ABSTRACT

This paper presents a large-scale atomic resolution simulation of
nanoindentation into a thin aluminum film using the recently introduced
quasicontinuum method. The purpose of the simulation is to study the initial
stages of plastic deformation under the action of an indenter. Two different
crystallographic orientations of the film and two different indenter
geometries (a rectangular prism and a cylinder) are studied. We obtain both
macroscopic load versus indentation depth curves, as well as microscopic
quantities, such as the Peierls stress and density of geometrically necessary
dislocations beneath the indenter. In addition, we obtain detailed information
regarding the atomistic mechanisms responsible for the macroscopic curves. A
strong dependence on geometry and orientation is observed. Two different
microscopic mechanisms are observed to accommodate the applied loading:
(i) nucleation and subsequent propagation into the bulk of edge dislocation
dipoles and (ii) deformation twinning.