Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression

This paper reports the elastocaloric effect of two Cubased shape memory alloys: Cu₆₈ Al₁₆ Zn,₁₆ (CuAlZn) and Cu₇₃ Al₁₅ Mn₁₂ (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 (ΔT_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 (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat 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'.