Large elastocaloric effect with high refrigeration efficiency in a polycrystalline Co ₅₀ V ₃₅ Ga ₁₅ Heusler alloy

Abstract Superelastic martensitic transformation (MT) confers a considerable elastocaloric response to shape memory alloys, but the significant hysteretic loss cripples the energy conversion efficiency. In the present work, large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co 50 V 35 Ga 15 Heusler alloy. Experimental results show that the studied alloy undergoes a paramagnetic type MT from L 2 1 cubic austenite to D 0 22 tetragonal martensite with a small thermal hysteresis of ~ 3 K. By carefully examining the strain rate dependence of superelastic response, it is also found that the stress hysteresis consists of two components including intrinsic stress hysteresis caused by inherent attribute of MT and extrinsic stress hysteresis aroused by applied strain rate. Accordingly, we put forward a strain relaxation equation to separate the relative contributions between and quantitatively, which demonstrates that a small is conducive to substantial decrease in . Moreover, associated with stress‐induced superelastic MT, large reversible adiabatic temperature changes higher than 11 K are achieved under an applied strain of 6.5% over a temperature range of at least 60 K. With the combination of a large elastocaloric cooling capacity and a low energy dissipation, significant improvements in refrigeration efficiency can be obtained in a wide strain range, being superior to those reported in most of typical elastocaloric materials near room temperature.