Enhanced cyclic stability of elastocaloric effect in oligocrystalline Cu–Al–Mn microwires via cold-drawing

Abstract

The cyclic stability of the elastocaloric effect (eCE) is an important performance for elastocaloric refrigeration. Our previously work showed that Cu-Al-Mn microwires with bamboo grains exhibited favorable eCE with small hysteresis. Here, we demonstrated that oligocrystalline grain architecture in Cu-Al-Mn microwires created via multi-step cold-drawing having favorable eCE cyclic stability. The oligocrystalline grains exhibited a preferential 〈101〉 orientation along the wire axis. The annealed microwire with diameter 130 µm showed stress-induced entropy change (ΔSσ) of 5.0 J kg−1 K−1 but degraded rapidly after ~ 15 cycles. On the other hand, the as-drawn microwire with diameter 130 µm showed a large entropy change (ΔSσ) of 10.3 J kg−1 K−1 and a temperature change (ΔT) of 4.5 K with fast fatigue rate. Moreover, the microwire exhibited a smaller ΔT = 3.0 K with stability up to 275 cycles for further cold-drawn to diameter 80 µm. The enhanced cyclic stability of elastocaloric effect in as-drawn microwire was attributed the favorable grain orientation and enhanced yield strength induced by cold-drawing. This work is instructive for designing high-performance Cu-based elastocaloric materials for solid-state cooling applications.