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

Complex “4-way” shape memory behaviour of a compositionally graded NiTi thin strip after 15% of tensile deformation. In this figure, the sample bends towards one direction (increase of curvature) initially and then bends backwards (decrease of curvature) upon one cooling (the blue curve). The same process repeats also during heating, thus exhibiting shape change in four directions within one complete thermal cycle.