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Faceted shell structure in grain boundary diffusion-processed sintered Nd-Fe-B magnets

Journal of Alloys and Compounds

2014年5月26日(月)

Journal of Alloys and Compounds ( 617 (2014) 884–892 )
U.M.R.Seelam, T. Ohkubo, T. Abe, S. Hirosawa, K. Hono ( NIMS )

Abstract

Dysprosium enriched shell structure formed by the grain boundary diffusion process (GBDP) of a sintered Nd-Fe-B magnet was characterized by using scanning electron microscopy, electron back-scattered diffraction and transmission electron microscopy.
Faceted core-shell interfaces with an abrupt change in Dy concentration suggest the Dy-rich shells are formed by the solidification of the liquid phase during cooling from the GBDP temperature.
The Nd-rich phases are almost free from Dy, and their quantity near the surface of a bulk sample is much higher than that in the center, indicating that a higher fraction of a liquid phase exists near the surface during processing at 900 ℃.
These microstructural features are explained on the basis of the phase equilibrium between Nd and Nd2Fe14B at the processing temperature and subsequent cooling.
Based on the results, we discuss the coercivity enhancement by the GBDP using Dy vapor.

その他特記事項

This work is in part supported by Japan Science and Technology Agency, CREST, Japan. The samples for analysis were provided by Toyota Corporation, Japan.


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元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合