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M: Metallphysik

M 18: Symposium: Phasenumwandlungen in Schmelzen VII

M 18.5: Vortrag

Dienstag, 25. März 2003, 15:45–16:00, IFW A

Phase formation in undercooled Nd-Fe-B melts under reduced gravity during parabolic flights — •Sven Reutzel^1,2, Thomas Volkmann², Jörn Strohmenger², Jianrong Gao^2,3, Heinrich Bach¹, Dieter M. Herlach², and Takeshi Okutani⁴ — ¹Institute of Experimental Physics, Ruhr-University of Bochum, Germany — ²Institute of Space Simulation, German Aerospace Center (DLR), Köln, Germany — ³Department of Applied Physics, Nortwestern Polytechnical University, Xian, P.R. China — ⁴Institute for Materials and Chemical Processes, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

Crystallization behavior of undercooled Nd-Fe-B melts is investigated by electromagnetic levitation under conditions of reduced gravity during parabolic flights with respect to the phase formation of γ-Fe and the intermetallic compound Nd₂Fe₁₄B₁. The aim of the experiments is to elucidate the influence of fluid flow in the melt on crystallization kinetics of the different solid phases and hence the evolution of the microstructure. Electromagnetic processing on ground causes high convection speeds of the order of 1 m/s that are significantly reduced under microgravity conditions. During parabolic flight experiments the sample is processed and solidified containerlessly using the TEMPUS facility (Tiegelfreies elektromagnetisches Prozessieren unter Schwerelosigkeit) leading to a reduced melt convection level in the sample. During the entire experiment cycle, i.e. heating, melting, cooling and solidification the temperature of the sample is recorded by a pyrometer. In addition, after the flight experiment the structural and the magnetic properties of the retrieved samples are analyzed. The results are compared to reference experiments that are performed in ground laboratory using a similar electromagnetic levitation facility.