On the origin of Lüders-like deformation of NiTi shape memory alloys

Polycrystalline NiTi shape memory alloys deformed in tension tend to exhibit localization and propagation of deformation in macroscopic shear bands. The propagation of the deformation bands is characterized by a plateau-type stress-strain curve. Such behavior has been reported only for NiTi alloys and only in tension. The reason for this behavior is still unclear although different hypotheses have been proposed in the literature. This article briefly summarizes relevant experimental evidences and offers an explanation based on micromechanics modelling of pseudoelasticity of polycrystalline NiTi.