Atomistic study of hardening mechanism in Al-Cu nanostructure

TL;DR

This study uses molecular dynamics simulations to explore how grain size, temperature, and strain rate influence the hardening and failure mechanisms of Al-Cu nanostructures, revealing size-dependent strengthening and failure behaviors.

Contribution

It provides new insights into the grain size and temperature effects on the hardening mechanism of Al-Cu nanostructures through detailed atomistic simulations.

Findings

Failure strength increases with decreasing grain size at high temperatures.

Dislocation motion is hindered by smaller grain sizes, contributing to hardening.

Failure initiates at weak Al grains and propagates via boundary mechanisms.

Abstract

Nanostructures have the immense potential to supplant the traditional metallic structure as they show enhanced mechanical properties through strain hardening. In this paper, the effect of grain size on the hardening mechanism of Al-Cu nanostructure is elucidated by molecular dynamics simulation. Al-Cu (50-54% Cu by weight) nanostructure having an average grain size of 4.57 to 7.26 nm are investigated for tensile simulation at different strain rate using embedded atom method (EAM) potential at a temperature of 50~500K. It is found that the failure mechanism of the nanostructure is governed by the temperature, grain size as well as strain rate effect. At the high temperature of 300-500K, the failure strength of Al-Cu nanostructure increases with the decrease of average grain size following Hall-Petch relation. Dislocation motions are hindered significantly when the grain size is decreased which play a vital role on the hardening of the nanostructure. The failure is always found to initiate at a particular Al grain due to its weak link and propagates through grain boundary (GB) sliding, diffusion, dislocation nucleation and propagation. We also visualize the dislocation density at different grain size to show how the dislocation affects the material properties at the nanoscale. These results will further aid investigation on the deformation mechanism of nanostructure.