Indentation size effect of hardness of metallic glasses

It has been found that the hardness measured from different metallic glassy samples using the Oliver and Pharr scheme [Oliver WC, Pharr GM. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res 1992;7:1564-83] [1] shows an apparent indentation size effect (ISE), i.e., the hardness decreases as indentation depth increases. A similar ISE of the pile-up ratio has also been found. A ribbon glassy sample fabricated at a larger cooling rate shows larger pile-up and lower hardness value than a bulk glassy sample under the same conditions. The ISE of hardness can be effectively eliminated by taking into account the different pile-up ratios at different indentation depths.