Tuning brittleness in multi-component metallic glasses through chemical disorder aging

TL;DR

This study uses molecular dynamics simulations to show that chemical aging in multi-component metallic glasses sharpens the elastic-plastic transition by increasing local order and shear zone localization.

Contribution

It introduces a hybrid Monte-Carlo-MD method to investigate how glass aging affects shear localization and the elastic-plastic transition in metallic glasses.

Findings

Aging sharpens the elastic-plastic transition.

Localized shear patterns develop with aging.

Susceptibility to plastic rearrangements correlates with local order.

Abstract

Shear localization in slowly-driven bulk metallic glasses (BMGs) is typically accompanied by a sharp drop in the bulk stress response as a signature of the plastic yielding transition. It is also observed that the sharpness of this elastic-plastic dynamical transition depends on the extent of local chemical and microstructural orders, as well as the glass preparation protocol ( ie. thermal annealing). Here, we investigate sheared multi-element BMGs in molecular dynamics (MD) simulations, and demonstrate that glass aging, implemented through a hybrid Monte-Carlo(MC)-MD process, sharpens the elastic-plastic transition through a distinct crossover, seen in strain patterns that gradually shift from diffuse features in as-quenched samples to localized (yet system-spanning) patterns in well-annealed glasses. This effect of glass aging on the elastic-plastic transition is found to be correlated to the inherent interplay between aging-induced icosahedra ordering and co-operative formation of shear transformation zones. The observed crossover is quantified through a measure of the age-dependent susceptibility to plastic rearrangements, exhibiting strong (anti-)correlations to local ordering features, and the corresponding spatial correlation length grows with the aging timescale.