Loewe, K. ; Brombacher, C. ; Katter, M. ; Gutfleisch, O. (2015)
Temperature-dependent Dy diffusion processes in Nd–Fe–B permanent magnets.
In: Acta Materialia, 83
doi: 10.1016/j.actamat.2014.09.039
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
Nd–Fe–B permanent magnets have been coated with 0.6 wt.% dysprosium and annealed at various temperatures to study the impact of the temperature-dependent Dy diffusion processes on both the magnetic properties and the microstructure. When optimum annealing conditions are applied the Dy processed magnets with initial coercivity of ∼1100 kA m−1 yield coercivity increases which can exceed 400 kA m−1 without a significant reduction of the remanent magnetic polarization. The improved stability against opposing magnetic fields can be observed up to a depth of ∼3 mm along the diffusion direction, restricting the application of the Dy diffusion process to either thin magnets or magnets with tailored coercivity gradients. While in the proximity of the Dy-coated surface, each grain has a Dy-enriched shell with a Dy content of ∼6 at.%; the Dy concentration decreases exponentially to ∼1.8 at.% after a diffusion depth of 400 μm and to ∼1 at.% after a diffusion depth of 1500 μm, as was found with wavelength dispersive X-ray spectroscopy and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy, respectively. In the vicinity of the Dy-coated surface, the mechanism of the Dy-shell formation is attributed to the melting/solidification of a heavy-rare-earth-rich intermediate phase during high-temperature annealing. This is based on the observation that a constant Dy concentration over the width of the shells was found. Also an epitaxial relation between the Dy-poor core and the Dy-rich shell was observed by electron backscattered diffraction, which is supported by results obtained with Kerr microscopy.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2015 |
| Autor(en): | Loewe, K. ; Brombacher, C. ; Katter, M. ; Gutfleisch, O. |
| Art des Eintrags: | Bibliographie |
| Titel: | Temperature-dependent Dy diffusion processes in Nd–Fe–B permanent magnets |
| Sprache: | Englisch |
| Publikationsjahr: | 15 Januar 2015 |
| Verlag: | Elsevier Science Publishing |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Acta Materialia |
| Jahrgang/Volume einer Zeitschrift: | 83 |
| DOI: | 10.1016/j.actamat.2014.09.039 |
| Kurzbeschreibung (Abstract): | Nd–Fe–B permanent magnets have been coated with 0.6 wt.% dysprosium and annealed at various temperatures to study the impact of the temperature-dependent Dy diffusion processes on both the magnetic properties and the microstructure. When optimum annealing conditions are applied the Dy processed magnets with initial coercivity of ∼1100 kA m−1 yield coercivity increases which can exceed 400 kA m−1 without a significant reduction of the remanent magnetic polarization. The improved stability against opposing magnetic fields can be observed up to a depth of ∼3 mm along the diffusion direction, restricting the application of the Dy diffusion process to either thin magnets or magnets with tailored coercivity gradients. While in the proximity of the Dy-coated surface, each grain has a Dy-enriched shell with a Dy content of ∼6 at.%; the Dy concentration decreases exponentially to ∼1.8 at.% after a diffusion depth of 400 μm and to ∼1 at.% after a diffusion depth of 1500 μm, as was found with wavelength dispersive X-ray spectroscopy and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy, respectively. In the vicinity of the Dy-coated surface, the mechanism of the Dy-shell formation is attributed to the melting/solidification of a heavy-rare-earth-rich intermediate phase during high-temperature annealing. This is based on the observation that a constant Dy concentration over the width of the shells was found. Also an epitaxial relation between the Dy-poor core and the Dy-rich shell was observed by electron backscattered diffraction, which is supported by results obtained with Kerr microscopy. |
| Freie Schlagworte: | Nd–Fe–B, Permanent magnet, Coercivity enhancement, Grain boundary diffusion process, Microstructural characterization |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Funktionale Materialien |
| Hinterlegungsdatum: | 17 Nov 2014 09:55 |
| Letzte Änderung: | 18 Dez 2018 14:48 |
| PPN: | |
| Sponsoren: | Financial support from the Federal Ministry of Education and Research (BMBF) via the PerEMot project (No. 03X4621A) is gratefully acknowledged. |
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