Viscoelasticity of Cu- and La-based bulk metallic glasses: Interpretation based on the quasi-point defects theory

The dynamic mechanical relaxation of metallic glasses is closely associated with the physical and mechanical properties. In the current work, the dynamic mechanical relaxation behaviors of Cu46Zr45Al7Y2 and La65Al14(Cu5/6Ag1/6)11(Ni1/2Co1/2)10 bulk metallic glasses are investigated by mechanical spectroscopy. In general, metallic glasses display two relaxation modes: main (α) relaxation and the slow secondary (β) relaxation. The α relaxation is linked to the dynamic glass transition phenomenon and viscous flow while the slow β relaxation is associated with many fundamental issues, such as diffusion and glass transition phenomenon. The experimental study shows La65Al14(Cu5/6Ag1/6)11(Ni1/2Co1/2)10 bulk metallic glass displays a noticeable slow β relaxation. Contrarily, the Cu46Zr45Al7Y2 bulk metallic glass relaxation process takes the form of an “excess wing”. In the framework of quasi-point defects (QPD) theory, the dynamic mechanical response of the metallic glasses is discussed.