Shear accelerated crystallization in a supercooled atomic liquid

TL;DR

This study demonstrates that applying shear flow to a supercooled metallic glass forming alloy accelerates its crystallization process, with the effect becoming significant above a critical shear rate, highlighting shear's role in atomic-scale phase transformations.

Contribution

It provides the first evidence of shear-accelerated crystallization in an atomic system at modest shear rates, linked to the material's high viscosity near the glass transition.

Findings

Shear flow reduces crystallization time during annealing.

Critical shear rate for acceleration is approximately 0.3 s$^{-1}$.

Shear effects are significant due to high viscosity near glass transition.

Abstract

A bulk metallic glass forming alloy is subjected to shear flow in its supercooled state by compression of a short rod to produce a flat disc. The resulting material exhibits enhanced crystallization kinetics during isothermal annealing as reflected in the decrease of the crystallization time relative to the non-deformed case. The transition from quiescent to shear-accelerated crystallization is linked to strain accumulated during shear flow above a critical shear rate $\dot\gamma_c\approx 0.3$ s$^{-1}$ which corresponds to P\'{e}clet number, $Pe\sim\mathcal{O}(1)$. The observation of shear accelerated crystallization in an atomic system at modest shear rates is uncommon. It is made possible here by the substantial viscosity of the supercooled liquid which increases strongly with temperature in the approach to the glass transition. We may therefore anticipate the encounter of non-trivial shear-related effects during thermoplastic deformation of similar systems.