NdFeB Magnet Composition for High Remanence and Coercivity
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Solution Overview
Problem
Current sintered neodymium-iron-boron magnets face challenges in achieving high remanence and coercivity while minimizing the use of heavy rare earth elements, leading to issues with demagnetization resistance and magnetic property stability, particularly in high-temperature applications and miniaturization of motors.
Innovation Solution
A neodymium-iron-boron magnet composition with specific weight percentages of rare earth elements, iron, boron, copper, gallium, and titanium, along with a controlled atomic ratio and a two-staged sintering process, to optimize grain boundary phases and main phase volume ratios, enhancing magnetic properties and coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If low-B component (0.80-0.93 wt %) is used to create R6T13M phase at grain boundary, then coercivity (Hcj) is improved, but remanence (Br) decreases due to reduced main phase volume proportion
Solution Approach 1:
The patent applies local quality by creating distinct phases with different compositions at different locations: the main phase contains high B content (2.00-2.30 wt %) for high remanence, while the grain boundary phase contains low B content (0.80-0.93 wt %) and R6T13M phase for high coercivity. This spatial differentiation of composition resolves the contradiction between remanence and coercivity.
Solution Approach 2:
The patent creates a composite microstructure consisting of main phase grains embedded in a grain boundary phase containing R6T13M phase. This composite structure allows the material to simultaneously exhibit high remanence from the main phase and high coercivity from the grain boundary phase, resolving the technical contradiction.
2Quantity of substance
If low-B component (0.94 wt %) is used with controlled columnar crystal proportion, then high remanence (1.44-1.48 T) and coercivity (14-16 kOe) are achieved, but grain boundary phase stability is poor and squareness fluctuates below 0.95
Solution Approach 1:
The patent changes the B content parameter to a higher range (2.00-2.30 wt %) in the main phase compared to prior art (0.94 wt %). This parameter change stabilizes the grain boundary phase composition, maintains squareness above 0.95, and ensures stable demagnetization resistance at high temperatures while still achieving high remanence and coercivity.
3Loss of substance
If heavy rare earth elements are reduced to lower cost, then cost is reduced, but demagnetization resistance at working temperatures deteriorates
Solution Approach 1:
The patent replaces expensive heavy rare earth elements (Dy, Tb, Ho) with cheaper light rare earth elements (Pr, La, Ce) in the grain boundary phase. This substitution reduces material cost while the R6T13M phase formation compensates for the lower intrinsic coercivity, maintaining adequate demagnetization resistance at working temperatures.
4Volume of moving object
If motor size is reduced for miniaturization, then energy density is improved, but magnetic property stability at high temperatures becomes difficult to maintain
Solution Approach 1:
The patent uses local quality by concentrating high B content (2.00-2.30 wt %) in the main phase grains to maximize remanence and energy density for miniaturization, while simultaneously concentrating light rare earth elements and R6T13M phase at the grain boundaries to maintain coercivity and magnetic stability at high temperatures, enabling both miniaturization and reliability.
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 proposed magnet achieves high remanence, coercivity, and squareness, ensuring stable magnetic performance and enabling the miniaturization of motors with improved energy efficiency and reduced material usage.
Implementation Method 1
a sintering process: subjecting the compacted powder to sintering to obtain a sintered magnet
Data Source
AI summary
A high-remanence neodymium-iron-boron magnet, and a preparation method and the use thereof are provided. The neodymium-iron-boron magnet has crystal grains with an R-T-B type compound as a main structure, and a grain boundary phase. By means of adjusting the proportional relation of elements such as B, Cu, Ga, RE and Ti, the neodymium-iron-boron magnet can achieve a relatively high main phase grain volume ratio and effectively restrain the proportion of a B-rich phase in the grain boundary phase, such that the magnet has relatively high Br, and also has both good Hcj and squareness performance.