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M: Metallphysik

M 18: Symposium: Phasenumwandlungen in Schmelzen VII

M 18.3: Vortrag

Dienstag, 25. März 2003, 15:15–15:30, IFW A

Phase formation in electromagnetically levitated Nd-Fe-B-melts investigated by diffraction experiments with synchrotron radiation — •Jörn Strohmenger¹, Thomas Volkmann¹, Jianrong Gao^1,2, Oliver Heinen¹, Dirk Holland-Moritz¹, Sandrine Schlutig³, Thomas Buslaps³, and Dieter M. Herlach¹ — ¹Institut für Raumsimulation, Deutsches Zentrum für Luft- und Raumfahrt (DLR), D-51170 Köln — ²Department of Applied Physics, Northwestern Polytechnical University, Xian 710072, China — ³European Synchrotron Radiation Facility (ESRF), BP 220, F-38043 Grenoble Cedex, France

Crystallisation behaviour of undercooled Fe-Nd-B melts with Nd-contents between 11.8 and 18.0 at.% Nd at a ratio of Nd/B=2/1 is investigated by the electromagnetic levitation technique with respect to the crystallisation of the γ-Fe-phase and of the ordered intermetallic compound Nd₂Fe₁₄B₁ (Φ). Samples of about 1.5g in mass are processed and undercooled containerlessly at cooling rates of 10K/s. The in-situ monitoring of phase selection is accomplished by energy-dispersive diffraction experiments using synchrotron radiation at the European Synchrotron Radiation Facility (ESRF) in Grenoble. Phase formation in Fe-Nd-B alloys is of special interest due to their application for hard magnetic materials. Under thermodynamic equilibrium conditions the solidification sequence is primary γ-Fe followed by the peritectic formation of the Nd₂Fe₁₄B₁ (Φ) phase. It is shown that crystallisation of the properitectic phase is suppressed in favour of the peritectic Φ-phase in the undercooled melt. Additionally, the crystallisation of a metastable phase in Nd-Fe-B melts is directly observed by dint of diffraction experiments during solidification.

Financial support by the Deutsche Forschungsgemeinschaft (DFG) under HE1601/14 and the ESRF is gratefully acknowledged.