Cryogenic superelasticity and elastocaloric effect in a nanostructured Ti-Ni-Co alloy

We report a nanostructured Ti_49.2Ni_44.8Co₆ (at.%) alloy that exhibits a fully recoverable tensile superelasticity (∼ 6%) with high critical stress (> 500 MPa) spanning low temperatures from -150 to -50 ^∘C. An adiabatic temperature change reaches 10.7 K during fast unloading at -50 ^∘C. The low-temperature tensile superelastic stress and adiabatic temperature change outperform most shape memory alloys. Moreover, both properties exhibit negligible degradation during dozens of stress cycles. We attribute these favorable functionalities to the enhanced thermodynamic stability of parent phase and the remarkable strengthening effect on the matrix by partially recrystallized nanocrystalline structure with dispersed Ti₃Ni₄ nanoprecipitates.