Enhancement of magnetic properties of hot pressed/die-upset Dy-free Nd–Fe–B magnets with Cu/Nd coating by wet process

A grain boundary diffusion process (GBDP) was adopted to improve magnetic properties of Dy-free highly coercive Nd–Fe–B permanent magnet by coating thin layers of Nd and Cu in grain boundaries. For GBDP of Nd and Cu, Nd and Cu were coated by wet process, e.g., electrochemical and electroless on Nd–F...

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Bibliographic Details
Published in:Rare metals 2020-01, Vol.39 (1), p.48-54
Main Authors: Kwon, Jeehye, Lee, Dajeong, Yoo, Dayoung, Park, Seongkyu, Cha, Hee-Ryoung, Kwon, Hae-Woong, Lee, Junggoo, Lee, Dongyun
Format: Article
Language:English
Subjects:
Biomaterials
Boundaries
Chemistry and Materials Science
Coercivity
Cooling
Cooling rate
Deformation mechanisms
Diffusion coating
Energy
Grain boundaries
Grain boundary diffusion
Heat treating
Heat treatment
Magnetic properties
Magnetism
Materials Engineering
Materials Science
Melt spinning
Metallic Materials
Microstructure
Nanoscale Science and Technology
Neodymium
Permanent magnets
Physical Chemistry
Remanence
Thin films
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Summary:A grain boundary diffusion process (GBDP) was adopted to improve magnetic properties of Dy-free highly coercive Nd–Fe–B permanent magnet by coating thin layers of Nd and Cu in grain boundaries. For GBDP of Nd and Cu, Nd and Cu were coated by wet process, e.g., electrochemical and electroless on Nd–Fe–B magnets, which was fabricated by hot-deformed/die-upset with melt-spun specimen. Heat treatment was performed for 20 min at 600 °C followed by several different cooling conditions. The cooling conditions after heat treatment were varied to understand distribution and microstructural effects of Nd and Cu species in grain boundaries. The coercivity increased from 1.565 to 1.637 T in oil cooling rate but remanence decreased, while remanence jumped with little decrease in coercivity in furnace cooling. Microstructure analyses suggested that the coercivity was closely related to the cooling rate as well as distribution of Nd. The mechanism of coercivity enhancement due to the cooling rate was discussed based on the results presented here and those in the literature.
ISSN:1001-0521
1867-7185
DOI:10.1007/s12598-019-01277-4