Sm-Co Magnet Phase Separation for Coercive Force
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Solution Overview
Problem
Sm—Co based permanent magnets with high Fe concentration face challenges in achieving both high coercive force and magnetic flux density due to the decrease in coercive force with increased Fe concentration, which is exacerbated by insufficient Cu concentration in the main phase, leading to inadequate phase separation and magnetic domain wall pinning.
Innovation Solution
A permanent magnet composition with an Fe concentration of 28 mol % or more and a Cu concentration of 5 mol % or more in the main phase, achieved by controlling the sintering temperature to suppress the generation of Cu-M rich phases, ensuring sufficient phase separation and magnetic domain wall pinning, thereby enhancing coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Fe concentration in Sm—Co based magnets is increased to achieve high magnetic flux density, then magnetic flux density is improved, but coercive force decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Fe concentration within 28-40 atomic % and Cu concentration within 4-13.5 atomic % ranges. By optimizing these compositional parameters, the patent achieves a balance where high magnetic flux density is maintained while coercive force is preserved through the specific interaction between Fe and Cu atoms in the crystal structure.
Solution Approach 2:
The patent creates a composite material system by combining Sm, Co, Fe, and Cu elements in specific proportions to form a multi-phase structure. The main phase contains high Fe concentration for magnetic flux density, while Cu-rich secondary phases form at grain boundaries to provide pinning sites for domain walls, thus maintaining coercive force despite high Fe content.
2Ease of manufacture
If Cu concentration in main phase is insufficient, then manufacturing is simplified, but phase separation and magnetic domain wall pinning become inadequate, reducing coercive force
Solution Approach 1:
The patent applies parameter changes by setting the Cu concentration in the main phase to 5 mol % or more, which is sufficient to enable effective phase separation and magnetic domain wall pinning. This parameter optimization ensures that Cu atoms are distributed appropriately during sintering to form the necessary microstructure for high coercive force without requiring overly complex manufacturing processes.
3Temperature
If Dy is used to increase heat resistance in Nd—Fe—B based magnets, then heat resistance is improved, but cost increases due to Dy being a rare element
Solution Approach 1:
The patent replaces expensive rare earth elements like Dy with more abundant elements (Sm, Co, Fe, Cu) that can achieve similar or superior performance. By using Sm—Co based magnets with optimized Fe and Cu concentrations, the patent achieves high heat resistance and magnetic performance without relying on scarce and expensive Dy, thus reducing material costs while maintaining functional performance.
Solution Approach 2:
The patent applies parameter changes by adjusting the compositional ratios of Sm, Co, Fe, and Cu to achieve high Curie temperature and heat resistance inherent to the Sm—Co system. The specific composition ranges ensure that the magnet maintains stable magnetic properties at elevated temperatures without requiring additional rare earth elements for thermal stabilization.
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 approach results in a Sm—Co based magnet with improved coercive force and magnetic characteristics, maintaining high Cu concentration in the main phase and optimizing the phase separation, leading to enhanced magnetic performance.
Implementation Method 1
a composition region having an Fe concentration of 28 mol % or more is a main phase. A Cu concentration in the main phase is set to 5 mol % or more
Implementation Method 2
achieved by controlling the sintering temperature to suppress the generation of Cu-M rich phases
Data Source
AI summary
In one embodiment, a permanent magnet includes a composition represented by RpFeqMrCusCo100-p-q-r-s (R: rare earth element, M: at least one element selected from Zr, Ti and Hf, 10≦p≦13.5 atomic %, 28≦q≦40 atomic %, 0.88≦r≦7.2 atomic %, 4≦s≦13.5 atomic %), and a metallic structure in which a composition region having an Fe concentration of 28 mol % or more is a main phase. A Cu concentration in the main phase is 5 mol % or more.