Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 52: Phase Transformations I
MM 52.3: Talk
Thursday, March 14, 2013, 10:45–11:00, H26
Investigation of solidification dynamics of Zr-based alloys — •Raphael Kobold1,2 and Dieter Herlach1,2 — 1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany — 2Ruhr-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 Zr-based alloys such as CuZr, NiZr and NiZrAl with Zirconium concentrations ranging from 36 to 64 at.% including eutectic and intermetallic phases. We use electrostatic levitation technique to melt and undercool samples with a diameter of 2-3 mm under ultra-high-vacuum conditions. 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 recorded by using a high-speed camera with a maximum rate of 50.000 frames per second and are analyzed with a software for optical ray tracing. Furthermore, we try to model the growth velocity vs. the undercooling temperature and perform sample EBSD analysis with a scanning electron microscope. This project is funded by Deutsche Forschungsgemeinschaft, under grant HE1601/26-1.