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MM: Fachverband Metall- und Materialphysik

MM 23: Topical Session Heterogeneous Nucleation and Initial Evolution of Microstructure - Poster

MM 23.4: Poster

Dienstag, 24. März 2009, 14:45–16:30, P4

Surface Tension of Liquid Al-Cu Alloys — •Julianna Schmitz, Jürgen Brillo, and Ivan Egry — Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany

Precise surface tension data of liquid Al-Cu alloys are fundamental for our purpose of studying the interaction of the liquid with differently oriented single crystalline sapphire surfaces. These data were measured for the entire Al-Cu liquid alloy system as a function of temperature and composition. Contamination of the sample from contact with container walls had to be avoided. Thus, measurements were performed in an inert gas atmosphere using an electromagnetic levitation furnace. From surface oscillations of the levitated droplet the surface tension was determined by means of the oscillating drop method. Hence, we obtained precise data of the entire Al-Cu system within a wide temperature range with only a small scatter of 3%. A linear temperature dependence with a negative slope was found for all stoichiometric compositions whereas the surface tension monotonically decreases with increasing aluminium concentration. The observed behaviour with respect to both, temperature and concentration, is in agreement with thermodynamic model calculations using the regular solution approximation. Additionally, we give an outlook on the measurement of contact angles and the work of adhesion as a function of the crystalline substrate orientation performed with a sessile drop apparatus whose construction is about to be finished. Combining this with the surface tension data we are able to estimate solid-liquid interfacial energies.