Elastocaloric effect in Ni50Fe19Ga27Co4 single crystals

Abstract

The elastocaloric effect of the [001]P and [111]P orientated (subscript P represents the parent phase) Ni50Fe19Ga27Co4 (at.%) single crystals exhibiting first-order martensitic transformations have been studied at temperatures of 298–448K under different compressive stresses. The adiabatic temperature change ΔTadi shows a significant dependence on the crystal orientation. The temperature decrease caused by adiabatic removal of stress 300MPa reaches to about 9–10K in a temperature range 328–398K for [001]P specimen and 3K at temperature near Af for [111]P one. The large elastocaloric effect is essentially attributed to the entropy change during the stress-induced martensitic transformation. The accumulated defect such as the a/2〈112〉 L10 type dislocation is the main reason for the attenuation of the elastocaloric effect in a fatigue test up to 3000 cycles. Large specific adiabatic temperature (|ΔTadi/Δσ|≈35K/GPa), wide specific effective temperature window (|ΔTwin/Δσ|≈320K/GPa) and high coefficient of performance (COP≈14) in a temperature range as wide as 50K during the unloading process enable the [001]P orientated Ni50Fe19Ga27Co4 single crystal as a potential elastocaloric material.