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

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Abstract

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.

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Acknowledgements

This research was financially supported by the National Research Foundation of Korea (No. 2015R1A2A2A01 002795), the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Trade, Industry, and Energy, Republic of Korea (No. 10080382) and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2018R1D1A1B07041358).

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  1. Jeehye Kwon and Dajeong Lee contributed equally to this work.

Authors and Affiliations

  1. Department of Advanced Circuit Interconnection, Pusan National University, Busan, 46241, Republic of Korea

    Jeehye Kwon & Dongyun Lee

  2. Department of Nano Fusion Technology, Pusan National University, Busan, 46241, Republic of Korea

    Dajeong Lee, Dayoung Yoo, Seongkyu Park & Dongyun Lee

  3. Powder and Ceramics Department, Korea Institute of Machinery and Materials, Changwon, 51508, Republic of Korea

    Hee-Ryoung Cha & Junggoo Lee

  4. Department of Materials Science and Engineering, Pukyong National University, Busan, 48513, Republic of Korea

    Hae-Woong Kwon

  5. Department of Nanoenergy Engineering, Pusan National University, Busan, 46241, Republic of Korea

    Dongyun Lee

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  1. Jeehye Kwon
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Correspondence to Dongyun Lee.

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Kwon, J., Lee, D., Yoo, D. et al. Enhancement of magnetic properties of hot pressed/die-upset Dy-free Nd–Fe–B magnets with Cu/Nd coating by wet process. Rare Met. 39, 48–54 (2020). https://doi.org/10.1007/s12598-019-01277-4

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  • DOI: https://doi.org/10.1007/s12598-019-01277-4

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