Berlin 2008 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 9: SYM Phase Transformations in Metallic Melts III
MM 9.2: Talk
Monday, February 25, 2008, 15:15–15:30, H 1058
Influence of thermodynamic forces on diffusion in metallic melts measured by ex-situ and in-situ capillary techniques — •Axel Griesche1,2, Michael-Peter Macht2, and Günter Frohberg3 — 1Institut für Materialphysik im Weltraum, DLR, Linder Höhe, 51170 Cologne — 2Dept. Materials, Hahn-Meitner-Institute Berlin, Glienicker Str. 100, 14109 Berlin — 3Institute of Material Sciences and Technology, Technical University Berlin, Hardenbergstr. 36, 10623 Berlin
The Darken relation that correlates interdiffusion coefficients, self diffusion coefficients and thermodynamic factors was studied in different metallic melts. Interdiffusion and self diffusion in Al80Ni20, Al77Ni20Ce3 and Pd40Cu15Ni25P20 melts have been measured above the liquidus temperature using classical capillary methods and a novel X-ray radiography method. The chemical diffusion profiles of the ex-situ technique were determined by means of EDS whereas for the in-situ technique the profiles were determined from absorption pictures. Self diffusion coefficients were determined from penetration profiles of stable enriched 62Ni, 142Ce, 108Pd, and 65Cu isotopes measured by ICP-MS and for Ni additionally by QNS. The thermodynamic factors of Al-based alloys were calculated from chemical potential data whereas the thermodynamic factor of Pd-alloys was estimated from partial mixing enthalpies. In liquid Al alloys the enhancement of chemical diffusion with respect to self diffusion correlates linearly with the thermodynamic factor. For Pd alloys the experimental findings are discussed only qualitatively.