RFeB Sintered Magnet Coercivity via Cu-Al Segregation
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Solution Overview
Problem
RFeB-based sintered magnets used in fluctuating external magnetic fields require higher coercivity and squareness ratio, but existing methods struggle to achieve sufficient values and a wide annealing temperature range for optimal performance.
Innovation Solution
The composition of the RFeB-based sintered magnet includes 24-31% RL, 0.1-6.5% RH, 0.8-1.4% B, 0.03-0.2% Zr/Ti/Hf, 0.8-5.5% Co, 0.1-1.0% Cu, and 0.1-1.0% Al, with a total Cu and Al content exceeding 0.5%, and a grain boundary diffusion treatment is used to optimize the distribution of these elements, forming a paramagnetic R3(Co,Fe) phase at grain boundaries to enhance coercivity and squareness ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zr is incorporated into the raw-material alloy to prevent abnormal grain growth, then coercivity is improved, but the content range for optimal performance is narrow and manufacturing precision is difficult to control
Solution Approach 1:
The patent changes the compositional parameters by introducing Cu and Al as grain boundary segregating elements in addition to Zr. This modifies the sintering behavior and grain growth characteristics, allowing for better control of the microstructure and coercivity while maintaining the abnormal grain growth prevention effect
Solution Approach 2:
The patent creates a composite grain boundary structure by incorporating multiple elements (Zr, Cu, Al) that work synergistically. Zr prevents abnormal grain growth, while Cu and Al segregate to grain boundaries to enhance coercivity, creating a multi-functional composite material system
2Reliability
If Al and Cu are added together with Zr to enhance coercivity and temperature characteristics, then magnetic performance is improved, but the individual content ranges for Al and Cu are not established leading to manufacturing variability
Solution Approach 1:
The patent establishes specific content ranges for Al (0.01-1.0 mass%) and Cu (0.01-1.0 mass%) as independent parameters, allowing precise control of their individual contributions to grain boundary segregation and coercivity enhancement, while maintaining compatibility with Zr content
3Productivity
If Cu and Co are added in combination to widen the annealing temperature range, then production efficiency is improved, but the optimal annealing temperature range is still limited and productivity is constrained
Solution Approach 1:
The patent widens the effective annealing temperature range by optimizing the Cu content (0.01-1.0 mass%) and combining it with Co (0.5-5.0 mass%). This compositional adjustment shifts the peak coercivity temperature and broadens the temperature window where high coercivity is maintained, enabling more flexible production scheduling and higher throughput
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 approach results in RFeB-based sintered magnets with high coercivity and squareness ratio, maintaining stability across a wide range of annealing temperatures, improving magnetic performance and production efficiency.
Implementation Method 1
The incorporation of Zr prevents crystal grain growth during sintering to inhibit abnormal grain growth
Implementation Method 2
the content of Cu and the content of Al are each 0.1% by mass or higher and the total content of Cu and Al is higher than 0.5% by mass, thereby a paramagnetic R3(Co,Fe) phase is formed at grain boundaries
Implementation Method 3
the range of annealing temperatures capable of giving a high coercivity is widened
Data Source
AI summary
The present invention relates to an RFeB-based sintered magnet having a composition including: 24-31% by mass of at least one element selected from the group consisting of Nd, Pr, La and Ce; 0.1-6.5% by mass of at least one element selected from the group consisting of Dy and Tb; 0.8-1.4% by mass of B; 0.03-0.2% by mass of at least one element selected from the group consisting of Zr, Ti, Hf and Nb; 0.8-5.5% by mass of Co; 0.1-1.0% by mass of Cu; and 0.1-1.0% by mass of Al, with a remainder being Fe and unavoidable impurities, in which the composition has a total content of Cu and Al being higher than 0.5% by mass.