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Super-High Coercivity Sintered NdFeB Magnets Enabled by High-Rate Dy/Tb Grain Boundary Synergistic Diffusion
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DOI：10.1002/rar2.70238.png)
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Abstract
En 中文
The surging demand for high-performance NdFeB magnets has made it essential to achieve ultrahigh coercivity while minimizing the consumption of heavy rare earths. To tackle this challenge, this study proposes a Dy/Tb bilayer grain boundary diffusion strategy and systematically investigates the co-diffusion behavior of Dy and Tb. Benefiting from Dy/Tb co-diffusion, the diffused magnet (N50/Dy3μm/Tb11μm, using 3 μm Dy and 11 μm Tb as diffusion sources) achieves a super-high coercivity of 22.66 kOe representing a 10.10 kOe increase over the pristine N50 magnet (12.56 kOe). Notably, the remanence and maximum magnetic energy product remain largely preserved (Br = 14.21 kGs (BH)max = 50.47 MGOe), showing only marginal reductions (1.73% and 1.45%, respectively), approaching the performance of commercial G52 SHB super-high coercivity NdFeB magnets. This coercivity enhancement is primarily attributed to the markedly increased grain boundary diffusion coefficients of Dy and Tb. Specifically, the Dy diffusion rate increases from (6.68 ± 0.41) × 10−8 to (1.28 ± 0.32) × 10−6 mm2 s−1, whereas the Tb diffusion rate rises from (2.73 ± 0.34) × 10−7 to (7.31 ± 1.34) × 10−7 mm2 s−1. The accelerated HRE transport promotes the formation of continuous (Nd,Dy,Tb)2Fe14B core–shell structures, and their widespread distribution throughout the magnet is identified as the key microstructural origin of the enhanced coercivity. These findings offer clear guidance for the design of diffusion sources in next-generation high-performance sintered NdFeB magnets.
Keywords:
coercivity
grain boundary diffusion coefficient
heavy rare earth
sintered NdFeB magnets
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