Atomistic study of hardening mechanism in Al-Cu nanostructure

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 sizes on the hardening mechanism of an Al-Cu nanostructure is elucidated by molecular dynamics simulation. The 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 rates using embedded atom method (EAM) potential at a temperature of 50~500 K. It is found that the failure mechanism of the nanostructure is governed by the temperature, grain size, and strain rate applied. At the high temperature of 300–500 K, the failure strength of the 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 in 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 sizes to show how the dislocation affects the material properties at the nanoscale. These results will further aid investigation on the deformation mechanism of other nanostructures.