Enhanced mobility of dislocation network nodes and its effect on dislocation multiplication and strain hardening

TL;DR

This study reveals that enhanced mobility of dislocation network nodes significantly influences dislocation multiplication and strain hardening, bridging the gap between atomistic MD simulations and larger-scale DDD models.

Contribution

It introduces a new understanding of dislocation node mobility, improving DDD simulation accuracy by incorporating previously unrecognized nodal behaviors observed in MD.

Findings

Discrepancies between MD and DDD in predicting crystal strength are due to dislocation node behaviors.

Incorporating nodal mobility into DDD aligns its predictions with MD results.

Nodal motion affects dislocation multiplication, recovery, and strain hardening processes.

Abstract

Understanding plastic deformation of crystals in terms of the fundamental physics of dislocations has remained a grand challenge in materials science for decades. To overcome this, the Discrete Dislocation Dynamics (DDD) method has been developed, but its lack of atomistic resolution leaves open the possibility that certain key mechanisms may be overlooked. By comparing large-scale Molecular Dynamics (MD) with DDD simulations performed under identical conditions we uncover significant discrepancies in the predicted strength and microstructure evolution in BCC crytals under high-strain rate conditions. These are traced to unexpected behaviors of dislocation network nodes forming at dislocation intersections, that can move in ways not previously anticipated as revealed by MD. Once these newfound freedoms of nodal motion are incorporated, DDD simulations begin to closely match plastic evolution observed in MD. This additional mechanism of motion whereby non-screw dislocations can change their glide plane profoundly affects fundamental processes of dislocation multiplication, recovery and storage that define strength of metals.