Low-Fatigue and Large Room-Temperature Elastocaloric Effect in a Bulk Ti 49.2 Ni 40.8 Cu 10 Alloy

Large-scale applications of elastocaloric cooling demand bulk materials showing both large adiabatic temperature change (∆Tad) and low-fatigue characteristics at room temperature. Here we synthesize a bulk Ti49.2Ni40.8Cu10 polycrystalline alloy microstructurally featured by nanocrystalinity and epitaxially related Ti(Ni,Cu) 2 nanoprecipitates through cold-rolling and aging treatment. It exhibits a large ∆Tad of 13.8 K and a high coefficient of performance value of 13 at room temperature. Moreover, the degradation of ∆Tad is only 0.3 K after 450 tensile cycles. The results indicate that the alloy offers a good balance of multiple objectives, holding promise for solid-state refrigeration applications. 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.