Indentation of bulk metallic glasses: Relationships between shear bands observed around the prints and hardness

Indentation studies are conducted on two different bulk metallic glasses and for a variety of indenters: spherical, conical and pyramidal. Shear bands are observed around the prints for only some types of indenters and reasons for this are sought. Analytical models of hardness accounting or not for the pressure dependence of amorphous alloys and finite element analyses are used. It is shown that these bands are observed only when we leave the elastoplastic regime of indentation in favour of a fully plastic one. Important conclusions are drawn about hardness values. In metallic glasses, compared with, for example, crystalline alloys, because of their tremendous yield strains, determining the true hardness of a particular amorphous alloy is not straightforward; it depends on the correct choice of indenter.