Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 3: SYM Phase Transformations in Metallic Melts II

MM 3.1: Vortrag

Montag, 25. Februar 2008, 11:45–12:00, H 1058

Thermophysical Properties of Liquid Ternary Metallic Alloys — Ivan Egry and •Jürgen Brillo — Institut für Materialphysik im Weltraum, DLR, 51170 Köln

Thermophysical properties of liquid metals are difficult to measure, but highly relevant, both from an application and a fundamental point of view. On one hand, they are required for quantitative modelling of industrial processes such as solidification and welding; on the other, they are sensitive indicators of ordering phenomena in the liquid phase. In binary and multicomponent alloys, the so called excess quantities are of particular interest. They describe the deviation of thermodynamic and thermophysical properties from the respective ideal mixing laws. In this project we have determined surface tensions and densities of the two ternary systems Cu-Fe-Ni and Ag-Al-Cu over the entire concentration range, including the limiting binary systems. The measurements have been performed on electromagnetically levitated liquid drops using non-contact diagnostic tools, like the oscillating drop technique for surface tension and a shadowgraph technique for density measurements. A wide temperature range, including the undercooled regime, was covered by the experiments. Surface tension data were modelled by the Butler equation using available Gibbs excess free energies, and generally good agreement was found. From the density data, the excess volumes were calculated. They constitute a non negligible contribution and can have either sign.