Pronounced nanoindentation creep deformation in Cu-doped CoFe-based metallic glasses

By using nanoindentation techniques combined with atomic force microscopy, a pronounced creep behavior at ambient temperature as demonstrated by small creeping stress exponents was observed in (Co_0·7Fe_0.3)_0.68B_0·219Si_0·051Nb_0.05 metallic glass with 0.5 at.% Cu addition. Such obvious creep deformation is due to the precipitation of Co(Fe)-rich clusters induced by the chemical effect of Cu. It promotes the formation of the weakly bonded structure and thereby the generation of plenty of excess free volume during the nucleation and propagation of multiple shear bands in the process of deformation, which contributes to a steady creep behavior and large plasticity. Our work provides a microscopic understanding of creep behaviors in Cu-doped metallic glasses, which might also guide for improving the plasticity of these alloys.