Linking Thermal History to Shear Band Interaction and Macroscopic Ductility in Metallic Glasses

TL;DR

This study uses molecular dynamics simulations to explore how thermal history influences shear band interactions in metallic glasses, revealing mechanisms that could improve their ductility by controlling shear band behavior.

Contribution

It provides a microscopic understanding of how quenching rates affect shear band interactions and ductility in metallic glasses, linking thermal history to mechanical performance.

Findings

Slowly quenched samples show larger shear band interaction distances.

Rapid quenching leads to high density of soft regions and weak inter-band coupling.

Slow quenching promotes shear band deflection and coalescence, enhancing ductility.

Abstract

Shear band propagation and interaction are critical to the mechanical performance of metallic glasses and are strongly governed by thermal history, yet their microscopic mechanisms remain unclear. Here, using molecular dynamics simulations combined with a state-of-the-art annealing protocol, we systematically investigate these behaviors in a model metallic glass across effective quenching rates spanning six orders of magnitude. Through a double-notch model, we show that the normalized interaction distance relative to the single shear band width is significantly larger in slowly quenched samples than in rapidly quenched ones. Atomic-scale analysis reveals that rapidly quenched samples exhibit a high density of pre-existing soft regions, which trigger correlated shear transformation zones through local vortex fields, resulting in propagation path locking and weak inter-band coupling. In contrast, slowly quenched samples exhibit enhanced structural heterogeneity and a right-shifted activation energy spectrum, promoting a single large-scale vortex field ahead of the shear band front. This field facilitates long-range stress transmission and induces shear band deflection, convergence, and coalescence, a transition resembling a "shielding effect" in fracture mechanics, where vortex-mediated disturbances destabilize the advancing shear band front. Our findings establish a direct microscopic connection between glass stability and shear-band-mediated plasticity and suggest that regulating shear band interactions offers a promising route to enhance the room-temperature ductility of metallic glasses.