Compositionally graded NiTi plate prepared by diffusion annealing

This paper reports the creation of functionally graded NiTi thin plates with varying composition through thickness. The composition gradient is created by surface diffusing Ni into thin equiatomic NiTi plates. The compositional gradient results in a gradient of the critical temperatures for martensitic transformation in the alloy. The functionally graded NiTi plates exhibit unique reversible one-way shape recovery behavior in a “fishtail-like” motion. Such mechanical behavior offers new options for innovative designs of NiTi, in particular actuators and bionics devices.