Morphology and mechanical properties of nanocrystalline Cu/Ag alloy

TL;DR

This study uses hybrid MC/MD simulations to explore how varying Ag concentrations affect the microstructure and mechanical properties of nanocrystalline Cu/Ag alloys, revealing critical concentrations that optimize flow stress.

Contribution

It provides new insights into the effects of Ag doping on grain boundary structures and deformation mechanisms in nanocrystalline Cu/Ag alloys.

Findings

Ag concentration influences grain boundary complexions and wetting layers.

Dislocation density decreases with more Ag, softening grain interiors.

A critical Ag level maximizes flow stress in the alloy.

Abstract

Hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations are conducted to study the microstructures of nanocrystalline (nc) Cu/Ag alloys with various Ag concentrations. When the Ag concentration is below 50 Ag atoms/nm!, an increase in Ag concentration leads to a gradual growth of monolayer grain boundary (GB) complexions into nanolayer complexions. Above the concentration of 50 Ag atoms/nm!, wetting layers with a bulk crystalline phase are observed. The effects of Ag on mechanical properties and deformation mechanisms of nc Cu/Ag alloys are investigated in MD simulations of uniaxial tension. GB sliding resistance is found to first increase and then decrease with an increase in Ag concentration. Surprisingly, we also find that the dislocation density decreases monotonically with an increase in Ag concentration, which suggests that the grain interiors are softened by the introduction of Ag dopants at GBs. In addition, there is a critical Ag concentration that maximizes flow stress of nc Cu/Ag alloys. The flow stress, GB sliding resistance, and the intragranular dislocation densities become less sensitive to Ag dopants when the grain diameter increases from 5nm to 40nm.