Relaxation dynamics in amorphous alloys under asymmetric cyclic shear deformation

TL;DR

This study uses molecular dynamics simulations to explore how asymmetric cyclic shear influences structural relaxation and yielding in amorphous alloys, revealing how glass stability and cyclic loading affect material properties and transition behaviors.

Contribution

It demonstrates the impact of asymmetric cyclic shear on relaxation and yielding in amorphous alloys, highlighting the role of glass stability and cyclic strain amplitude.

Findings

Rapidly cooled glasses relax to lower energy states under cyclic shear.

Power-law distribution of displacements near critical strain amplitude.

Yielding can be delayed for hundreds of cycles near a critical strain.

Abstract

The influence of cyclic loading and glass stability on structural relaxation and yielding transition in amorphous alloys was investigated using molecular dynamics simulations. We considered a binary mixture cooled deep into the glass phase and subjected to cyclic shear deformation where strain varies periodically but remains positive. We found that rapidly cooled glasses under asymmetric cyclic shear gradually evolve towards states with lower potential energy and finite stress at zero strain. At the strain amplitude just below a critical value, the rescaled distributions of nonaffine displacements converge to a power-law decay with an exponent of about -2 upon increasing number of cycles. By contrast, more stable glasses yield at lower strain amplitudes, and the yielding transition can be delayed for hundreds of cycles when the strain amplitude is near a critical value. These results can be useful for the design of novel thermo-mechanical processing methods to improve mechanical and physical properties of metallic glasses.