Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 11: Microstructure and Phase Transformations II - Nucleation/Solidification
MM 11.4: Vortrag
Montag, 31. März 2014, 12:15–12:30, IFW B
Dendritic growth of tenfold twins from an undercooled melt of NiZr — •Raphael Kobold1,2, Wolfgang Hornfeck1, Matthias Kolbe1, and Dieter Herlach1,2 — 1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany — 2Ruhr-Universität Bochum, 44780 Bochum, Germany
The solidification of the intermetallic, congruent melting binary alloy Ni50Zr50 is studied in a temperature regime between the melting and the glass transition temperature. This system is well known as a good glass former in a broad concentration range of 30 to 80 at.% Zr. It is studied as a glass forming material, but it has as well a rare behaviour in solidification. 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 the rapid increase of the temperature at the solid-liquid interface makes the solidification front visible. The solidification front is recorded by using a high-speed camera with a frame rate of 10.000 (1024x744) frames per second. At high undercoolings the solidification front of Ni50Zr50 shows features which make the investigation of its solidification behaviour particularly interesting. We observed the growth of a solidification front with 10-fold symmetry at a high undercooling temperature of approximately 300 K and a cooling rate of 53 K/s. Funding by Deutsche Forschungsgemeinschaft, under grant HE1601/18.