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, we developed low‐temperature Ti49.2Ni50.8−xCox shape memory alloys 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 Ti49.2Ni44.8Co6 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 36MJ/m3 outperforms most shape memory alloys, showing a promise for low‐temperature actuator applications.This article is protected by copyright. All rights reserved.