Liquid Al80Cu20: Atomic diffusion and viscosity

Properties of mass transport in liquid Al80Cu20 were measured over a broad temperature range of more than 500 K by means of oscillating cup viscometry and quasielastic neutron scattering. The shear viscosity and the coefficient of the Cu self-diffusion exhibit an Arrhenius-type temperature dependence. The activation energy for the viscous flow is 2.4 times smaller than that of the Cu self-diffusion. Below 1400 K, the Cu self-diffusion becomes increasingly smaller than expected from the viscosity data rescaled via the Stokes–Einstein relation.