Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression

Abstract

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu 68 Al 16 Zn 16 (CuAlZn) and Cu 73 Al 15 Mn 12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s −1 (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (Δ T ad ) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g −1 for the CuAlZn alloy and 5.0 J g −1 for the CuAlMn alloy. Potential coefficients of performance (COP mat ) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COP mat of approximately 13.3 for CuAlMn was obtained. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.