Structure and Strength of Dislocation Junctions: An Atomic Level Analysis

TL;DR

This paper uses atomic-level simulations to analyze the structure and strength of dislocation junctions, revealing the unzipping failure mechanism and the influence of initial dislocation orientations, which are often overlooked in macroscopic models.

Contribution

It provides the first atomic-level insight into the dislocation junction breaking process and highlights the importance of initial dislocation directions.

Findings

Junctions are destroyed by an unzipping mechanism.

Critical stress for junction breaking matches line tension model predictions.

Initial dislocation orientations significantly affect the breaking process.

Abstract

The quasicontinuum method is used to simulate three-dimensional Lomer-Cottrell junctions both in the absence and in the presence of an applied stress. The simulations show that this type of junction is destroyed by an unzipping mechanism in which the dislocations that form the junction are gradually pulled apart along the junction segment. The calculated critical stress needed for breaking the junction is comparable to that predicted by line tension models. The simulations also demonstrate a strong influence of the initial dislocation line directions on the breaking mechanism, an effect that is neglected in the macroscopic treatment of the hardening effect of junctions.