Dresden 2003 – scientific programme
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M: Metallphysik
M 18: Symposium: Phasenumwandlungen in Schmelzen VII
M 18.2: Talk
Tuesday, March 25, 2003, 15:00–15:15, IFW A
Microstructure of Nd-Fe-B alloys influenced by the melt hydrodynamics — •Regina Hermann1, Octavian Filip1, Gunther Gerbeth2, and Janis Priede2 — 1Institute for Solid State and Materials Research (IFW) Dresden — 2Forschungszentrum Rossendorf e.V., Dresden
The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated using the electromagnetic levitation technique, forced rotation experiments and the application of alternating magnetic fields. The electromagnetic levitation technique, which allows the in-situ measurement of the solidification kinetics containerlessly, has been used in order to investigate the influence of the internal melt motion on the microstructure formation of Nd-Fe-B alloys, mainly with respect to the volume fraction and grain size of the α-Fe phase. Moreover, experiments where specially sealed samples were subjected to a well-defined forced rotation have been carried out. The determination of the α-Fe volume fraction by measuring the magnetic moment in a vibrating sample magnetometer (VSM) resulted in a distinct reduction of the α-Fe volume fraction in samples with strong rotation. The influence of the cooling rate and the undercooling level on the microstructure formation and phase distribution has been investigated as well. Furthermore, a new category of experiment has been started where a tailored magnetic field was applied in order to study the microstructure evolution due to an enhancement or suppression of the melt convection by additional alternating magnetic fields.