Nd-Ce-Fe-B Magnet Microstructure for High Coercivity Diffusion
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Solution Overview
Problem
The formation of CeFe2 phases and uneven distribution of RE-rich phases in neodymium-cerium-iron-boron magnets hinder high coercivity and residual magnetic flux density, necessitating a solution to inhibit CeFe2 phases and optimize RE-rich phase distribution.
Innovation Solution
A method involving powder preparation, pressing, sintering, and aging treatment is employed, with controlled grain boundary RE-rich phase distribution and sintering schemes to achieve uniform, fine distribution of RE-rich phases, inhibiting anti-magnetization domain nucleation and enhancing magnetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sintering methods are used to improve productivity, then manufacturing efficiency increases, but manufacturing precision deteriorates due to grain growth and oxidation
Solution Approach 1:
The invention changes the sintering parameters by conducting sintering in a vacuum environment (vacuum degree 10^-2 to 10^-4 Pa) and controlling temperature (1020-1120°C) and time (5-15 minutes) to prevent oxidation and grain growth while maintaining high productivity. This resolves the contradiction by optimizing multiple parameters simultaneously rather than using conventional atmospheric sintering.
Solution Approach 2:
The invention uses vacuum as an inert environment during sintering to prevent oxidation of the Nd-Fe-B powder and alloying elements. The vacuum sintering process creates an oxygen-free atmosphere that protects the magnetic powder from oxidation while enabling efficient manufacturing, thus improving both productivity and manufacturing precision.
2Quantity of substance
If high-temperature sintering is used to improve density, then relative density increases, but manufacturing precision deteriorates due to grain growth and phase segregation
Solution Approach 1:
The invention optimizes the combination of sintering temperature (1020-1120°C), time (5-15 minutes), and vacuum degree (10^-2 to 10^-4 Pa) to achieve high relative density (≥95%) while preventing grain growth and phase segregation. The controlled parameters ensure dense microstructure with uniform grain distribution and proper phase composition.
Solution Approach 2:
The invention performs preliminary alloying by adding rare earth elements (Ce, La, Pr) and other elements (Al, Si, B, Cu, Mo, W) to the Nd-Fe-B powder before sintering. This preliminary composition adjustment ensures that during vacuum sintering, the material achieves high density without excessive grain growth, as the alloying elements control grain boundary behavior and phase formation during the sintering process.
3Reliability
If conventional alloying methods are used to improve coercivity, then magnetic performance improves, but manufacturing precision deteriorates due to composition control difficulties
Solution Approach 1:
The invention changes the alloying strategy by adding specific amounts of Ce (0.1-5 wt%), La (0.1-5 wt%), Pr (0.1-5 wt%), and other elements (Al: 0.1-5 wt%, Si: 0.1-5 wt%, B: 0.01-1 wt%, Cu: 0.1-5 wt%, Mo: 0.01-1 wt%, W: 0.01-1 wt%) to the Nd-Fe-B powder. These compositional changes enhance coercivity through grain boundary phase formation and magnetic anisotropy improvement while maintaining precise composition control through the vacuum sintering process.
Solution Approach 2:
The invention creates a composite microstructure by combining Nd-Fe-B magnetic powder with alloying elements that form grain boundary phases during vacuum sintering. The composite structure consists of magnetic grains separated by alloy-rich grain boundary phases containing Ce, La, Pr, Al, Si, and other elements, which provide both high coercivity and precise composition control through the vacuum processing method.
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 results in high-coercivity neodymium-cerium-iron-boron magnets with improved magnetic performance and uniform RE-rich phase distribution, inhibiting anti-magnetization domain nucleation and enhancing magnetic exchange coupling.
Implementation Method 1
the crystal structure is one of (Nd, Ce, La, Pr)2Fe14B type, and the easy magnetization direction is along the c-axis direction, so that the magnet has high coercivity
Implementation Method 2
High-coercivity neodymium-cerium-iron-boron permanent magnet
Implementation Method 3
vacuum sintering
Data Source
Figure 1~2
Figure 3
AI summary
Disclosed are a high-coercivity neodymium-cerium-iron-boron permanent magnet as well as a preparation method therefor and the use thereof. The permanent magnet has at least one of the following features: the area of grain boundary RE-rich phases in the magnet accounts for 4% or more of the area of a whole field of view; the grain boundary RE-rich phases in the magnet are fine and uniformly distributed; and the mean value of ratios of the area of block-shaped grain boundary RE-rich phases located at intersections of three or more main-phase grains to the total area of all the three or more adjacent main-phase grains in the vicinity is less than or equal to 30%. When used as a grain boundary diffusion magnet base material, the magnet prepared in the present invention has an excellent diffusion effect. As the RE-rich phases in the magnet are continuously distributed along grain boundaries, more channels are provided for diffusion, thereby helping to increase the depth of diffusion of a diffusion source into the magnet, improve the uniformity of distribution of the diffusion source in the magnet and improve the consistency of internal structure components of the diffusion magnet, and thus further improving the magnetic performance of the diffusion magnet.