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MA: Fachverband Magnetismus
MA 24: Magnetic Materials I
MA 24.7: Talk
Wednesday, March 18, 2015, 11:15–11:30, H 0112
Effect of particle refinement and grain boundary diffusion process in hot-deformed Nd-Fe-B permanent magnets — •Simon Sawatzki1, Christian Kübel2, Semih Ener1, Imants Dirba1, and Oliver Gutfleisch1,3 — 1TU Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt, Germany — 2KIT, institute of Nanotechnology INT, P.O. Box 3640, 76021 Karlsruhe, Germany — 3IWKS Hanau, Fraunhofer-Projektgruppe für Wertstoffkreisläufe und Ressourcenstrategie, 63457 Hanau, Germany
The grain boundary diffusion process (GBDP) drastically increases the coercivity in sintered Nd-Fe-B magnets without losing much in remanent magnetization by using only a very small amount of Dy [1]. Here Nd-Fe-B melt-spun ribbons have been hot-compacted and die-upset together with low melting DyCu, DyNdCu and TbNdCu powders to enhance coercivity. In order to optimize the distribution of these eutectics within the sample, particle refinement has been applied by grinding as well as ball milling. For the ternary alloys a uniform distribution was observed with secondary electron microscopy, which was attributed to the lower melting point of DyNdCu and TbNdCu compared to DyCu. Additional annealing at 600∘C leads to a diffusion of Dy or Tb into the Nd-Fe-B flakes, which was observed by transmission electron microscopy. This diffusion modifies the grain boundary phase and thus further enhances coercivity without decreasing remanence. The highest coercivity was observed for TbNdCu. Following this, hot-compacted magnets have been die-upset in order to prepare textured magnets. [1] Park et al. Proc. 16th REPM (Sendai, Japan) (2000) p.257