Impact of high pressure on reversible structural relaxation of metallic glass

TL;DR

This study theoretically explores how high pressure influences the reversible structural relaxation and dynamics of metallic glasses, revealing pressure-induced metastable states and a fragile-to-strong transition.

Contribution

It introduces a theoretical model accounting for metastable states under pressure, providing new insights into metallic glass relaxation behavior and dynamics.

Findings

Pressure creates metastable states affecting relaxation times.

Reversible relaxation time significantly decreases with pressure when metastable states are considered.

External compression induces a fragile-to-strong transition in metallic glasses.

Abstract

We theoretically investigate the temperature dependence of the reversible structural relaxation time and diffusion constant of metallic glasses under pressure. The compression not only changes the glassy dynamics, but also generates a metastable state along with a higher-energy state where the system can rejuvenate. The relaxation times for forward and backward transitions in this two-state system are nearly identical and much faster than the relaxation time without accounting for barrier-recrossing. At ambient pressure, the expected irreversible relaxation process is recovered, and our numerical results agree well with prior experimental results. An increase of pressure has a minor effect on the relaxation time and diffusion constant that one computes without considering the influence of the metastable state, but it leads to a large reduction of the reversible relaxation time computed upon taking the metastable state into account. The presence of external compression is also shown to trigger a fragile-to-strong crossover in metallic glasses.