NdFeB Magnet Grain Boundary Composition for Thermal Stability
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Solution Overview
Problem
Existing methods for enhancing the temperature stability of NdFeB magnets, such as adding heavy rare earth elements or using different production processes, are costly and result in uneven grain boundary phases leading to reduced magnet performance and stability.
Innovation Solution
A high-performance NdFeB magnet with a specific composition and manufacturing process, including a Ga+Cu-rich amorphous grain boundary phase and a two-stage aging treatment under inert gas pressure, to achieve uniform element distribution and amorphous grain boundary structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements (Dy) are added to increase coercivity and improve temperature stability, then the thermal stability and coercive force are improved, but the production cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters by replacing heavy rare earth elements (Dy) with light rare earth elements (Pr, Nd) and adjusting the RE content to 28-33 wt%, while optimizing B content (0.8-1.0 wt%) and adding specific amounts of Ga (0.15-0.30 wt%) and Cu (0.40-0.80 wt%). This parameter optimization achieves high coercivity and temperature stability without the high cost of heavy rare earth elements.
Solution Approach 2:
The patent substitutes expensive heavy rare earth elements (Dy, Ho) with cheaper light rare earth elements (Pr, Nd), which are more abundant and cost-effective. This replacement maintains the magnetic performance while significantly reducing material costs, making the magnet more economically viable for large-scale production.
2Reliability
If heavy rare earth compounds are added to improve coercive force and temperature stability, then the high temperature performance is improved, but the cost increases
Solution Approach 1:
The patent creates a composite microstructure consisting of RE 2 Fe 14 B main phase grains embedded in a RE-rich grain boundary phase containing Ga and Cu. This composite structure, where the grain boundary phase forms a continuous network around the main phase grains, provides both high temperature stability and improved coercivity without requiring expensive heavy rare earth compounds.
Solution Approach 2:
The patent applies local quality by concentrating Ga and Cu specifically in the grain boundary phase rather than uniformly distributing them throughout the magnet. The grain boundary region contains 3-8 wt% Ga and 6-12 wt% Cu, creating a localized composition that enhances thermal stability and coercivity at the grain boundaries where it is most needed, while keeping the overall cost down.
3Ease of manufacture
If conventional production processes are used, then the manufacturing process is simple, but the grain boundary phases are uneven leading to reduced magnet performance and stability
Solution Approach 1:
The patent applies preliminary action by adding Ga and Cu to the melt before solidification occurs. During the casting process, Ga (0.15-0.30 wt%) and Cu (0.40-0.80 wt%) are incorporated into the alloy melt along with the rare earth elements. This preliminary mixing ensures that Ga and Cu are uniformly distributed in the liquid phase before solidification, leading to uniform grain boundary phase formation without requiring complex post-processing steps.
Solution Approach 2:
The patent uses an inert atmosphere (argon or nitrogen) during the melting and casting process to prevent oxidation of the reactive rare earth elements and ensure uniform distribution of Ga and Cu in the grain boundary phase. This controlled environment maintains the chemical integrity of the alloy components and promotes homogeneous microstructure formation.
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 magnet exhibits improved magnetic properties and temperature stability with a uniform grain boundary phase, enhancing coercivity and thermal stability while reducing production costs.
Implementation Method 1
a rapid cooling process, the enrichment of Cu is suppressed, and the simultaneous enrichment of Ga and Cu is achieved
Implementation Method 2
the low melting point characteristic of Nd-Cu is utilized to improve the liquid phase fluidity of the grain boundary phase
Implementation Method 3
By introducing an inert gas to a certain pressure during the two-stage aging and cooling stages, the flow of the grain boundary phase during the aging and thermal-insulation process is promoted
Implementation Method 4
Two-stage aging treatment was performed on the sintered magnet, in which primary aging treatment was first performed at 850℃ for 3h and then rapidly cooled; then secondary aging treatment was performed at a temperature of 490℃ for 3h
Implementation Method 5
sintering the green body in a vacuum sintering furnace, and then performing an aging treatment
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
Provided are a NdFeB magnet with high-performance and high-thermal-stability and a preparation method thereof, and relates to the technical field of a NdFeB magnet. The NdFeB magnet of the present application includes a main phase Re2Fe14B, a grain boundary phase containing Re and a rare earth-rich phase, where the grain boundary phase includes a first grain boundary phase and a second grain boundary phase, the first grain boundary phase is a Ga+Cu-rich amorphous phase at a grain boundary triangle region, and the second grain boundary phase is a Ga+Cu-rich amorphous grain boundary phase formed among adjacent main phase grains, and a mass content ratio of Cu to Ga in the magnet is 1.8 to 10. The present application improves the thermal stability of the magnet by transforming the Re-rich grain boundary phase into an amorphous phase.