A study on the evolution of subsurface deformation in a Zr-based bulk metallic glass during spherical indentation

Abstract

Due to its several advantages, including a simple testing procedure and the use of a small volume of material, the instrumented indentation technique has been widely performed to elucidate the characteristics of plasticity in bulk metallic glasses (BMGs) which typically show very different deformation behaviour from that of crystalline counterparts. As an effort to shed additional light on the topics, here we examined the inhomogeneous plastic deformation of a Zr-Cu-Ni-Al-Ti BMG by performing both macroscopic instrumented indentation (with a spherical indenter) and nanoindentation (with a three-sided pyramidal Berkovich indenter) on the interface-bonded sample as well as on a bulk sample. Especially, we put emphasis on analysing the evolution of shear-band-ruled deformation generated underneath the indenter during spherical indentation. It was revealed that the inter-band spacing and the shear band density are independent of indentation load and thus stress level. Furthermore, subsequent performance of nanoindentation showed that the subsurface region under the indenter was indeed softened and had quite different deformation characteristics from that of the un-deformed region.