Indentation size effect for spherical nanoindentation on nanoporous gold

Abstract

We find that the indentation size effect (ISE) occurs during spherical indentation on nanoporous gold (np-Au). The hardness increases as the indenter radius decreases at a fixed representative strain. We prepare np-Au samples with a ligament size of 26 nm by free-corrosion dealloying and perform multiple spherical nanoindentations with nominal indenter radii of 4, 12, and 50 μm. A nanomechanics model for the ISE during spherical indentation is developed, and the model accurately describes the hardness depending on the indenter radius. We also correlate the ISE trends of spherical and Berkovich indentations along with their differences in terms of the representative strain and the indentation work.