Nanoindentation study on elastic and plastic anisotropies of Cu single crystals

The elastic and plastic anisotropies of three oriented Cu single crystals were determined by a nanoindentation technique with a Berkovich and a cube-corner indenter, respectively. The indentation modulus ( E) of the crystals in the elastic and the plastic regimes were separately extracted using Hertzian elastic analysis and the Oliver-Pharr (O&P) method [J. Mater. Res. 7 1564 ( 1992)]. E values for Cu( 111) and ( 110) are nearly identical, about 20% larger than that of ( 001), as determined using a Berkovich tip in both regimes. E values determined in the plastic regime using a Berkovich tip agree well with theoretical predictions in terms of the Vlassak and Nix [ Phil. Mag. A 67 1065 ( 1993); J. Mech. Phys. Solids 42 1223 ( 1994)] analytical method, but smaller than those determined in the elastic regime. Elastic anisotropies in the plastic regime, however, are not measurable as a cube-corner indenter was used. The hardness ( H) of Cu crystals exhibits an obvious indentation size effect and larger H values are obtained with a sharper indenter.