A connection between the structural alpha-relaxation and the beta-relaxation found in bulk metallic glass-formers

TL;DR

This paper investigates whether a known correlation between alpha- and beta-relaxations in molecular glasses also exists in metallic glasses, using experimental data from new La and Ce-based metallic glasses.

Contribution

It demonstrates that the correlation between alpha- and beta-relaxations applies to metallic glasses, extending the understanding of glass dynamics beyond soft matter.

Findings

The correlation between alpha- and beta-relaxations is confirmed in metallic glasses.

An explanation for the correlation in metallic glasses is provided.

The results may help understand properties like ductility and crystallization in metallic glasses.

Abstract

New metallic glasses containing La or Ce have been introduced that have dynamic properties bordering on extremes of conventional metallic glasses. This provides opportunity to test trends or correlations established before in molecular and polymeric glass-formers if exist the same exist in the broader family of metallic glasses. Due to the drastically different chemical and physical structure of metallic glass-formers than soft matter, there is no guarantee that any correlation found in the latter will hold in the former. If found, the result brings metallic glasses closer to the much wider classes of glass-formers by the similarity in properties, and possibly have the same explanation. In non-metallic glass-formers, a general and fundamental connection has been established between the non-exponentiality parameter of the structural alpha-relaxation and the separation between its relaxation time and the beta-relaxation time. In this paper we explore the experimental data of metallic glass-formers and show the correlation applies. An explanation of this correlation is given. The establishment of the correlation may facilitate the understanding of the roles played by the beta-relaxation observed in macroscopic properties of metallic glasses including the relations to shear transformation zone, ductile-brittle transition in deformation, crystallization, and diffusion.