Improved cyclic stability of elastocaloric effect in NiTi alloys via low-angle cyclic torsion

NiTi shape memory alloys, as one of the most developed and commercially produced shape memory alloys, are among the most promising candidates for elastocaloric effects refrigeration. However, attaining long-term cyclic stability remains a key challenge for practical applications. Contemporary research predominantly emphasizes adiabatic temperature change, with limited strategies addressing fatigue life. We present a novel low-angle cyclic torsion process that enhances the cyclic stability of elastocaloric effects by an order of magnitude, extending the cycle life of commercial coarse-grained NiTi shape memory alloys from 285 to 1114 cycles while maintaining a stable adiabatic temperature change of ∼-8 K. This enhancement is attributed to a gradient structure that considerably inhibits the production of dislocations during the subsequent cyclic phase transformation. This strategy offers a promising pathway to improve the cyclic stability of elastocaloric effects.