Large elastocaloric effect in Mn and Ti co‐doped Co‐V‐Ga bulk polycrystalline alloys with low applied stress

Abstract Co‐V‐Ga‐based shape memory alloys have shown great potential in the field of solid‐state elastocaloric refrigeration due to their low stress hysteresis (∆ σ hys ) and excellent superelasticity. However, large applied stress and low adiabatic temperature change (Δ T ad ) greatly limit the application of Co‐V‐Ga‐based alloys as elastocaloric materials. Here, we have successfully achieved a breakthrough in material properties by innovatively introducing the co‐doping strategy of Mn and Ti elements. It was found that the synergistic effect of Mn and Ti significantly enhanced the mechanical properties of the Co 52 V 31 Ga 14 Mn 1 Ti 2 alloy through solid solution strengthening, fine grain strengthening, and precipitation strengthening mechanisms. A large Δ T ad of −11 K was obtained for the Co 52 V 31 Ga 14 Mn 1 Ti 2 bulk polycrystalline alloy under a very low applied stress of 380 MPa. This is mainly due to the strong texture of < 001 > A . Texture strengthening is the key factor to improve the elastocaloric effect of alloys. At the same time, the Co 52 V 31 Ga 14 Mn 1 Ti 2 alloy still maintains a Δ T ad of −4 K without an obvious attenuation trend after 350 elastocaloric cycles under the applied stress of 300 MPa. In addition, due to the low energy dissipation (∆ W ), the energy conversion efficiency of the elastocaloric response is greatly improved, so that the coefficient of performance (COP) of the Co 52 V 31 Ga 14 Mn 1 Ti 2 alloy material is as high as 28.9, far exceeding most of the current shape memory alloy elastocaloric materials. As a result, the co‐doping of Mn and Ti elements makes it possible to prepare an elastocaloric refrigeration alloy with low applied stress and a large elastocaloric effect.