NdFeB Magnet Composition for High-Temperature Coercive Force
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Solution Overview
Problem
Existing neodymium-iron-boron rare earth permanent magnets suffer from low Co addition, low Curie temperature, insignificant improvement in remanence temperature coefficient, and low coercive force, limiting their application in high-temperature environments and mechanical reliability.
Innovation Solution
A neodymium-iron-boron rare earth permanent magnet composition with high Co content, specific microstructure comprising R2(Fe, Co)14B as the main phase, R(Fe, Co)2 as the grain boundary phase A, and R4(Fe, Co)3 as the grain boundary phase B, along with controlled amounts of Pr, Al, and other elements, to enhance coercive force and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Co is added to improve Curie temperature and temperature coefficient, then temperature stability is improved, but coercive force deteriorates due to soft magnetic phase precipitation
Solution Approach 1:
The patent introduces Al as an intermediary element that mediates between Co and the rare earth matrix. Al forms a protective interface layer that prevents Co from precipitating as soft magnetic phase, thereby maintaining both high Curie temperature and high coercive force simultaneously
Solution Approach 2:
The patent creates a composite microstructure consisting of R2(Fe, Co)14B main phase, R(Fe, Co)2 grain boundary phase, and R4(Fe, Co)3 grain boundary phase. This composite structure allows Co to be distributed in multiple phases, preventing soft magnetic phase precipitation while maintaining temperature stability and coercive force
2Reliability
If heavy rare earth elements are added to improve coercive force, then coercive force is improved, but manufacturing complexity increases due to rapid cooling requirements
Solution Approach 1:
Al acts as a mediator that eliminates the need for rapid cooling by preventing soft magnetic phase precipitation during normal cooling rates. This simplifies the manufacturing process while maintaining high coercive force through optimized phase distribution
Solution Approach 2:
The patent changes the compositional parameters by adding Al and optimizing the ratio of rare earth elements, which transforms the phase transformation characteristics during cooling. This allows standard cooling rates to produce the desired microstructure without complex rapid cooling equipment
3Temperature
If Co addition is increased to improve temperature coefficient, then temperature stability is improved, but remanence deteriorates due to low Co addition in existing technologies
Solution Approach 1:
The patent creates a composite microstructure with Co distributed across three phases (R2(Fe, Co)14B main phase, R(Fe, Co)2 grain boundary phase, and R4(Fe, Co)3 grain boundary phase). This composite structure allows high total Co content (12-20 wt%) while maintaining high remanence through optimized phase distribution and preventing soft magnetic phase precipitation
Data Source
AI summary
The invention discloses a neodymium-iron-boron rare earth permanent magnet, a preparation method and use thereof. The neodymium-iron-boron rare earth permanent magnet comprises: R: 28.5-33 wt %, wherein RL comprises Pr, Pr≥14 wt %, and RH comprises one or more of Dy, Tb, Gd and Ho; Co: 12-20 wt %; Al: 0.5-1.5 wt %; X: 0.3-1.5 wt %; B: 0.88-1.05 wt %; and a balance of Fe, the microstructure thereof comprises a main phase M, a grain boundary phase A and a grain boundary phase B; the main phase M is R2(Fe, Co)14B having a volume percentage of 90-94%; the grain boundary phase A is R(Fe, Co)2 having a volume percentage of 5-8%; and the grain boundary phase B is R4(Fe, Co)3 having a volume percentage of 1-2%. The neodymium-iron-boron rare earth permanent magnet has a high Co content, a high Curie temperature, a low temperature coefficient, good mechanical properties, a high magnetic energy product and a high coercive force.