<title>Anisotropy of detwinning process in textured NiTi shape memory alloy</title>

Abstract

Detwinning of thermally formed martensite twins in shape memory alloys leads to a macroscopic stress-plateau in the stress-strain curves. The response of twinned domains under stresses plays a critical role in the anisotropy of both the mechanical and the thermomechanical behavior of especially textured shape memory alloys. A recent result has shown that the relation between the shear direction of certainly distributed martensite twins and the loading direction is the key to understand both the microscopic and the macroscopic deformation processes. Based on this result, the present research has systematically analyzed the orientation-dependence of the detwinning process from a crystallographic approach and using mechanics of heterogeneous materials. The results are found to be well coherent with the experimental observations without superstitiously imposed conditions. For a NiTi sheet with given textures, the predicted response of two types of martensite twins, namely, type II and compound twins as a function of loading direction, agrees well with the experimental observations.