R-T-B Magnet Grain Boundary Dy Diffusion for Coercivity
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Solution Overview
Problem
Existing rare earth permanent magnets struggle to achieve high residual magnetic flux density and coercive force while maintaining corrosion resistance and production stability, particularly in achieving enhanced coercive force by diffusing heavy rare earth elements to grain boundaries.
Innovation Solution
An R-T-B based permanent magnet composition is developed, including specific elements such as Dy, Cu, Ga, Al, and Zr within precise content ranges, which enhances coercive force and residual magnetic flux density by diffusing heavy rare earth elements along grain boundaries, thereby improving magnetic properties and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If Dy content is increased to improve coercive force, then HcJ increases, but Br decreases and cost increases
Solution Approach 1:
The patent applies local quality by concentrating Dy at grain boundaries through diffusion treatment rather than uniform distribution. The grain boundary region receives higher Dy concentration (1.0-6.5 mass%) while the matrix maintains optimal composition, creating localized magnetic hardening at critical interfaces without bulk composition changes that would harm Br.
Solution Approach 2:
The patent segments the magnet structure into distinct regions: grain interiors maintaining high magnetization for Br, and grain boundaries enriched with Dy for coercivity enhancement. This segmentation allows independent optimization of each region's composition and properties.
2Force
If Dy content is increased to improve coercive force, then HcJ increases, but production cost increases
Solution Approach 1:
The patent uses partial action by applying Dy diffusion only to grain boundaries rather than throughout the entire magnet volume. This localized approach achieves the necessary coercivity enhancement with minimal Dy consumption, reducing material cost while maintaining performance.
Solution Approach 2:
The patent changes the spatial distribution parameter of Dy concentration, creating a gradient from low concentration in the matrix to high concentration at grain boundaries. This parameter optimization allows cost-effective achievement of target HcJ values.
3Force
If heavy rare earth element diffusion is enhanced to improve coercive force, then HcJ increases, but Br may decrease
Solution Approach 1:
By restricting heavy rare earth element enrichment to grain boundary regions through controlled diffusion, the patent preserves the high-magnetization matrix composition while achieving coercivity enhancement at interfaces, preventing Br degradation.
Solution Approach 2:
The patent performs preliminary optimization of base composition (R: 28.0-30.2 mass%, T: 65.0-70.0 mass%, B: 0.85-0.95 mass%) before diffusion treatment, ensuring the matrix has sufficient magnetization reserve to maintain Br after grain boundary modification.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The R-T-B magnet achieves superior magnetic properties, including high residual magnetic flux density and coercive force, while maintaining corrosion resistance and production stability, with the diffusion of heavy rare earth elements further enhancing coercive force without compromising other properties.
Implementation Method 1
a magnet body is immersed in a slurry dispersed with a fine powder including a rare earth element in water or organic solvent, then heated to diffuse the rare earth element into the magnet body along grain boundaries
Data Source
AI summary
An R-T-B based permanent magnet in which R is a rare earth element, T is Fe and Co, and B is boron. R at least includes Dy. The R-T-B based permanent magnet includes M, and M is at least one or more elements selected from the group consisting of Cu, Ga, Al, Mn, Zr, Ti, Cr, Ni, Nb, Ag, Hf, Ta, W, Si, Bi, and Sn. M at least includes Cu. A total content of R is 28.0 mass % to 30.2 mass %, a content of Dy is 1.0 mass % to 6.5 mass %, a content of Cu is 0.04 mass % to 0.50 mass %, a content of Co is 0.5 mass % to 3.0 mass %, and a content of B is 0.85 mass % to 0.95 mass %.