Superelasticity and elastocaloric cooling capacity in stress-induced martensite aged [001]A-oriented Ni54Fe19Ga27 single crystals

The research paper presents a study of the effect of stress-induced martensite aging along the [001](A)-deformation axis of the sample on both elastocaloric cooling capacity and superelasticity in Ni54Fe19Ga27 single crystals in compression. It has been experimentally shown that L1(0)-martensite stabilization after the stress-induced martensite aging enhances the superelasticity parameters for the elastocaloric performance in the studied single crystals. In the stress-induced martensite aged Ni54Fe19Ga27 single crystals, the stress level of martensite formation sigma(Ms) and stress hysteresis delta sigma decrease by 130 MPa and by 16-17 MPa, respectively, compared with the as-grown crystals. Therefore, the stress-induced martensite aging increases the material efficiency for solid-state cooling systems: specific adiabatic temperature change per unit stress delta T-ad/sigma(Ms) increases by 4.4 times (delta T-ad/sigma(Ms) = 291.9 K/GPa (at T = 348 K)) and coefficient of performance reaches COP = 24.5 in stress-induced martensite aged crystals as compared with the as-grown crystals (delta T-ad/sigma(Ms )= 62.4 K/GPa (at T = 348 K), COP = 21.7). Smaller stress hysteresis corresponds to less energy dissipation in an operating cycle, which is also certainly useful for optimizing elastocaloric properties of a material. Moreover, both as-grown and stress-induced martensite aged crystals demonstrate high cyclic stability during loading/unloading cycles and weak temperature dependence of the elastocaloric cooling capacity delta T-ad = 10.3-11.0 K in a wide operating temperature range up to 145-197 K. Thus, stress-induced martensite aged Ni(54)Fe(19)Ga(27 )single crystals oriented along the [001](A)- direction are expected to be promising materials for elastocaloric application.

Automated summary

The research paper discusses the impact of stress-induced martensite aging on the elastocaloric cooling capacity and superelasticity of Ni54Fe19Ga27 single crystals. The study shows that martensite aging enhances the superelasticity parameters and improves the performance of elastocaloric cooling systems. Additionally, martensite aging reduces stress hysteresis and energy dissipation, and exhibits high cyclic stability in a wide temperature range.