Structural relaxation affecting shear transformation avalanches in metallic glasses

TL;DR

This study uses molecular dynamics simulations to explore how structural relaxation influences shear transformation avalanches in metallic glasses, revealing differences in avalanche size, shape, and localization between less-relaxed and well-relaxed states.

Contribution

It provides new insights into the impact of structural relaxation on avalanche behavior and shear localization in metallic glasses through detailed simulation analysis.

Findings

Power-law statistics of avalanches are consistent across models with different relaxation levels.

Well-relaxed glasses exhibit shear localization and anisotropic avalanche regions.

A correlation exists between avalanche size and anisotropy in well-relaxed glasses.

Abstract

Avalanche behaviors, characterized by power-law statistics and structural relaxation that induces shear localization in amorphous plasticity, play an essential role in deciding the mechanical properties of amorphous metallic solids (i.e., metallic glasses). However, their interdependence is still not fully understood. To investigate the influence of structural relaxation on elementary avalanche behavior, we perform molecular-dynamics simulations for the shear deformation test of metallic glasses using two typical metallic-glass models comprising a less-relaxed (as-quenched) glass and a well-relaxed (well-aged) glass exhibiting a relatively homogeneous deformation and a shear-band-like heterogeneous deformation, respectively. The data on elementary avalanches obtained from both glass models follow the same power-law statistics with different maximum event sizes, and the well-relaxed glass shows shear localization. Evaluating the spatial correlation functions of the nonaffine squared displacements of atoms during each elementary avalanche event, we observe that the shapes of the elementary avalanche regions in the well-relaxed glasses tend to be anisotropic, whereas those in the less-relaxed glasses are relatively isotropic. Furthermore, we demonstrate that a temporal clustering in the direction of the avalanche propagation emerges, and a considerable correlation between the anisotropy and avalanche size exists in the well-relaxed glass model.