# Pattern formation during deformation of metallic nanolaminates

## TL;DR

This study uses molecular dynamics simulations to explore how metallic nanolaminates deform, revealing vortex pattern formation linked to grain rotation and interface roughness, which impacts material behavior during shear.

## Contribution

It uncovers the mechanism of vortex formation during shear deformation in metallic nanolaminates, highlighting the role of interface roughness and grain rotation, a novel insight into deformation patterns.

## Key findings

- Vortex patterns form when interfaces are atomically rough.
- Pattern formation is linked to grain rotation caused by dislocation hindrance.
- Shear-softening occurs alongside vortex formation.

## Abstract

We used nonequilibrium molecular dynamics simulations to study the shear deformation of metallic composites composed of alternating layers of Cu and Au. Our simulations reveal the formation of "vortices" or "swirls" if the bimaterial interfaces are atomically rough and if none of the {111} planes that accommodate slip in fcc materials is exactly parallel to this interface. We trace the formation of these patterns back to grain rotation, induced by hindering dislocations from crossing the bimaterial interface. The instability is accompanied by shear-softening of the material. These calculations shed new light on recent observations of pattern formation in plastic flow, mechanical mixing of materials and the common formation of a tribomutation layer in tribologically loaded systems.