Atomic diffusion mechanisms in a binary metallic melt

¹  Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR) 51170 Köln, Germany, EU
²  Physik-Department E13, Technische Universität München - 85747 Garching, Germany, EU
³  Institut Laue-Langevin - BP 156, 38042 Grenoble Cedex 9, France, EU
⁴  Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München 85747 Garching, Germany, EU

Corresponding author: thomas.voigtmann@dlr.de

Received: 21 February 2008
Accepted: 22 April 2008

Abstract

The relation between static structure and dynamics as measured through the diffusion coefficients in viscous multicomponent metallic melts is elucidated by the example of the binary alloy Zr₆₄Ni₃₆, by a combination of neutron-scattering experiments and mode-coupling theory of the glass transition. Comparison with a hard-sphere mixture shows that the relation between the different self diffusion coefficients strongly depends on chemical short-range ordering. For the Zr-Ni example, the theory predicts both diffusivities to be practically identical. The kinetics of concentration fluctuations is dramatically slower than that of self-diffusion, but the overall interdiffusion coefficient is equally large or larger due to a purely thermodynamic prefactor. This result is a general feature for non-demixing dense melts, irrespective of chemical short-range order.