Title: Atomistic study of hardening mechanism in Al-Cu nanostructure,
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.