Exploring the relation between transonic dislocation glide and stacking fault width in FCC metals

TL;DR

This study uses molecular dynamics simulations to explore how dislocation core structures and stacking fault widths influence the ability of edge and screw dislocations to reach transonic speeds in FCC metals under high stress.

Contribution

It systematically links dislocation core structures and stacking fault widths to transonic dislocation mobility in FCC metals, highlighting the role of relativistic effects.

Findings

Edge dislocations more likely to reach transonic speeds than screw dislocations.

Dislocation core structure influences transonic velocity capability.

Stacking fault width variations are linked to relativistic effects near limiting velocities.

Abstract

Theory predicts limiting gliding velocities that dislocations cannot overcome. Computational and recent experiments have shown that these limiting velocities are soft barriers and dislocations can reach transonic speeds in high rate plastic deformation scenarios. In this paper we systematically examine the mobility of edge and screw dislocations in several face centered cubic (FCC) metals (Al, Au, Pt, and Ni) in the extreme large-applied-stress regime using MD simulations. Our results show that edge dislocations are more likely to move at transonic velocities due to their high mobility and lower limiting velocity than screw dislocations. Importantly, among the considered FCC metals, the dislocation core structure determines the dislocation's ability to reach transonic velocities. This is likely due to the variation in stacking fault width (SFW) due to relativistic effects near the limiting velocities.