Nanostructured Ti–Ni–Co Alloys Showing Shape‐Memory Actuation of Large Work Output at Low Temperature

Abstract

In the present study, by combining the effect of point defect doping and nanostructure, low‐temperature shape‐memory alloys (SMAs) are developed showing good actuation property. The doping of Co into Ti–Ni host alloy suppresses the martensitic transformation to lower temperature. By post‐deformation annealing, the partially recrystallized state containing dense dislocations and nanoprecipitates is achieved. And, this remarkably strengthens the matrix to avoid irreversible strain under large external load. A alloy thereby exhibits a recoverable actuation strain of 4.5% under biased tensile stress of 800 MPa at temperatures below −50 °C. The work output up to outperforms most SMAs, showing a promise for low‐temperature actuator applications.