Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster session
MM 20.18: Poster
Dienstag, 27. März 2007, 14:45–18:00, Poster C
In-situ Observation of Phase Formation in Undercooled Nd-Fe-B-melts with Synchrotron Radiation and High-Speed Video Analysis — •Jörn Strohmenger1,2, Thomas Volkmann2, Jianrong Gao3, Sven Reutzel1,2, Dirk Holland-Moritz1, Oliver Heinen1, and Dieter Herlach1 — 1Institut für Materialphysik im Weltraum, Deutsches Zentrum f. Luft u. Raumfahrt, 51170 Köln — 2Institut für Experimentalphysik IV, Ruhr-Universität Bochum, 44780 Bochum — 3Key Lab of Electromagnetic Processing of Materials, Northeastern University Shenyang, 110004, P.R. China
Competitive crystallisation of stable and metastable phases in undercooled Nd-Fe-B melts was investigated using electromagnetic levitation technique combined with in-situ X-ray diffraction experiments at the ESRF. It is shown that the primary crystallizing phase is influenced by undercooling, e.g a metastable phase can be directly observed which initiates the formation of the intermetallic Phi-phase. It can be identified as a ternary extension of the rhombohedral Nd2Fe17 phase being stable in binary Nd-Fe alloys. The growth velocity of Phi-phase is determined with a high-speed camera sytem.It is shown that growth velocity is affected by induced melt convection. A phase selection diagram showing the different solidification pathways as a function of undercooling and alloy composition will be analyzed within theories of nucleation and crystal growth. This work was supported by DFG under contract No. HE1601/14.