Generalized stacking fault energy and dislocation properties in NiTi shape memory alloys

Abstract

Abstract Dislocations in the austenite phase of Nickel-Titanium (NiTi) shape memory alloys (SMAs) are of critical importance mainly due to their connection to the unrecoverable strains accumulated in SMAs during cyclic loadings, and also the key role of dislocations in the structure and energy of grain boundaries in these alloys. In this paper, we investigate the energy and structure of dislocations, and also the generalized stacking fault energies in NiTi austenite by implementing molecular dynamics (MD) simulations. Through our results the validity and accuracy of three different potentials, two EAM potentials with different cutoff radii and one 2NN MEAM potential, for studying defect related properties of NiTi alloys is investigated. It is shown that while none of these potentials are particularly trained for predicting defect properties in NiTi systems, they can be efficiently utilized to study the stacking fault energies, the energy and structure of edge dislocations, stress distributions at the vicinity of edge dislocations, and even the details of dislocation dissociation in NiTi austenite phase. Particularly our results can be used as a tool to select the appropriate potential for studying any problem related to a specific aspect of defects in austenite NiTi SMAs.