R-T-B Sintered Magnet Grain Boundary Diffusion Coercivity

The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements within the magnet structure. Specifically, the grain boundary diffusion process concentrates heavy rare earth elements at the grain boundaries rather than uniformly throughout the entire magnet, achieving high coercivity at critical locations while minimizing overall material usage. The patent specifies that heavy rare earth element concentration at grain boundaries should be 1.0-5.0 times higher than in the crystal grain interior, which directly resolves the contradiction between improving coercivity and reducing material quantity.

The patent employs parameter changes by controlling the concentration ratio of heavy rare earth elements between grain boundaries and crystal grain interiors. By optimizing this concentration ratio parameter to be within 1.0-5.0 times, the patent achieves optimal coercivity while minimizing heavy rare earth element usage. Additionally, the patent controls the overall heavy rare earth element content to be 0.1-3.0 mass% of the total magnet weight, which further reduces material quantity while maintaining required magnetic performance.

The patent reduces manufacturing cost through local quality enhancement by concentrating heavy rare earth elements only where they are most effective - at the grain boundaries. This localized approach requires significantly less heavy rare earth material compared to uniform distribution, directly reducing material costs. The patent achieves coercivity of 1200 kA/m or higher with only 0.1-3.0 mass% heavy rare earth content, making the manufacturing process more cost-effective while maintaining high performance.

The patent optimizes manufacturing cost by controlling key parameters: the heavy rare earth element concentration ratio (1.0-5.0 times higher at grain boundaries) and the overall heavy rare earth content (0.1-3.0 mass%). These parameter optimizations minimize material consumption while achieving the required coercivity performance, thereby reducing overall manufacturing costs.

The patent simplifies the production process by applying local quality principles to the diffusion treatment. Instead of performing grain boundary diffusion on all six surfaces of the magnet, the patent selectively treats only the two main surfaces (larger area surfaces). This selective local treatment reduces the number of diffusion steps required while still achieving the desired coercivity enhancement, as the main surfaces provide sufficient diffusion pathways to achieve uniform grain boundary concentration throughout the magnet interior.

The patent inverts the conventional approach by treating fewer surfaces (two main surfaces) rather than all surfaces (six surfaces). This inversion simplifies the production process by reducing the number of diffusion steps from six to two, while the diffusion process itself ensures that heavy rare earth elements penetrate through the grain boundaries to achieve uniform distribution throughout the magnet interior, maintaining high coercivity performance.