Accessing a broader range of energy states in metallic glasses by variable-amplitude oscillatory shear

TL;DR

This study uses molecular dynamics simulations to explore how variable-amplitude oscillatory shear influences the energy states and mechanical properties of metallic glasses, revealing methods to rejuvenate or relax the material depending on initial conditions.

Contribution

It demonstrates how alternating shear amplitudes can either rejuvenate well-annealed glasses or relax poorly annealed ones, advancing understanding of energy landscape exploration in amorphous materials.

Findings

Small-amplitude loading can rejuvenate well-annealed glasses.

Alternating large and small amplitudes can lower energy states in poorly annealed glasses.

Plastic rearrangements are smaller than system size, maintaining structural integrity.

Abstract

The influence of variable-amplitude loading on the potential energy and mechanical properties of amorphous materials is investigated using molecular dynamics simulations. We study a binary mixture that is either rapidly or slowly cooled across the glass transition temperature and then subjected to a sequence of shear cycles with strain amplitudes above and below the yielding strain. It was found that well annealed glasses can be rejuvenated by small-amplitude loading if the strain amplitude is occasionally increased above the critical value. By contrast, poorly annealed glasses are relocated to progressively lower energy states when subyield cycles are alternated with large-amplitude cycles that facilitate exploration of the potential energy landscape. The analysis of nonaffine displacements revealed that in both cases, the typical size of plastic rearrangements varies depending on the strain amplitude and number of cycles, but remains smaller than the system size, thus preserving structural integrity of amorphous samples.