Enhancing the elastocaloric effect in Ni–Mn–Ga alloys through the coupling of magnetic transition and two-step structural transformation

Abstract

Elastocaloric effect driven by uniaxial stress in the Ni–Mn–Ga alloys can be greatly enhanced through introducing magnetic transition or inter-martensitic transformation to martensitic transformation. Here, we present large elastocaloric effect in a ⟨0 0 1⟩A textured Ni55Mn19Ga25Ti1 polycrystalline alloy prepared by directional solidification by exploiting the coupled multiple phase transformations, i.e., paramagnetic-ferromagnetic transition, martensitic transformation, and inter-martensitic transformation. Owing to such magneto-multistructural transformation, the transformation entropy change related to the inverse transformation is enhanced to 29.6 J kg−1 K−1. Consequently, on unloading from a compressive stress of 180 MPa, a large adiabatic temperature change of −12.9 K and specific adiabatic temperature change of −72 K GPa−1 are achieved, being much superior over those in the Ni–Mn–Ga based alloys obtained previously.