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

U.M.R. Seelam, T. Ohkubo, T. Abe, S. Hirosawa, K. Hono

doi:10.1016/j.jallcom.2014.07.166

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

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書誌事項

公開日: 2014-12

権利情報

https://www.elsevier.com/tdm/userlicense/1.0/
http://www.elsevier.com/open-access/userlicense/1.0/
https://doi.org/10.15223/policy-017
https://doi.org/10.15223/policy-037
https://doi.org/10.15223/policy-012
https://doi.org/10.15223/policy-029
https://doi.org/10.15223/policy-004

DOI

10.1016/j.jallcom.2014.07.166

公開者: Elsevier BV

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説明

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 °C. These microstructural features are explained on the basis of the phase equilibrium between Nd and Nd 2 Fe 14 B at the processing temperature and subsequent cooling. Based on the results, we discuss the coercivity enhancement by the GBDP using Dy vapor.