Decoupling of Component Diffusion in a Glass-Forming Zr46.75Ti8.25Cu7.5Ni10Be27.5 Melt Far above the Liquidus Temperature.

We report Zr95 and 57Co radiotracer diffusivities and viscosity data in the equilibrium liquid state of a bulk metallic glass forming Zr46.75Ti8.25Cu7.5Ni10Be27.5 melt (Vitreloy 4) far above the liquidus temperature Tl that are not affected by convection, as evidenced via quasielastic neutron scattering. Zr diffusion is strongly decoupled from diffusion of the smaller components by more than a factor of 4 at Tl, although it obeys the Stokes-Einstein equation. The results suggest that, in the present Zr-based metallic glass forming systems, diffusion and viscous flow start to develop solidlike, i.e., energy-landscape-controlled, features already in the stable liquid state more than 300 K above the mode coupling temperature Tc. [ABSTRACT FROM AUTHOR]