Grain Boundary Dy Diffusion in R-Fe-B Sintered Magnets
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Solution Overview
Problem
Conventional methods for enhancing the coercivity of R-Fe-B based anisotropic sintered magnets using heavy rare-earth elements like Dy face challenges such as diffusion issues during sintering, wastage of rare resources, and inefficient distribution, leading to decreased remanence and coercivity.
Innovation Solution
A method where a portion of the light rare-earth element is replaced with a heavy rare-earth element, specifically Dy, in the R-Fe-B based anisotropic sintered magnet, with a controlled diffusion process that preferentially advances grain boundary diffusion over intragrain diffusion, creating a high concentration layer of Dy in the outer periphery of the main phase grains, thereby increasing coercivity without significantly reducing remanence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare-earth element RH is added to replace light rare-earth element RL in the entire magnet, then coercivity is improved, but remanence decreases and rare resource consumption increases
Solution Approach 1:
The patent applies local quality by concentrating the heavy rare-earth element RH specifically in the grain boundary phases rather than uniformly distributing it throughout the entire magnet. This localized approach allows the grain boundaries to have high RH concentration for improved coercivity, while the main phase retains light rare-earth element RL for maintaining remanence, thus resolving the contradiction between improving coercivity and preserving remanence
2Force
If heavy rare-earth element RH is added to replace light rare-earth element RL in the entire magnet, then coercivity is improved, but rare resource consumption increases
Solution Approach 1:
The patent concentrates RH in the grain boundary phases where it is most effective for improving coercivity, rather than distributing it uniformly throughout the entire magnet. This localized distribution reduces the total amount of heavy rare-earth element RH needed, thereby reducing rare resource consumption while still achieving the desired coercivity improvement
3Force
If heavy rare-earth element RH is distributed only in the outer periphery of the main phase grain, then magnetocrystalline anisotropy is improved and coercivity increases, but RH diffusion during sintering becomes difficult to control
Solution Approach 1:
The patent uses preliminary action by pre-distributing the heavy rare-earth element RH in the grain boundary phases before the sintering process. This pre-positioning ensures that during sintering, RH remains concentrated at the grain boundaries rather than diffusing into the main phase, making the diffusion process easier to control and achieving the desired coercivity improvement without excessive RH consumption
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 increases coercivity while minimizing the decrease in remanence and reduces the amount of heavy rare-earth element required, achieving enhanced magnetic properties with efficient resource utilization.
Implementation Method 1
a controlled diffusion process that preferentially advances grain boundary diffusion over intragrain diffusion, creating a high concentration layer of Dy in the outer periphery of the main phase grains
Implementation Method 2
R-Fe-B based anisotropic sintered magnet
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 4(a)~4(b)
AI summary
An R-Fe-B based anisotropic sintered magnet according to the present invention has, as a main phase, an R2Fe14B type compound that includes a light rare-earth element RL (which is at least one of Nd and Pr) as a major rare-earth element R, and also has a heavy rare-earth element RH (which is at least one element selected from the group consisting of Dy and Tb). In the crystal lattice of the main phase, the c-axis is oriented in a predetermined direction. The magnet includes a portion in which at least two peaks of diffraction are observed within a 2θ range of 60.5 degrees to 61.5 degrees when an X-ray diffraction measurement is carried out using a CuK α ray on a plane that is located at a depth of 500 µm or less under a pole face of the magnet and that is parallel to the pole face.