Stress field modification near linear complexions increases the effective obstacle size and strengthening effect

TL;DR

This study uses molecular dynamics simulations to reveal how linear complexions modify stress fields and enhance strengthening in alloys, providing insights for designing stronger materials.

Contribution

It demonstrates that linear complexions can significantly strengthen alloys by stress field modification, beyond direct particle interactions, and identifies key orientation effects.

Findings

Both nanoparticle and platelet complexions increase strength.

Stress field modification restricts dislocation motion.

Particle-dislocation orientation greatly influences resistance.

Abstract

Linear complexions are stable defect states that form along dislocations and recent experiments have demonstrated strengthening effects exceeding classical precipitation hardening predictions, motivating a detailed study of nanoscale strengthening mechanisms. Here, molecular dynamics simulations in Al-Cu and Ni-Al face-centered cubic alloys are used to demonstrate distinct plasticity mechanisms associated with linear complexions. Both nanoparticle array and platelet array complexions exhibit appreciable strengthening. In addition to direct interactions with the particles, stress field modification in nearby regions can restrict dislocation motion as well. Finally, the relative particle-dislocation orientation is found to have a large effect, with the strongest resistance observed when the dislocation stress field aligns with the original complexion nucleation condition. As a whole, these findings provide mechanistic insight into the strengthening observed experimentally and establish design principles for linear complexion-induced strengthening in structural alloys.