Nanocomposite NiTi shape memory alloy with high strength and fatigue resistance

Many established, but also potential future applications of NiTi-based shape memory alloys (SMA) in biomedical devices and solid-state refrigeration require long fatigue life with 107–109 duty cycles1,2. However, improving the resistance NiTi often compromises other mechanical functional properties3,4. Existing efforts to improve SMA include composition control for coherent phase boundaries5–7 microstructure such as precipitation8,9 grain-size reduction3,4. Here, we extend strategy nanoscale via a hybrid heterogenous nanostructure. We produced superelastic nanocomposite crystalline amorphous phases severe plastic deformation low-temperature annealing. The as-produced possesses recoverable strain 4.3% yield strength 2.3 GPa. In cyclic compression experiments, nanostructured micropillars endure over 108 reversible-phase-transition cycles under stress 1.8 GPa. attribute enhanced properties mutual strengthening nanosized where suppresses dislocation slip while hinders shear band propagation phase. synergy at could be an effective method SMA. Increasing behaviour. Introducing mixed nanostructure can enable superelasticity 4.3%, 2.3 GPa reversible-phase transition