Rare Earth Magnet Production via Core-Shell Infiltration
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Solution Overview
Problem
Existing methods struggle to enhance the coercive force of R-T-B-based rare earth magnets while minimizing magnetization reduction, particularly when the particle diameter of the main phase is between 1 to 20 μm, as the formation of a core/shell structure is difficult to achieve with conventional infiltration methods.
Innovation Solution
A production method involving the preparation of specific alloy melts, cooling, pulverization, and sintering processes to create a core/shell structure in the main phase without relying on a grain boundary phase, where the first alloy powder with a particle diameter of 1 to 20 μm is directly contacted with a melt of similar composition to form a core/shell structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a penetrating material is caused to infiltrate inside a precursor having a main phase and an R-rich grain boundary phase, then the coercive force is enhanced, but magnetization is reduced
Solution Approach 1:
The invention extracts and removes the R-rich grain boundary phase from the precursor, allowing the penetrating material to directly contact the main phase without the grain boundary phase interference. This enables the formation of a core/shell structure where the penetrating material forms a shell around the main phase core, enhancing coercive force while preserving magnetization by eliminating the need for penetrating material to diffuse through the grain boundary phase.
Solution Approach 2:
The invention creates a non-uniform structure by forming a core/shell configuration where the main phase has different composition zones: a core region and a shell region formed by the penetrating material. This local differentiation allows the shell part to enhance coercive force while the core part maintains high magnetization, resolving the contradiction between these two properties.
2Volume of moving object
If the particle diameter of the main phase is from 1 to 20 μm, then the magnet has larger grain size, but a core/shell structure cannot be formed by conventional infiltration methods
Solution Approach 1:
The invention performs preliminary removal of the grain boundary phase before introducing the penetrating material. This preliminary action creates direct contact between the penetrating material and the main phase surface, enabling efficient formation of the core/shell structure even in large-grained materials (1-20 μm) where conventional infiltration methods fail due to the blocking effect of the grain boundary phase.
3Ease of manufacture
If a light rare earth element (Ce, La, Y) is used to reduce cost, then the magnetization is originally low, but magnetization undergoes serious reduction due to penetrating material
Solution Approach 1:
The invention removes the grain boundary phase that would otherwise require penetrating material infiltration, thereby preventing the serious magnetization reduction that occurs when penetrating material diffuses into light rare earth element-containing main phases. This extraction approach allows cost-effective use of light rare earth elements while preserving their magnetic properties.
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 enhances the coercive force of rare earth magnets while suppressing magnetization reduction, even when the particle diameter of the main phase is large, by forming a core/shell structure without the intervention of a grain boundary phase.
Implementation Method 1
cooling the melt of the first alloy at a rate of 100 to 102 K/sec to obtain a first alloy ingot
Implementation Method 2
putting the first alloy powder into contact with the melt of the second alloy
Implementation Method 3
preparing a melt of a first alloy
Data Source
AI summary
A method for producing a rare earth magnet, including preparing a melt of a first alloy having a composition represented by (R1vR2wR3x)yTzBsM1t (wherein R1 is a light rare earth element, R2 is an intermediate rare earth element, R3 is a heavy rare earth element, T is an iron group element, and M1 is an impurity element, etc.), cooling the melt of the first alloy at a rate of from 100 to 102 K/sec to obtain a first alloy ingot, pulverizing the first alloy ingot to obtain a first alloy powder having a particle diameter of 1 to 20 μm, preparing a melt of a second alloy having a composition represented by (R4pR5q)100-uM2u (wherein R4 is a light rare earth element, R5 is an intermediate or heavy rare earth element, M2 is an alloy element, etc.), and putting the first alloy powder into contact with the melt of the second alloy.