Crystalline plasticity on copper (001), (110), and (111) surfaces during nanoindentation

Molecular dynamics (MD) simulations are performed to study crystalline plasticity during nano-indentation by comparing the elastic-plastic response of three copper substrates with surfaces (001), (110), and (111) crystallographic planes. The effects of elastic anisotropy and crystallographic symmetry on the reduced modulus, dislocation nucleation, and subsequent microstructure evolution, are investigated. The reduced modulus of (111) surface is found to be the largest, while that of (001) surface is the smallest. Elastic stress distribution calculated from finite element method (FEM) is qualitatively consistent with the MD simulation results. Significant differences exist in the deformation behavior in the three different crystallographic orientations. The differences in the load-displacement curves for the three different cases are correlated with those in the corresponding evolutions of the underlying dislocation structure. Yielding platforms exist typically in load-displacement curve of Cu (001), which can be attributed to effective resistance of dislocation locks. Load drops are typically characteristic of Cu (111) and (110), due to a more mobile dislocation structure.