NdFeB Magnet Grain Boundary Segregation Reduces Heavy Rare Earth Cost
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Solution Overview
Problem
Current methods for producing high-performance NdFeB permanent magnets rely heavily on expensive heavy rare earth elements, leading to increased costs and potential decreases in remanence with additive alloys, and often alter the magnet structure to improve coercivity.
Innovation Solution
A sintered NdFeB magnet composition featuring a main phase, a shell structure, grain boundary phase, and specific rich regions, produced through strip casting, hydrogen treatment, jet milling, and sintering, which maintains high remanence and coercivity without excessive heavy rare earth usage, achieved by controlling the composition and structure of the additive alloy to form a shell structure and optimize grain boundary distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements are used to improve coercivity, then magnetic performance is enhanced, but production cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters by replacing heavy rare earth elements (Dy, Tb) with light rare earth elements (Pr, Nd) and non-rare earth elements (Ga, Cu, Al). Specifically, the additive alloy contains Pr (30-40 wt%), Nd (10-20 wt%), Ga (5-15 wt%), Cu (5-15 wt%), and Al (5-15 wt%), fundamentally altering the material composition to reduce cost while maintaining performance
Solution Approach 2:
The patent creates a composite material system combining light rare earth elements with specific non-rare earth elements (Ga, Cu, Al) in the additive alloy. This composite approach leverages the synergistic effects of different elements: Pr and Nd for magnetic properties, Ga and Cu for grain boundary control and coercivity enhancement, and Al for structural stability, achieving cost-effective high-performance magnets
2Reliability
If grain boundary diffusion method is used to improve coercivity, then magnetic performance is enhanced, but production cost increases
Solution Approach 1:
The patent applies preliminary action by pre-alloying the additive elements (Pr, Nd, Ga, Cu, Al) into a homogeneous additive alloy before the sintering process. This pre-mixed alloy is then distributed throughout the compact, and during sintering, the elements automatically segregate to grain boundaries through diffusion. This eliminates the need for separate, complex post-sintering diffusion treatment steps, significantly simplifying manufacturing while achieving the desired grain boundary composition
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 effectively enhances magnetic properties, particularly remanence and coercivity, while significantly reducing the use of heavy rare earth elements and production costs, maintaining high performance with a cost-effective process.
Implementation Method 1
controlling the composition and structure of the additive alloy to form a shell structure and optimize grain boundary distribution
Implementation Method 2
produced through strip casting, hydrogen treatment, jet milling, and sintering
Data Source
AI summary
The disclosure discloses a NdFeB permanent magnet and a preparation method thereof. The magnet is composed of main phase I, a shell structure, a grain boundary phase adjacent to the shell structure, a main phase II, a Ga rich region and a Cu rich region. The magnet has high remanence, high coercivity, and high magnetic energy. In addition, this method can significantly reduce the production cost.