Rare Earth Sintered Magnet Diffusion for Coercivity Without Remanence Loss
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Solution Overview
Problem
Existing methods for manufacturing rare earth sintered magnets face challenges in achieving high remanence and coercivity while maintaining productivity, as grain boundary diffusion techniques can lead to a decline in remanence and require discrete treatment of magnets, reducing throughput.
Innovation Solution
A method involving the use of an alloy powder containing Dy or Tb, along with boron, is applied to the surface of a rare earth sintered body, where heat treatment enhances coercivity without significantly reducing remanence, and allows for multiple magnets to be treated in contact without fusion, thereby increasing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy or Tb is added to increase coercivity through substitution, then coercivity is improved, but remanence decreases due to substitution in grain interior
Solution Approach 1:
The patent applies local quality by concentrating Dy or Tb substitution specifically at grain boundaries rather than uniformly throughout the grain interior. The diffusion treatment creates a concentration gradient where rare earth elements are enriched at grain boundaries (forming R2Fe14B phase with high Dy/Tb content) while maintaining lower concentrations in the grain interior, thus improving coercivity through boundary effects while preserving remanence through intact interior regions.
2Strength
If grain boundary diffusion technology is used to increase coercivity, then coercivity is improved, but productivity decreases due to requirement for discrete magnet treatment
Solution Approach 1:
The patent merges multiple magnets into a stacked configuration during the diffusion treatment process. Multiple magnet pieces are stacked in contact with each other and treated simultaneously in a single diffusion process, allowing concurrent modification of all magnets in the stack. This eliminates the need for discrete individual treatment and significantly improves productivity while maintaining the grain boundary diffusion mechanism for coercivity enhancement.
3Strength
If diffusion source is disposed on magnet surface for grain boundary diffusion, then coercivity is improved, but remanence decreases due to diffusion into R2Fe14B major phase
Solution Approach 1:
The patent applies partial action by controlling the diffusion process to achieve sufficient Dy/Tb concentration at grain boundaries without excessive diffusion into the grain interior. The diffusion treatment parameters (temperature, time, source composition) are optimized to create adequate enrichment at boundaries for coercivity improvement while limiting penetration depth to prevent significant remanence loss. The alloy powder composition and heat treatment conditions are tuned to achieve the desired concentration gradient.
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 method effectively increases coercivity while minimizing the decline in remanence, enabling the production of rare earth sintered magnets with high remanence and coercivity at higher productivity levels.
Implementation Method 1
the diffusion source, infiltrates and diffuses along liquid grain boundaries in the magnet
Implementation Method 2
During the heat treatment, the diffusion source melts by itself or melts as a result of reaction with molten magnet grain boundary phase components
Data Source
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AI summary
A rare earth sintered magnet is manufactured by preparing a R1-T-X sintered body having a major phase of R12T14X composition wherein R1 is a rare earth element(s) and essentially contains Pr and/or Nd, T is Fe, Co, Al, Ga, and/or Cu, and essentially contains Fe, and X is boron and/or carbon, forming an alloy powder containing 5 ≤ R2 ≤ 60, 5 ≤ M ≤ 70, and 20 < B ≤ 70, in at%, wherein R2 is a rare earth element(s) and essentially contains Dy and/or Tb, M is Fe, Cu, Al, Co, Mn, Ni, Sn, and/or Si, and B is boron, disposing the alloy powder on the sintered body, and heat treating the alloy-covered sintered body.