Rare-Earth Magnet Grain Size Control via Surface Diffusion
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Solution Overview
Problem
Conventional Nd—Fe—B based rare-earth magnets face limitations in reducing grain size and improving coercive force, which affects their magnetic properties.
Innovation Solution
A rare-earth magnet with a specific composition of (R1(1-x)R2x)yFe(100-y-z-v-w)CozBvTMlw, where R1 includes Nd or Pr, R2 includes Ce, and a diffusion metal of (LRE(100-p-q)HREp)TM2q is diffused on the surface of a hot deformed magnet precursor, optimizing the coercive force and residual magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Nd-Fe-B based sintered rare-earth magnet is used, then manufacturing process is simple, but grain size cannot be reduced and coercive force cannot be improved
Solution Approach 1:
The patent applies preliminary action by pre-forming the magnet precursor with controlled grain size through hot pressing before the diffusion process. The precursor is prepared with specific grain size (5-20 μm) and then subjected to diffusion treatment to achieve the desired magnetic properties without requiring complex post-processing steps.
Solution Approach 2:
The patent uses composite materials by combining the rare-earth magnet precursor with a diffusion metal layer containing heavy rare-earth elements (Dy, Th) and transition metals (Ti, Ga, Zn, Si, Al, Nb, Zr, Mn, V, W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Ag, or Au). This composite structure allows grain size control in the precursor while adding coercive force enhancement through the diffusion layer.
2Force
If diffusion metal is added to improve coercive force, then coercive force increases, but residual magnetization decreases
Solution Approach 1:
The patent applies local quality by concentrating the heavy rare-earth elements (Dy, Th) and transition metals specifically in the diffusion layer on the surface and near-surface regions of the magnet precursor. The diffusion metal content is controlled to be 6 to 12 parts by weight based on 100 parts by weight of the rare-earth magnet precursor, creating a gradient distribution that enhances coercive force locally without uniformly reducing residual magnetization throughout the entire magnet.
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
This approach effectively enhances coercive force while minimizing the reduction in residual magnetization, thereby improving the overall magnetic properties of the rare-earth magnet.
Implementation Method 1
a diffusion metal including a composition of (LRE(100-p- q)HREp)TM2q, and diffused on the surface of the rare-earth magnet precursor
Data Source
AI summary
A rare-earth magnet according to an embodiment of the present invention comprises: a rare-earth magnet precursor including a composition of (R1(1-x)R2x)yFe(100-y-z-v-w)CozBvTMlw in which R1 comprises at least one of Nd or Pr, and R2 comprises Ce; and a diffusion metal including a composition of (LRE(100-p-q)HREp)TM2q, and diffused on the surface of the rare-earth magnet precursor, wherein the LRE in the diffusion metal can comprise light rare earth including Y, and the HRE can comprise heavy rare earth.