Anisotropic effects in elastic and incipient plastic deformation under (001), (110), and (111) nanoindentation of Al and Cu

Atomistic simulations of (001), (110), and (111) nanoindentation are performed to investigate anisotropic effects in elastic and incipient plastic behavior under nanoindentation. We compared two materials, single-crystalline Al and Cu, focusing on the large difference between their anisotropic properties. The indent load-depth behavior of Al during elastic deformation exhibits slight anisotropy, while that of Cu varies greatly according to the indentation axis. In addition, incipient plastic deformation, that is, dislocation nucleation, depends largely on the predicted slip system. While dislocations are emitted on the surface when indented by a spherical indenter with small radius, collective dislocation emission occurs from within the material. In the case of dislocation emission within the material, the critical mean pressure, which is an important indicator of dislocation nucleation, is inherent to the indentation axis in both materials.

Figure 1

(Color online) Relationship between indent load and depth for three spherical indenters having different radii and three different indentation axes and the elastic solution.

Figure 2

(Color online) Distributions of von Mises equivalent stress for (001), (110), and (111) indentation in Al and Cu.

Figure 3

(Color online) Relationship between mean pressure and depth during indentation on three different planes by three spherical indenters, each having a different radius.

Figure 4

(Color online) Dislocation emission under (001), (110), and (111) nanoindentation by $r5$ and $r30\mathrm{nm}$ indenters, and diagrams of the activated slip systems (bold line) associated with Thompson tetrahedron.