Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 13: Magnetic Materials

MA 13.7: Vortrag

Montag, 26. März 2012, 16:30–16:45, H 0112

Coercivity enhancement in nanocrystalline NdFeB hot pressed magnets by means of DyF₃ — •Simon Sawatzki¹, Martina Moore¹, Juliane Thielsch¹, Ludwig Schultz¹, and Oliver Gutfleisch^2,1 — ¹IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany — ²TU Darmstadt, Institute of Material Science, Petersenstrasses 23, D-64287 Darmstadt, Germany

In order to address the strategic resource problems related to permanent magnet’s development for electro motors the specific modification of the grain boundary by the heavy rare earth Dy is a possible solution. For that reason the magnets have been prepared by means of hot pressing Nd-rich melt-spun ribbons of MQU-F type. The treatment with DyF₃ powder was done in two ways: (a) by coating the compact magnet with DyF₃ and subsequent annealing and (b) by mixing DyF₃ with the melt-spun powder and subsequent hot pressing at 725^∘C. Permagraph measurements have been carried out to characterize the magnetic properties whereas the microstructure was investigated with high-resolution scanning electron microscopy.

The coating and annealing, route (a), was shown not be useful as diffusion of Dy out of the dried slurry on to top of the magnet into the volume was very limited. Route (b) however results in magnets with optimized coercivities in dependency of the fluoride concentration. The most promising stoichiometry contains 1.15 wt% Dy and leads to an improvement in coercivity of 10 % compared to the unmodified hot compacted magnet with a largely unchanged remanence.