Large elastocaloric effect driven by stress-induced two-step structural transformation in a directionally solidified Ni55Mn18Ga27 alloy

Abstract

The first-order inter-martensitic transformation induced by temperature change or external stress is frequently observed in Ni-Mn-Ga alloys. Here, the inter-martensitic transformation is exploited to strengthen the elastocaloric effect. Through the stress-induced two-step structural transformation, i.e., martensitic and inter-martensitic transformation, giant adiabatic temperature change up to −10.7K is obtained in a directionally solidified Ni55Mn18Ga27 polycrystalline alloy with 〈001〉A preferred orientation, representing the highest value so far in Ni-Mn-Ga alloys. It is demonstrated that microstructure texturing together with introduction of inter-martensitic transformation could be an effective route to improve the elastocaloric properties in polycrystalline NiMn-based alloys.