Effect of annealed disorder on the plasticity of amorphous solids

TL;DR

This study explores how annealed disorder, introduced via heavy impurities, influences the plasticity and failure mechanisms of amorphous solids, revealing a suppression of shear band formation and a transition to localized plastic events.

Contribution

It demonstrates that increasing impurity mass enhances shear modulus and yield stress, and induces a transition from distributed to localized plasticity in amorphous solids.

Findings

Shear modulus and yield stress increase with impurity mass.

Plastic events become localized above a critical impurity mass.

Transition from power-law to exponential decay in spatial correlations.

Abstract

We investigate the effect of annealed disorder on the mechanical properties and plasticity of a modeled amorphous solid by introducing a small fraction of heavy impurities into the material which resembles real experimental systems. The disorder being mobile, the total degrees of freedom and the potential energy landscape of the pure system are preserved in our model. The mechanical failure and the shear band formation in the amorphous solid in the presence of annealed disorder are studied at the microscopic level by employing the finite shear deformation protocol at nonzero temperature. A significant enhancement in the shear modulus and yield stress is observed as a function of the heaviness of the impurity particles. Via the analysis of the non-affine displacement field and the microscopic strain fluctuations and the nature of their spatial correlations we find that the shear band formation in the plastic regime is gradually suppressed with increasing impurity mass. Eventually, a critical mass of the disordered particles is identified above which the plastic events become completely localized. This is marked by a transition from a power law to an exponential decay in the spatial correlations non-affine displacement field. Likewise, a similar change is observed in the strain correlation function, transitioning from a slower $1/r$ decay to a more rapid $1/r^3$ decay. Finally, the effect shear rate on the plastic events in the presence of annealed disorder is explored.