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MA: Fachverband Magnetismus
MA 52: Magnetic Materials IV
MA 52.4: Vortrag
Freitag, 4. April 2014, 10:15–10:30, HSZ 403
Grain boundary modifications in hot-deformed Nd-Fe-B permanent magnets by low melting eutectics — •Simon Sawatzki1, Almut Dirks1, Florian Esdar1, Bianca Frincu1, Konrad Löwe1, and Oliver Gutfleisch1,2 — 1TU Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt, Germany — 2IWKS Hanau, Fraunhofer-Projektgruppe für Wertstoffkreisläufe und Ressourcenstrategie , 63457 Hanau, Germany
The grain boundary diffusion process (GBDP) drastically reduces the heavy rare earth Dy in sintered Nd-Fe-B magnets without losing much in remanent magnetization [1]. Here Nd-Fe-B melt-spun ribbons with optimized composition for hot workability have been hot-compacted together with low melting DyCu, DyNiAl, NdCu and NdAl powders to enhance coercivity. Annealing at 600°C leads to an interdiffusion of Dy and Nd at the interfaces between the Nd-Fe-B flakes and the Dy-rich phase that was visualized by high-resolution secondary electron microscopy (HR-SEM). This interdiffusion modifies the grain boundary phase and thus further enhances coercivity without decreasing remanence. The higher coercivity for DyCu compared to DyNiAl was attributed to the lower melting point obtained by differential scanning calorimetry (DSC). For NdCu and NdAl annealing was found to be ineffective. Following this, hot-compacted magnets have been die-upset in order to prepare textured composite magnets.
[1] Park et al. Proc. 16th Int. Workshop on RE Magnets and their Applications (Sendai, Japan) (2000) p.257