Hamburg 2001 – wissenschaftliches Programm

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M: Metallphysik

M 33: Postersitzung

M 33.3: Poster

Donnerstag, 29. März 2001, 15:15–19:00, Foyer S4, CCH

Levitation Experiments on Peritectic NdFeB Melts — •Jianrong Gao^1,2, Thomas Volkmann^1,3, Bingbo Wei², and Dieter M. Herlach¹ — ¹Institut für Raumsimulation, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln — ²Department of Applied Physics, Northwestern Polytechnical University, Xian 710072, China — ³Institut für Experimentalphysik IV, Ruhr-Universität Bochum, D-44780 Bochum

NdFeB alloys are excellent permanent magnet materials. Their outstanding magnetic properties are known to come from the peritectic Nd₂Fe₁₄B compound. Due to relatively high coolings rates, however, the formation of this compound in as-cast ingots is often hindered by difficult atom diffusion. Recently, it was found that large undercooling can change the solidification path of peritectic NdFeB alloys very significantly, and therefore allows the direct crystallization of the peritectic Nd₂Fe₁₄B phase from a liquid phase. In the present work, a number of peritectic NdFeB alloys was processed using the electromagnetic levitation technique, and phase selection in undercooled bulk melts was then investigated so as to determine the critical undercooling levels where the primary phase changes from one to another. In additon, the related phase selection mechanism was also analyzed using the current theories on nucleation and growth in undercooled melts.
Financial support from the Alexander von Humboldt Foundation (J.G.) and Deutsches Zentrum für Luft- und Raumfahrt DLR under contract No. 50 WM 9930 (T.V.) is gratefully acknowledged.