Gamma relaxation in bulk metallic glasses

TL;DR

This paper reports the discovery of a third relaxation mechanism, called gamma-relaxation, in bulk metallic glasses, which involves low-energy atomic rearrangements causing macroscopic rejuvenation, observed across different alloys.

Contribution

It introduces gamma-relaxation as a new, general relaxation process in metallic glasses, distinct from alpha and beta relaxations, driven by thermal stresses during cooling.

Findings

Gamma-relaxation observed in three different metallic alloys.

It causes macroscopic rejuvenation through atomic rearrangements.

Identified as a general process in metallic glasses.

Abstract

Studying the primary {\alpha}- and secondary {\beta}-relaxation process has contributed significantly to the understanding of the structure and rheology of metallic glasses. In this letter, we report on a third relaxation mechanism indicated by a maximum in the loss modulus at low temperatures, which we term {\gamma}-relaxation. Contrary to the {\alpha}- and {\beta}-relaxation mechanisms, this irreversible, low energy excitation causes a macroscopic rejuvenation, which we assign to non-affine atomic rearrangements in the matrix that are driven by thermal stresses during cooling. Observed in three different glassy alloys, the low temperature relaxation is identified as a general process in metallic glasses.