[P1] RE-Fe-B Magnets

[P1-11] Regulation of Grain Boundary Structure in NdFeCoB Magnets through Grain Boundary Diffusion of DyAlCu Alloy

*Shengzhi Dong¹, Haibo Feng¹, Jing Liu¹, Jiateng Zhang¹, Wei Li¹ (1. Central lron & Steel Research Institute (China))

Keywords:

Grain Boundary Diffusion,NdFeCoB Magnet,Nd2Co17,Coercivity,Low-melting-point alloy

The optimization of grain boundary structure in sintered NdFeCoB magnets was studied using the grain boundary diffusion process (GBDP) with Dy₇₀Al₂₀Cu₁₀ alloy flakes as the diffusion source. These flakes were attached to magnets with a nominal composition of Pr_7.8Nd_23.4Co₁₂Fe_balAl_0.3Cu_0.2Zr_0.1B₁. Magnets with various coating thicknesses were labeled as follows: GBD-0 (0 mm), GBD-1 (0.03 mm), GBD-2 (0.09 mm), and GBD-3 (0.15 mm). Among them, GBD-3 exhibited optimal performance, increasing the coercivity from 7.94 to 17.63 kOe, which represented a significant enhancement of 122%. And the diffused magnet exhibited a more optimized temperature coefficient. Prior to GBDP, Co aggregated at grain boundaries with Nd₂Co₁₇ phase. After GBDP, microstructural analysis revealed the formation of Dy-rich shells with high anisotropy fields around the 2-14-1 phase within the magnet. Additionally, Al and Cu were uniformly distributed, which reduced Nd₂Co₁₇ content and enhanced coercivity. This study shows GBDP with " Heavy Rare Earth-Low Melting Point" alloys improves NdFeCoB magnets' magnetic properties, offering a theoretical basis for high-performance, temperature-stable sintered NdFeCoB magnets.

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