Elastic stress induced metastable local ordering in Cu-Zr-Al metallic glasses: A numerical simulation study

Abstract This work presents a study based on numerical simulations to describe the local structural evolution of Cu-Zr-Al amorphous alloys when moderate stresses are applied and removed. In particular, it will seek to recognize the formation of clusters with some degree of symmetry in the amorphous matrix and how these are altered depending on the mechanical stress experienced by them. The selected technique is classical molecular dynamics, using the ‘Embedded-atom method’ (EAM) and some other studies trying to identify local crystalline order (Common Neighbor Analysis, atomic centro-symmetry parameter, radial distribution functions and the reciprocal space pattern). The simulations confirm the local order/disorder mechanism based on the existence of ordered regions, which depends on the nature of the applied stress. Particularly, this work focused on performing simulations in time and stress regimes close to anelastic experimental conditions, which makes it different to other related computational reports that focus on regimes close to plastic deformation. The atomistic simulations provide strong evidence of the local ordering occurrence, in good concordance with early ultrasound assisted experiments on Cu-Zr-Al amorphous alloys, thus providing strong evidence of the local ordering occurrence in an elastic regime when uniaxial stress is applied. The reversibility of the system, when stress is removed, was also shown. The application of uniaxial stress favors the presence of different kind of local order structures, when compared with the situation of hydrostatic pressure.