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MM: Metall- und Materialphysik

MM 5: Phase transitions II

MM 5.1: Vortrag

Montag, 27. März 2006, 11:45–12:00, IFW D

Formation of competing γ-Fe and φ-phase in undercooled Nd-Fe-B alloys investigated by in-situ diffraction experiments using synchrotron radiation — •Thomas Volkmann¹, Joern Strohmenger², Oliver Heinen¹, Dirk Holland-Moritz¹, Jianrong Gao³, Sven Reutzel², and Dieter M. Herlach¹ — ¹Institut für Raumsimulation, Deutsches Zentrum für Luft- und Raumfahrt (DLR), D-51170 Köln, Germany — ²Institut für Experimentalphysik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany — ³Key Lab of Electromagnetic Processing of Materials, Northeastern University, Shenyang 110004, P.R. China

Nd-Fe-B alloys are used for the development of advanced permanent magnets that are based on the Nd₂Fe₁₄B₁-phase (φ-phase). Under equilibrium solidification conditions of alloys near the stoichiometric composition the φ-phase is formed by a peritectic reaction from pro-peritectic γ-Fe. The electromagnetic levitation technique was combined with the diagnostic means at the European Synchrotron Radiation Facilitiy (ESRF) to study in-situ phase formation in the undercooled melt by energy dispersive diffraction experiments during solidification. It was found that the γ-Fe-phase crystallizes primarily in the undercooled melt even at temperatures below the peritectic temperature at which γ-Fe is metastable while the stable φ-phase solidifies in a subsequent step.

The work was financially supported by the Deutsche Forschungsgemeinschaft under contract no. HE1601/14. The support from the ESRF in Grenoble is gratefully acknowledged.