Sintered R-Fe-B Magnet Core-Shell Structure for High Coercivity
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Solution Overview
Problem
Existing methods for incorporating La and Ce into sintered neodymium-iron-boron magnets often reduce the magnetic properties of the main phase grains and are costly due to inefficient diffusion and low coercivity.
Innovation Solution
A sintered R-Fe-B permanent magnet with a core-shell structure and grain boundary diffusion, where the grain boundary contains an RH-rich phase and the composite main phase grains have a Ce-rich and Ce-poor core structure, with RL-enriched shells and RH-enriched grain boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If La and Ce are added by alloying during smelting, then the cost is reduced by increasing usage of abundant rare earth elements, but the magnetic properties of main phase grains (saturation magnetic polarization intensity, Curie temperature, magnetocrystalline anisotropy field) are reduced
Solution Approach 1:
The patent divides the magnet structure into distinct regions: main phase grains (preserving high magnetic properties) and grain boundary phases (enriched with La and Ce). This segmentation allows La and Ce to be concentrated in grain boundary phases rather than uniformly distributed, preventing degradation of main phase magnetic properties while achieving cost reduction through increased usage of abundant rare earth elements.
Solution Approach 2:
The patent creates local quality differences by forming La and Ce enriched grain boundary phases with specific structures (e.g., R2Fe14B grain boundary phase with La and Ce enrichment). This local concentration of La and Ce in grain boundary regions allows cost reduction without affecting the overall magnetic properties of the main phase grains.
2Reliability
If La and Ce are added by diffusion heat treatment, then the main phase properties are preserved, but the process becomes complicated and the addition amount is insufficient
Solution Approach 1:
The patent prepares (R, LaCe)-Fe-B alloy slices with predetermined La and Ce content before sintering. This preliminary incorporation of La and Ce into the alloy structure eliminates the need for subsequent diffusion heat treatment processes, simplifying the overall manufacturing process while ensuring sufficient La and Ce addition amounts are achieved from the beginning.
Solution Approach 2:
The patent extracts the complex diffusion heat treatment step from the preparation process by directly incorporating La and Ce into the alloy slices during smelting. This removes the complicated multi-step diffusion process while achieving the same or better effect of La and Ce incorporation.
3Reliability
If heavy rare earth elements (Dy, Tb) are added to improve coercivity, then the magnetic properties are enhanced, but the cost increases and the process becomes more complex
Solution Approach 1:
The patent uses abundant and cheaper La and Ce elements to achieve the grain boundary diffusion effect that was previously requiring expensive heavy rare earth elements. By forming La and Ce enriched grain boundary phases, the patent achieves comparable or superior coercivity enhancement at lower cost, effectively replacing expensive Dy and Tb with more economical rare earth elements.
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 significantly improves the coercivity and squareness of the permanent magnet, enhancing its resistance to demagnetization at high temperatures and achieving a high coercivity magnetic property.
Implementation Method 1
perform an appropriate heat treatment process to diffuse La and Ce into the interior of the magnet
Implementation Method 2
sinter the alloy slices described above after mixing them in a certain ratio
Data Source
Figure 1~2
Figure 3a~5b
AI summary
The present disclosure provides a sintered R-Fe-B permanent magnet, a preparation method and use thereof. The permanent magnet comprises at least a grain boundary and composite main phase grains, wherein the grain boundary comprises an RH-rich phase distributed in the form of an agglomerate within the grain boundary between the composite main phase grains, preferably at the intersection of any adjacent three or more composite main phase grains, and the RH-rich phase is continuously distributed along the grain boundary in the form of a thin-layer stripe; the composite main phase grain has a core-shell structure, wherein the core-shell structure comprises a core structure having an R-T-B type phase structure and a shell structure on the outer layer of the core structure; the core structure comprises Ce-rich main phase grains and Ce-poor main phase grains. The permanent magnet prepared by the present disclosure has a high coercivity magnetic property and squareness, and the capacity of resisting demagnetization of the magnet at a high temperature is significantly improved.