NdFeB Magnet Grain Boundary Engineering with Ce-La
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Solution Overview
Problem
The incorporation of high proportions of lanthanum and cerium in NdFeB magnets negatively impacts their magnetic properties, and existing methods to improve these properties are either complex or prone to oxidation and nitride formation, making it difficult to achieve cost-effective and efficient production.
Innovation Solution
A method involving the separate preparation of alloy flakes and powders through strip casting and hydrogen embrittlement, followed by jet milling, and then mixing these with specific particle size ratios to form a Nd-rich phase that coats and penetrates Ce or La-containing grains during sintering, enhancing magnetic properties while minimizing the negative effects of lanthanum and cerium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high proportions of lanthanum and cerium are added to reduce material costs, then cost is reduced, but magnetic properties deteriorate
Solution Approach 1:
The patent divides the alloy into two separate flake components: one containing lanthanum/cerium (R1) and another without these elements (R2). This segmentation allows cost reduction through lanthanum/cerium addition while preserving magnetic properties by isolating these elements from the main magnetic phase, thus resolving the contradiction between cost and magnetic performance.
Solution Approach 2:
The invention creates local quality differentiation by having R1 flakes rich in lanthanum/cerium and R2 flakes free from these elements. During sintering, this results in localized distribution where lanthanum/cerium concentrate at grain boundaries rather than uniformly distributing throughout the magnetic phase, thereby maintaining cost-effectiveness while preserving local magnetic properties.
2Reliability
If surface grain boundary diffusion or intergranular addition of elements is carried out to improve magnetic properties, then magnetic properties are improved, but process complexity increases
Solution Approach 1:
The patent performs preliminary action by pre-separating the alloy into R1 and R2 flakes with specific compositions before sintering. This preliminary segmentation eliminates the need for complex post-sintering diffusion processes, as the desired element distribution is already established in the flake structure, thus improving magnetic properties while simplifying the overall process.
3Reliability
If lanthanum and cerium powder is added to substitute neodymium-rich phase, then cost is reduced and magnetic properties are improved, but oxidation and nitride formation occur
Solution Approach 1:
The invention creates a composite structure using two types of alloy flakes (R1 and R2) with different compositions. The R1 flakes containing lanthanum/cerium are combined with R2 flakes that provide protective elements, forming a composite material system where the interaction between components prevents oxidation and nitride formation while maintaining improved magnetic properties and cost reduction.
4Reliability
If NdHx powder is added to form hard magnetic layer, then coercive force is improved, but process complexity and dehydrogenation difficulty increase
Solution Approach 1:
Instead of using complex NdHx powder that requires dehydrogenation treatment, the patent employs a simpler alternative: R2 alloy flakes that directly provide the necessary elements during sintering. This approach achieves the same coercive force improvement without the complexity of hydrogen handling and dehydrogenation processes, effectively replacing a complex short-living object with a more stable, easier-to-handle material.
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
This method effectively improves the magnetic properties of NdFeB magnets by forming a hard magnetic layer outside Ce or La-containing grains, reducing the adverse effects of lanthanum and cerium while maintaining a cost-effective production process.
Implementation Method 1
separately subjecting the flakes of alloy R1 and the flakes of alloy R2 to a hydrogen embrittlement process
Implementation Method 2
followed by pulverizing the process product to alloy powders by jet milling
Implementation Method 3
subjecting the mixed powders to molding and magnetic field orientation, cold isostatic pressing, sintering, and an annealing process
Implementation Method 4
subjecting the mixed powders to molding and magnetic field orientation, cold isostatic pressing, sintering, and an annealing process
Data Source
AI summary
The disclosure refers to a method for preparing NdFeB magnets including at least one of Ce and La. The method includes:S1) Separately preparing flakes of alloy R1 and flakes of alloy R2 each by a strip casting process, wherein the alloy R1 includes at least one of La and Ce, but the alloy R2 does not include La and Ce;S2) separately subjecting the flakes of alloy R1 and R2 to a hydrogen embrittlement process followed by pulverizing the process product to alloy powders by jet milling, wherein a ratio of the average particle sizes D50 of the powder of alloy R1 and R2 satisfied formula:0.32≤R2/R1≤0.66;S3) mixing the powder of alloy R1 and R2; andS4) subjecting the mixed powders to molding and magnetic field orientation, cold isostatic pressing, sintering, and an annealing process.