Small stress-hysteresis in a nanocrystalline TiNiCuFe alloy for elastocaloric applications over wide temperature window

Shape memory alloys (SMAs) with small stress-hysteresis and wide superelasticity temperature window are highly desired for elastocaloric applications. In this study, a nanocrystalline Ti₅₀Ni₄₂Cu₆Fe₂ SMA is fabricated by casting, forging, wire-drawing and annealing. The alloy exhibits superelasticity with a narrow average stress-hysteresis of ∼180 MPa over a temperature window from 213 K to 323 K. The temperature change of the elastocaloric effect is calculated to be ∼28 K. In situ synchrotron X-ray diffraction measurements suggest that the small hysteresis is probably attributed to the enhanced lattice compatibility as quantified by the cofactor condition parameters (λ₂, X_I and X_II).