Anisotropic RE-Fe-B Nanocrystalline Magnet With M-Cu Grain Boundaries
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Solution Overview
Problem
Existing methods for improving the coercive force of anisotropic nanocrystalline rare earth permanent magnets are costly and limited by the reaction of high-melting phases with the main phase, leading to reduced magnetic properties and increased material costs.
Innovation Solution
Incorporating a low-melting M-Cu alloy, where M is Ca or Mg, into the RE-Fe-B matrix phase to form an M-Cu phase or M-Cu-O phase at the grain boundary, which inhibits grain growth and oxidizes rare earth oxides, thereby enhancing the coercive force without additional rare earth elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-melting RE-Cu phase is added at the grain boundary to improve coercivity, then coercive force is improved, but material preparation cost increases due to large amount of RE elements
Solution Approach 1:
The invention changes the melting point parameter of the grain boundary phase by using high-melting WC phase instead of low-melting RE-Cu phase. This allows the grain boundary phase to have different thermal characteristics that prevent RE element consumption while still improving coercivity through grain boundary isolation and refinement effects.
Solution Approach 2:
The invention replaces expensive rare earth elements with cheaper WC (tungsten carbide) phase for grain boundary modification. WC serves as a cost-effective alternative that achieves the same grain boundary isolation function without the high material cost associated with large amounts of RE elements.
2Reliability
If high-melting WC phase is added to improve coercive force through thermal deformation, then coercive force is improved, but WC phase reacts with Nd-rich phase and main phase RE2Fe14B, limiting further improvement of magnetic properties
Solution Approach 1:
The invention introduces M-Cu alloy powder as an intermediary substance that mediates between the WC phase and the magnetic phases. The M-Cu alloy forms a protective barrier or intermediate layer that prevents direct chemical reactions between WC and the Nd-rich phase or RE2Fe14B main phase, thereby maintaining chemical stability while preserving the coercivity enhancement benefits.
3Reliability
If appropriate heat treatment is applied to optimize Nd-rich phase distribution, then coercive force is improved, but large number of rare earth oxides remain at magnetic powder interface, limiting further improvement
Solution Approach 1:
The invention extracts and removes rare earth oxides from the magnetic powder interface through the action of M-Cu alloy powder. The M-Cu alloy reacts with or facilitates the removal of these oxide inclusions, thereby purifying the interface region and enabling further improvement of coercive force that was previously limited by the presence of these oxides.
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 improves the coercive force of anisotropic nanocrystalline rare earth permanent magnets by refining grain structure and reducing rare earth oxides, resulting in a cost-effective and efficient magnet with optimized microstructure.
Implementation Method 1
Incorporating a low-melting M-Cu alloy, where M is Ca or Mg, into the RE-Fe-B matrix phase to form an M-Cu phase or M-Cu-O phase at the grain boundary
Implementation Method 2
which inhibits grain growth and oxidizes rare earth oxides, thereby enhancing the coercive force
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Disclosed are an anisotropic nanocrystalline rare earth permanent magnet and a preparation method thereof. The rare earth permanent magnet includes an RE-Fe-B matrix phase and a second phase, wherein the RE-Fe-B matrix phase includes main phase RE2Fe14B flaky nanocrystallines regularly arranged and an RE-rich phase around main phase grains, the main phase RE2Fe14B flaky nanocrystallines having an average grain size in a length direction of 70 nm to 800 nm and an average grain size in a thickness direction of 30 nm to 200 nm; and the second phase includes at least one selected from the group consisting of an M-Cu phase and an M-Cu-O phase, M being at least one selected from the group consisting of Ca and Mg. Ca and/or Mg in an M-Cu alloy could reduce rare earth oxides at an interface of RE-Fe-B magnetic powder, thereby improving the rare earth-rich phase distribution and refining grains of main phase nanocrystallines. In addition, the second phase distributed at the interface of magnetic powder inhibits formation of coarse grains at the interface of the magnetic powder, optimizes a microstructure of magnet, and improves coercive force thereof.