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MM: Fachverband Metall- und Materialphysik

MM 38: Liquid and Amorphous Metals

MM 38.5: Vortrag

Mittwoch, 28. März 2012, 16:00–16:15, H 1029

Investigation of solidification dynamics of undercooled melts of Cu-Zr alloys — •Raphael Kobold¹, Dieter Herlach^1,2, and Ulrich Köhler² — ¹Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany — ²Institut für Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany

In contrast to experiments with most undercooled binary alloys the velocity of dendritic growth of a Cu₅₀Zr₅₀ alloy does not increase monotonically with undercooling but passes through a maximum and then decreases. To study this behaviour we investigate Cu-Zr alloys with Zirconium concentrations ranging from 44 to 54 at.% including eutectic and intermetallic phases. We use electrostatic levitation technique to melt and undercool samples with a diameter of 2-3mm under ultra-high-vacuum. Containerless processing is an effective tool for undercooling metallic melts far below their equilibrium melting temperatures since heterogeneous nucleation on container walls is completely avoided. During crystallisation of the undercooled melt the heat of crystallisation is released. The rapid increase of the temperature at the solid-liquid interface makes the solidification front visible. The velocities of the solidification front are measured by using a high-speed camera with a maximum frame rate of 50 000 pictures per second. Furthermore, experiments for phase selection during rapid solidification of the undercooled Cu-Zr melts were performed at DESY Hamburg.