# Brittle-Ductile Transitions in a Metallic Glass

## TL;DR

This paper uses shear-transformation-zone theory to analyze how initial disorder affects brittle-ductile transitions in metallic glasses, revealing a sudden shift from brittle to ductile failure linked to plastic zone dynamics.

## Contribution

It provides a theoretical framework explaining the brittle-ductile transition in metallic glasses based on initial disorder and plastic zone behavior.

## Key findings

- Plastic zone shields the notch tip initially.
- Sudden breakdown of the plastic zone causes brittle-ductile transition.
- Theoretical predictions align with experimental observations.

## Abstract

Recent computational and laboratory experiments have shown that the brittle-ductile transitions in metallic glasses such as Vitreloy1 are strongly sensitive to the initial effective disorder (or "fictive") temperature. Glasses with lower effective temperatures are weak and brittle; those with higher effective temperatures are strong and ductile. The analysis of this phenomenon presented here examines the onset of fracture at the tip of a slightly rounded notch as predicted by the shear-transformation-zone (STZ) theory of spatially varying plastic deformation. The central ingredient of this analysis is an approximation for the dynamics of the plastic zone formed by stress concentration at the notch tip. This zone first shields the tip but then breaks down suddenly producing a discontinuous transition between brittle and ductile failure, in agreement with the numerical and experimental observations.