A unique 'fishtail-like' four-way shape memory effect of compositionally graded NiTi

摘要

This paper reports a complex four-way shape memory effect of a compositionally graded NiTi thin plate. The composition gradient is created by surface diffusion of Ni into the plate. After a 15% tensile deformation pre-treatment, the compositionally graded plate exhibits a complex four-way shape memory effect in. bending mode, by which the metal exhibits a back-and-forth shape change upon a complete thermal cycle. This is analogous to a "fishtail-like" motion, resulting from the sequential transformation through the thickness of the plate as dictated by Ni content gradient. Such "four-way" shape memory effect has not been achieved in NiTi alloys before. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.