (dTad similar to 2.6 K) over 500 superelastic cycles with insignificant degradation was found under nominal stress 250 MPa. Consequently, the current work demonstrates that manipulating the microstructure by incorporating the interstitial secondary phase is a promising approach to enhance the mechanical and functional properties of ferromagnetic shape memory alloys (FMSMAs) for solidstate cooling technology.