Interdependent linear complexion structure and dislocation mechanics in Fe-Ni

TL;DR

This study uses atomistic simulations to explore how linear complexion structures in Fe-Ni alloys influence dislocation motion, revealing a strong initial pinning effect and phase transformation mechanisms that affect mechanical behavior.

Contribution

It uncovers the interdependence between linear complexion structures and dislocation mechanics, highlighting a novel pinning mechanism and phase transformation effects in Fe-Ni alloys.

Findings

Strong initial pinning of dislocations by complexions

Weaker pinning after initial dislocation break-away

L10-to-B2 phase transformations within nanoparticles

Abstract

Using large-scale atomistic simulations, dislocation mechanics in the presence of linear complexions are investigated in an Fe-Ni alloy, where the complexions appear as nanoparticle arrays along edge dislocation lines. When mechanical shear stress is applied to drive dislocation motion, a strong pinning effect is observed where the defects are restricted by their own linear complexion structures. This pinning effect becomes weaker after the first dislocation break-away event, leading to a stress-strain curve with a profound initial yield point, similar to the static strain ageing behavior observed experimentally for Fe-Mn alloys with the same type of linear complexions. The existence of such a response can be explained by local diffusion-less and lattice distortive transformations corresponding to L10-to-B2 phase transitions within the linear complexion nanoparticles. As such, an interdependence between linear complexion structure and dislocation mechanics is found.