Nano-indentation tests were performed on Ni3Al and the dense dislocation zones beneath the nano-indents were examined by transmission electron microscopy. The size of these dense dislocation zones was found to be significantly larger than the Oliver-Pharr contact size especially at small indentation depths. The results support an earlier suggestion that the densely dislocated core of a nano-indent relaxed to give rise to a reduction of the measured hardness from the simple Nix-Gao prediction.

TEM Measurement of Nanoindentation Plastic Zones in Ni3Al. Wo, P.C., Ngan, A.H.W., Chiu, Y.L.: Scripta Materialia, 2006, 55[6], 557-60