Low-fatigue and large room-temperature elastocaloric effect in a bulk Ti[formula omitted]Ni[formula omitted]Cu[formula omitted] alloy

Abstract

Large-scale applications of elastocaloric cooling demand bulk materials showing both large adiabatic temperature change (ΔTad) and low-fatigue characteristics at room temperature. Using cold-rolling and aging treatment, we synthesize a bulk Ti49.2Ni40.8Cu10 polycrystalline alloy that has microstructural features of nanocrystallinity and epitaxially related Ti(Ni,Cu)2 nanoprecipitates. It exhibits a large ΔTad of 13.8 K and a coefficient of performance of 13 at room temperature. Moreover, the degradation of ΔTad is only 0.3 K after 450 tensile cycles. We attribute the favorable properties to the enhanced reversibility of martensitic transformation during stress cycling, aided by the internal epitaxy-generated stress at the interface between the Ti(Ni,Cu)2 nanoprecipitates and matrix, together with grain refinement. The results indicate that the alloy offers a good balance of multiple objectives, holding promise for solid-state refrigeration applications.