Promising elastocaloric properties of sintered polycrystalline NiMnGa produced by open die pressing

Abstract

AbstractThe increasing interest in the development of multicaloric materials for solid-state cooling applications is giving rise to the investigation of elastocaloric performance of ferromagnetic Shape Memory Alloys (FeSMA). Moreover, some sintering processes have been proposed to overcome the well-known brittleness of these alloys. In this context, a novel application of the open die pressing (ODP) method for the preparation of NiMnGa polycrystalline samples sets the chance to have interesting mechanical properties, until now never reported in literature. In this work, a tunable optimization of microstructure is presented and the elastocaloric properties are investigated by different mechanical approaches and direct measurement of adiabatic ΔT values. It is observed, for the first time, a polycrystalline NiMnGa alloy that exhibits an extremely stable mechanical and thermal response upon 200 adiabatic compression cycles. The best performance consisted in a ΔS peak of 35 J/(kg °C) and an adiabatic ΔT value of ± 4 °C in the first 10 cycles and + 3,75 / − 4 °C in stabilized conditions over 200 cycles.