Reversible elastocaloric effect related to B2-R transformation in Ni50.5Ti49.5alloy

Abstract

In Ti-Ni alloys, the low hysteresis emanating from the B2 ↔ R transition enables a fine control of reversibility in elastocaloric effects when there are lower values of applied stress. In this paper, we reported a Ni50.5Ti49.5 alloy synthesized by arc melting promoting the R phase. Using energy dispersive x-ray analysis, differential scanning calorimetry, x-ray diffraction, and elongation measures as a function of temperature, we have studied properties in an isolated R phase. We observe that there are similarities between the isothermal entropy change curves and the reversible adiabatic temperature changes, where a maximum value of reversible isothermal entropy of 14.6 J kg-1 K-1 at 310 K is obtained when a stress of 222 MPa is applied. We show that precipitates formed on the R phase play a role in the elastic behavior affecting the values of adiabatic temperature change.