Non-equilibrium first order transition marks the mechanical failure of glasses

TL;DR

This paper demonstrates that the mechanical failure of glasses under stress occurs via a sharp, first order-like transition, characterized by a symmetry change from solid to liquid structure, offering new insights into glass yielding.

Contribution

The study provides experimental evidence of a first order-like transition during stress-induced flow in glasses, revealing a symmetry change from anisotropic to isotropic structure.

Findings

Identification of a sharp symmetry change at yielding

Observation of liquid-like intensity fluctuations

Evidence of a first order-like transition during flow onset

Abstract

Glasses acquire their solid-like properties by cooling from the supercooled liquid via a continuous transition known as the glass transition. Recent research on soft glasses indicates that besides temperature, another route to liquify glasses is by application of stress that forces relaxation and flow. Here we provide experimental evidence that the stress-induced onset of flow of glasses occurs via a sharp first order-like transition. Using simultaneous x-ray scattering during the oscillatory rheology of a colloidal glass, we identify a sharp symmetry change from anisotropic solid to isotropic liquid structure at the transition from the linear to the nonlinear regime. Concomitantly, intensity fluctuations sharply acquire liquid distributions. These observations identify the yielding of glasses to increasing stress as sharp affine-to-nonaffine transition, providing a new conceptual paradigm of the yielding of this technologically important class of materials, and offering new perspectives on the glass transition.