Indentation size effect in metallic glasses: Mean pressure at the initiation of plastic flow

Nanoindentation tests using a spherical indenter of tip radius 10 µm have been performed on Zr- and Pd-based metallic glasses, focusing on the cumulative distribution of the first yield load. When normalized using the macroscopic yield stress, the distribution of mean pressure at yield is nearly independent of the glass composition. Collecting literature data, there is a clear indentation size effect in metallic glasses: the smaller the indenter tip radius, the larger the indentation pressure at yield. The magnitude of the size effect in metallic glasses is compared with, and found to lie between, the cases of crystalline metals and ceramics.