Rare Earth Magnet Phase Segregation for Coercive Force
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Solution Overview
Problem
In rare earth magnets, improving coercive force often leads to reduced magnetization due to the permeation of nonmagnetic modifiers between magnetic phases, which increases the content of nonmagnetic material.
Innovation Solution
A rare earth magnet composition with a main phase, grain boundary phase, and intermediate phase, where Ce and La concentrations are higher in the main phase than in the intermediate phase, and R2 concentrations are higher in the intermediate phase than in the main phase, with a specific atomic percentage range and heat treatment to prevent magnetization reduction while enhancing coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a nonmagnetic modifier is caused to permeate between magnetic phases to improve coercive force, then coercive force is improved, but magnetization is reduced due to increased nonmagnetic material content
Solution Approach 1:
The patent applies local quality by creating distinct phases with different compositions and functions: the main phase contains magnetic components for magnetization, the grain boundary phase contains the nonmagnetic modifier for magnetic separation, and the intermediate phase has specific composition to control the transition. This localized differentiation allows each phase to perform its specific function optimally without compromising the overall performance.
Solution Approach 2:
The patent employs composite materials by combining multiple phases with different magnetic properties: magnetic main phase, nonmagnetic grain boundary phase, and intermediate phase. This composite structure enables the material to simultaneously achieve high coercive force through magnetic separation and maintain high magnetization through the dominant magnetic phase, resolving the contradiction between these two properties.
2Force
If a modifier is provided between magnetic phases of a Nd-Fe-B rare earth magnet, then coercive force is improved by preventing magnetization reversal, but magnetization is generally reduced
Solution Approach 1:
The patent segments the magnet structure into three distinct phases: main phase, grain boundary phase, and intermediate phase. This segmentation allows the nonmagnetic modifier to be confined to the grain boundary phase where it performs magnetic separation, while the main phase maintains high magnetization. The intermediate phase acts as a transition zone, ensuring that the harmful effect of the nonmagnetic modifier is localized and does not propagate to reduce overall magnetization.
3Force
If Ce and La are replaced with R2 in the main phase to increase nonmagnetic material content, then coercive force is improved, but magnetization is reduced
Solution Approach 1:
The patent applies local quality by restricting the replacement of Ce and La with R2 to specific phases. The main phase retains Ce and La for high magnetization, while the grain boundary phase and intermediate phase contain higher R2 content for magnetic separation. This localized composition control allows the system to achieve improved coercive force without sacrificing the magnetization provided by Ce and La in the main phase.
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 solution effectively prevents magnetization reduction while improving coercive force by optimizing the distribution of rare earth elements and phases within the magnet, ensuring a balance between magnetic separation and overall magnetization.
Implementation Method 1
causing permeation of a modifier containing a Nd—Cu alloy, a Nd—Cu—Dy alloy, and/or a Nd—Cu—Tb alloy into a Nd—Fe—B rare earth magnet
Implementation Method 2
heating the contact body such that a liquid which is the melted modifier is permeated into the magnetic phase of the rare earth magnet precursor in a heat treatment
Implementation Method 3
when a nonmagnetic modifier permeates between magnetic phases, the magnetic phases can be magnetically separated from each other. As a result, since it is possible to prevent magnetization reversal proceeding across a plurality of magnetic phases, the coercive force is improved
Implementation Method 4
In a Nd—Fe—B rare earth sintered magnet, generally, anisotropy is imparted by strongly deforming a Nd—Fe—B rare earth magnet powder sintered material
Data Source
AI summary
A rare earth magnet includes a main phase, a grain boundary phase present around the main phase and an intermediate phase interposed between the main phase and the grain boundary phase, and has an overall composition that is represented by the formula ((Ce(1-x)Lax)(1-y)R1y)pT(100-p-q-r)BqM1r′(R21-zM2z)s (where, R1 and R2 are rare earth elements other than Ce and La, T is at least one selected from among Fe, Ni, and Co, M1 is an element having a small amount that does not influence magnetic characteristics, and M2 is an alloy element for which a melting point of R21-zM2z is lower than a melting point of R2). A total concentration of Ce and La is higher in the main phase than in the intermediate phase, and a concentration of R2 is higher in the intermediate phase than in the main phase.