We compare the experimental interdiffusion constants DAlCu in liquid Al81.3Cu18.7 at% to the experimental Cu self diffusion constants DCu in a similar Al80Cu20 at% melt. DAlCu are measured by an X-ray radiography technique and DCu are measured by the
quasielastic neutron scattering method. It was found that DAlCu is enhanced by a factor of 3 with respect to DCu. The relation between DAlCu and DCu is investigated in the context of Darken’s equation where the interdiffusion constant DAB in a binary A-B
system is approximated by a simple linear combination of the self diffusion constants DA and DB, DAB = (DAXB + DBXA)Φ (with XA and XB the mole fractions of A and B particles, respectively, and Φ the thermodynamic factor representing the thermodynamic driving force for interdiffusion). We also present a calculation of Φ from the Gibbs free energy data in molten Al-Cu. With these calculated Φ and the DCu data, interdiffusion coefficients in liquid Al-Cu have been calculated. However, the experimental DAlCu are larger than the calculated ones by a factor of 2. These results suggest that the enhancement of interdiffusion in Al-Cu liquids can not be only attributed to the thermodynamic driving force. Here we propose that the missing factor of about 2 in the Darken equation comes from the contribution of cross correlations to interdiffusion in Al-Cu liquids.
Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:15-qucosa-191501 |
Date | 11 December 2015 |
Creators | Zhang, Bo, Griesche, Axel, Meyer, Andreas |
Contributors | Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Materialphysik im Weltraum, Universität Leipzig, Fakultät für Physik und Geowissenschaften |
Publisher | Universitätsbibliothek Leipzig |
Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
Language | English |
Detected Language | English |
Type | doc-type:article |
Format | application/pdf |
Source | Diffusion fundamentals 11 (2009) 100, S. 1-8 |
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