Diffusion of Mass in Liquid Metals and Alloys - Recent Experimental Developments and New Perspectives

Despite its tremendous importance for the understanding of underlying mechanisms and for the input in modeling and simulation of processes alike, accurate experimental diffusion data in liquid metals and alloys are rare. Common techniques exhibit several drawbacks that in most cases prevent an accurate measurement of diffusion coefficients convective contributions during diffusion annealing are the most prominent ones. Recently, we advanced the field of liquid diffusion experiments through the use of quasielastic neutron scattering (QNS) on levitated metallic droplets for accurate measurements of self-diffusion coefficients in high-temperature metallic liquids. For the accurate measurement of interdiffusion coefficients we combine long-capillary experiments with an in-situ monitoring of the entire interdiffusion process by the use of X-ray and neutron radiography. These experiments are accompanied by diffusion experiments in space in order to benefit from the purely diffusive transport under microgravity conditions. Recent experimental results are discussed in the context of the relation of selfand interdiffusion (Darken’s equation) and of the relation of self-diffusion and viscosity (Stokes-Einstein relation). Keyword(s): liquid metals, self-diffusion, interdiffusion, long-capillary, shear-cell, X-ray radiography, quasielastic neutron scattering.