Tailorable stress window of stress-induced martensitic transition in NiTi/W nanostructured multilayer films

Abstract NiTi thin films showed superplasticity with recovery strain up to 8%, however their strongly non-linear elasticity caused imprecise position control in MEMS requiring immediate and progressive control. Here, we report NiTi/W nanostructured multilayer films with tailorable stress window via layer spacing modulation. The stress window could be enlarged up to three times larger than that of single-layered NiTi film. Coherent phase boundary between B2 and α-W as well as the large transition strain of NiTi layer led to multilayers collaborative deformation without dislocation slip, making NiTi/W films large strain and strength. On the other hand, grain growth of NiTi layers was confined by W layers, thus layer spacing change could successfully modify the martensitic transition start stress of B2–B19’.