Nanocrystalline Rare Earth Magnet Composition for Higher Coercive Force
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Solution Overview
Problem
Current methods for improving the coercive force of anisotropic nanocrystalline rare earth permanent magnets are costly and inefficient, as they often require the addition of rare earth elements that increase material preparation costs and can react with other phases, limiting further improvements in magnetic properties.
Innovation Solution
The development of an anisotropic nanocrystalline rare earth permanent magnet with an RE-Fe-B matrix phase and a second phase comprising M-Cu or M-Cu-O phases, where M is Ca or Mg. This configuration allows for the reduction of rare earth oxides at the magnetic powder interface, improved distribution of the rare earth-rich phase, and refinement of main phase grains, thereby enhancing the coercive force of the magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rare earth elements are added in large amounts to improve coercive force, then the coercive force increases, but the material preparation cost increases
Solution Approach 1:
The invention changes the chemical composition parameters by introducing M-Cu-O phase (where M is Ca or Mg) instead of increasing rare earth content. This parameter substitution resolves the contradiction by achieving improved coercive force through a different compositional pathway that doesn't rely on increased rare earth quantities
Solution Approach 2:
The invention creates a composite microstructure consisting of RE2Fe14B main phase, RE-rich phase, and M-Cu-O secondary phase. This composite approach allows the M-Cu-O phase to perform the function of improving coercive force that would otherwise require additional rare earth elements, thereby resolving the cost-performance contradiction
2Strength
If RE-Cu phase is added at the grain boundary to improve coercive force, then the grain boundary phase is improved, but the material preparation cost increases due to increased rare earth usage
Solution Approach 1:
The invention replaces expensive rare earth-based RE-Cu phase with a cheaper alternative: M-Cu-O phase where M is Ca or Mg. These elements are more abundant and less costly than rare earth elements, while still achieving the desired grain boundary modification and coercive force improvement
Solution Approach 2:
The invention changes the grain boundary phase composition from RE-Cu to M-Cu-O, fundamentally altering the chemical parameters of the grain boundary phase. This substitution maintains the beneficial grain boundary effects while eliminating the need for additional rare earth elements
3Strength
If WC phase is added to improve coercive force through thermal deformation, then the coercive force is improved, but the WC phase reacts with Nd-rich phase and main phase RE2Fe14B, limiting further improvement of magnetic properties
Solution Approach 1:
The invention converts the potential harm of reactive grain boundary phases into a benefit by carefully selecting M-Cu-O phase that modifies the grain boundary without causing harmful reactions. The M-Cu-O phase creates a protective or beneficial interface that prevents unwanted reactions between the main phase and grain boundary phase, thus improving both coercive force and compositional stability
Solution Approach 2:
The M-Cu-O phase acts as an intermediary between the RE2Fe14B main phase and the RE-rich grain boundary phase. This intermediate phase prevents direct harmful interactions while facilitating the desired magnetic property improvements, resolving the contradiction between coercive force enhancement and compositional stability
4Strength
If high-melting rare earth oxides are used to optimize Nd-rich phase distribution, then part of the Nd-rich phase can diffuse into the magnetic powder, but the high-melting oxides cannot enter the magnetic powder, limiting further improvement of coercive force
Solution Approach 1:
The invention changes the melting temperature parameter of the grain boundary phase by using M-Cu-O phase with lower melting point characteristics compared to high-melting rare earth oxides. This temperature parameter change enables the grain boundary phase to be more effective at processing temperatures and allows better interaction with the magnetic powder, improving coercive force without the limitations of high-melting materials
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 cost-effectively improves the coercive force of anisotropic nanocrystalline rare earth permanent magnets by optimizing the microstructure and reducing the formation of coarse grains, making it suitable for industrial mass production.
Implementation Method 1
Ca and/or Mg in the M-Cu alloy could reduce the rare earth oxides at the RE-Fe—B magnetic powder interface
Data Source
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.