Ultrahigh Poisson's ratio glasses

TL;DR

This study uses computer simulations to create metallic glasses with ultrahigh Poisson's ratios, exceeding laboratory limits, and explores how their microscopic properties relate to their elasticity and failure modes.

Contribution

The paper introduces a simple model that produces ultrahigh Poisson's ratio metallic glasses and investigates the micromechanical origins of their high incompressibility.

Findings

Achieved Poisson's ratio up to 0.45, surpassing laboratory metallic glasses.

Linked high Poisson's ratio to softer glassy excitations and unjamming transition.

Established correlations between microscopic excitations, elasticity, and disorder.

Abstract

The manner in which metallic glasses fail under external loading is known to correlate well with those glasses' Poisson's ratio $\nu$: low-$\nu$ (compressible) glasses typically feature brittle failure patterns with scarce plastic deformation, while high-$\nu$ (incompressible) glasses typically fail in a ductile manner, accompanied by a high degree of plastic deformation and extensive liquid-like flow. Since the technological utility of metallic glasses depends on their ductility, materials scientists have been concerned with fabricating high-$\nu$ glassy alloys. To shed light on the underlying micromechanical origin of high-$\nu$ metallic glasses, we employ computer simulations of a simple glass-forming model with a single tunable parameter that controls the interparticle-potential's stiffness. We show that the presented model gives rise to ultra high-$\nu$ glasses, reaching $\nu\!=\!0.45$ and thus exceeding the most incompressible laboratory metallic glass. We discuss the possible role of the so-called unjamming transition in controlling the elasticity of ultra high-$\nu$ glasses. To this aim, we show that our higher-$\nu$ computer glasses host relatively softer quasilocalized glassy excitations, and establish relations between their associated characteristic frequency, macroscopic elasticity, and mechanical disorder.