Structural relaxation in amorphous materials under cyclic tension-compression loading

TL;DR

This study uses molecular dynamics simulations to explore how cyclic tension-compression loading causes structural relaxation in amorphous materials, leading to lower energy states and altered mechanical properties.

Contribution

It demonstrates that cyclic loading induces progressive energy relaxation and atomic rearrangements in amorphous solids, revealing mechanisms behind structural evolution under repeated stress.

Findings

Potential energy decreases with cycles, approaching a lower state.

Atomic rearrangements become collective and nonaffine over time.

Yield stress increases with higher cyclic strain amplitudes.

Abstract

The process of structural relaxation in disordered solids subjected to repeated tension-compression loading is studied using molecular dynamics simulations. The binary glass is prepared by rapid cooling well below the glass transition temperature and then periodically strained at constant volume. We find that the amorphous system is relocated to progressively lower potential energy states during hundreds of cycles, and the energy levels become deeper upon approaching critical strain amplitude from below. The decrease in potential energy is associated with collective nonaffine rearrangements of atoms, and their rescaled probability distribution becomes independent of the cycle number at sufficiently large time intervals. It is also shown that yielding during startup shear deformation occurs at larger values of the stress overshoot in samples that were cyclically loaded at higher strain amplitudes. These results might be useful for mechanical processing of amorphous alloys in order to reduce their energy and increase chemical resistivity and resistance to crystallization.