Low-temperature diffusion process for hot-deformed bulk permanent magnet using RE-Cu eutectic alloy

Takahiro Akiya, Keiko Hioki, Atsushi Hattori, H. Sepehri-Amin, Tadakatsu Ohkubo, Kazuhiro Hono

Research output: Contribution to journalArticlepeer-review


This paper reviews recent progresses in coercivity improvement of hot-deformed anisotropic Nd-Fe-B magnets by the low temperature grain boundary diffusion process using RE70Cu30 (RE = Pr, Nd) eutectic alloys. Using Pr70Cu30 alloy, the coercivity was enhanced from 1.60 T to 2.56 T. The hot-deformed samples are expanded along only c-axis direction after the diffusion process by the formation of thick Nd-rich grain boundary phase parallel to the c-planes of platelet shaped Nd2Fe14B grains. To suppress the reduction in remanence caused by the excess expansion during the diffusion process, we developed an expansion constraint eutectic diffusion process. We demonstrated high performance Dy-free anisotropy magnet with coercivity, μ0Hc = 1.94 T, and remanence, Br = 1.35 T, by the expansion constraint diffusion process using a Nd-Cu alloy as a diffusion source.

Original languageEnglish
Pages (from-to)478-483
Number of pages6
JournalIEEJ Transactions on Fundamentals and Materials
Issue number8
Publication statusPublished - 2016


  • Coercivity
  • Expansion constraint technique
  • Hot deformed Nd-Fe-B magnet
  • Low-temperature diffusion process


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