Linking high and low temperature plasticity in bulk metallic glasses: thermal activation, extreme value statistics and kinetic freezing

TL;DR

This paper presents a thermal activation model that links low-temperature plasticity in bulk metallic glasses to high-temperature behavior, incorporating extreme value statistics and kinetic freezing to explain the elastic-to-plastic transition.

Contribution

It introduces a unified theoretical framework connecting low and high temperature plasticity in bulk metallic glasses using potential energy landscape concepts.

Findings

The model reproduces the onset of macroscopic yield at low temperatures.

It explains the influence of extreme value statistics and kinetic freezing on deformation heterogeneity.

The theory smoothly transitions to high-temperature viscoplastic behavior near the glass transition.

Abstract

At temperatures well below their glass transition, the deformation properties of bulk metallic glasses are characterised by a sharp transition from elasticity to plasticity, a reproducible yield stress, and an approximately linear decrease of this stress with increasing temperature. In the present work it shown that when the well known properties of the under-cooled liquid regime, in terms of the underlying potential energy landscape, are assumed to be also valid at low temperature, a simple thermal activation model is able to reproduce the observed onset of macro-scopic yield. At these temperatures, the thermal accessibility of the complex potential energy landscape is drastically reduced, and the statistics of extreme value and the phenomenon of kinetic freezing become important, affecting the spatial heterogeneity of the irreversible structural transitions mediating the elastic-to-plastic transition. As the temperature increases and approaches the glass transition temperature, the theory is able to smoothly transit to the high temperature deformation regime where plasticity is known to be well described by thermally activated viscoplastic models.