Computational studies of the glass-forming ability of model bulk metallic glasses

TL;DR

This study uses molecular dynamics simulations to identify key parameters influencing the glass-forming ability of binary metallic glasses, providing insights into how composition and atomic interactions affect their formation.

Contribution

It introduces a computational approach to predict glass-formability of bulk metallic glasses based on key atomic parameters and mixture compositions.

Findings

Optimal atomic size ratio less than 0.92

Near 50:50 stoichiometry favors glass formation

Weaker attraction between small atoms enhances glass-forming ability

Abstract

Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate R_c below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing R_c, and thus good glass-formers possess small values of R_c. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change R_c significantly. These studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.