Mechanical behavior of Ni[formula omitted]Ti[formula omitted] shape memory alloys with void defects

Abstract

Superelasticity of NixTi100−x B2 shape memory alloys (SMAs) with different atomic compositions and void defects are investigated using molecular dynamics simulations. In the first part of this study, the effect of species content on the martensitic transformation is explored, with x ranging from 48% to 52%. All samples displayed similar behavior under compression, where transformation from B2 to B19’ was observed. On the other hand, under tension, both Ni48Ti52 and Ni50Ti50 displayed single-step transformation from B2 to L10, while the Ni-rich sample exhibited a simultaneous double-step transformation from B2 to B19’ to L10. The mechanical performance of the samples with voids under compression was also explored. The void surface was found to act as a barrier, hindering the phase transformation to B19’ structure and its elastic response, ultimately reducing the maximum stress prior to fracture. Statistical methods established connections between various properties and offered mathematical models to correlate the initial setup variables Ni content and void radius, with properties derived from deformation tests. Consequently, this study provides both an atomic description of the deformation behavior of NiTi SMAs and a statistical framework for establishing the relationships between materials properties.