Nanoindentation analysis of plasticity evolution during spherical microindentation of bulk metallic glass

Abstract

Unlike most of crystalline metals, metallic glasses are known to exhibit a fully-plastic behavior or work softening during mechanical deformation. To analyze the characteristics of the deformed region, here a series of instrumented micro- and nano-indentation experiments were performed on a Zr-based bulk metallic glass (BMG) with geometrically self-similar sharp indenter as well as spherical indenters. First, we performed instrumented micro-indentation tests with a spherical indenter on the bonded interfaces of the BMGs. Although adhesive (used for bonding the interfaces) might significantly affect the deformation mode by reducing the constraint, the evolution of subsurface plasticity during spherical indentation was clearly observed. Subsequently, the subsurface plasticity underneath the hardness impressions was systematically examined through nanoindentation. The results are discussed in terms of major change in mechanical responses of BMGs before and after indentation-induced deformation.