Effects of hydrogen on the nanomechanical properties of a bulk metallic glass during nanoindentation

In this reported work, the effects of hydrogen on the nanomechanical properties of a Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glass were investigated. The experimental results demonstrated that the nanohardness of the subject material was significantly reduced as the hydrogen content in glass increased, which was caused by the induced softening from the presence of hydrogen as observed by a decrease in the elastic modulus of the glass. The flow serration of the load-displacement on the glass during nanoindentation gradually became smooth when the hydrogen content was high, which was similar to the nanoindentation loading rate effect. The transition in the flow serration was a distinct physical phenomenon, suggesting a change of in the character of plasticity. A single shear band couldn't accommodate the imposed strain rapidly enough, and consequently multiple shear bands must operate simultaneously. The electronic structure of the hydrogenated Zr₅₅Cu₃₀Ni₅Al₁₀ were measured by X-Ray photoemission spectroscopy (XPS). In comparison with their quaternary counterparts, the XPS spectra of the hydrogenated samples were characterized by a shift of the Zr and Al band to lower binding energies. These suggested that the presence of solute hydrogen atoms resulted in the occurrence of the valence electron transferring from the Zr 3d band to the Zr–H bonding state, which would weaken the surrounding metallic glass.