Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process

Lihua Liu, H. Sepehri-Amin, T. Ohkubo, M. Yano, A. Kato, T. Shoji, K. Hono

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd90Al10 exhibited the highest coercivity of 2.5 T at room temperature. However, the sample processed with Nd70Cu30 exhibited the highest coercivity of 0.7 T at 200 °C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd2Fe14B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd2Fe14B grains were observed in the sample processed with Nd90Al10, which explains its inferior thermal stability of coercivity compared to the sample processed with Nd70Cu30. The coercivity enhancement and poor thermal stability of the coercivity of the Nd90Al10 diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy.

Original languageEnglish
Pages (from-to)432-439
Number of pages8
JournalJournal of Alloys and Compounds
Volume666
DOIs
Publication statusPublished - 2016 May 5
Externally publishedYes

Keywords

  • Coercivity
  • Diffusion process
  • Grain boundary phase
  • Nd-Fe-B
  • Permanent magnets

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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