Atomistic simulations of AuTi high-temperature shape memory alloys

Abstract

Herein, the atomic-scale phase transformation and deformation processes of AuTi shape memory alloys for high-temperature applications were investigated using molecular dynamics simulations based on a newly developed interatomic potential for the Au-Ti binary system. The developed second nearest-neighbor modified embedded-atom method potential exhibited good accuracy and transferability to reproduce various physical properties of the target alloy system, particularly in properties related to the reversible phase transformation of AuTi high-temperature shape memory alloys. As a conceivable application of the interatomic potential, the temperature-induced phase transformation of AuTi single-crystal shape memory alloys and the effect of off-stoichiometry on the phase transformation behavior were examined. Molecular dynamics simulations revealed that the transformation temperature and thermal hysteresis decreased with increasing Ti content, consistent with the reported experimental trend, suggesting that the reduced volume difference between the austenite and martensite phases was closely related to the reduced thermal hysteresis. We further examined the mechanical response and resultant superelasticity of nanocrystalline AuTi alloys to demonstrate that the cyclic deformation of nanocrystalline alloys exhibited a transformation ratcheting behavior caused by the plastic deformation of amorphous-like grain boundary region.