NdFeB Magnet Composition for High Coercivity Without Br Loss
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Solution Overview
Problem
Neodymium-iron-boron magnetic materials exhibit relatively low intrinsic coercivity (Hcj) and are sensitive to temperature changes, limiting their application in high-temperature environments.
Innovation Solution
A neodymium-iron-boron magnetic material composition comprising specific percentages of Nd, Tb, Cu, Co, Ga, Al, Zr, and Fe, with controlled distribution of Tb and Co at grain boundaries, is prepared through a dual alloy method involving sintering and aging, enhancing Hcj and maintaining high residual magnetic flux density (Br).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth metal (Dy or Tb) is added to increase Hcj, then intrinsic coercivity is improved, but residual magnetic flux density is greatly reduced
Solution Approach 1:
The patent changes the concentration parameters of multiple elements simultaneously (Tb: 0.5-3.0 wt%, Co: 1.0-3.0 wt%, Cu: 0.1-0.5 wt%, Ga: 0.1-0.3 wt%) to achieve optimal magnetic properties. This multi-parameter optimization allows increasing Hcj while maintaining Br by coordinating the effects of different elements rather than relying on heavy rare earth addition alone
Solution Approach 2:
The patent creates a composite alloy system combining Nd-Fe-B base material with multiple additive elements (Tb, Co, Cu, Ga). This composite approach leverages the synergistic effects of different elements: Tb enhances coercivity, Co increases saturation magnetization, Cu refines microstructure, and Ga improves thermal stability, thereby resolving the trade-off between Hcj and Br
2Force
If heavy rare earth metal is added to improve Hcj, then anisotropic field increases, but the degree of improvement is limited and Br decreases
Solution Approach 1:
The patent introduces Co and Cu as intermediary elements that mediate the relationship between heavy rare earth addition and magnetic properties. Co serves as an intermediary by providing both magnetic moment enhancement and site occupation that limits heavy rare earth solubility, while Cu acts as an intermediary by controlling grain boundary phases and preventing excessive heavy rare earth aggregation, thereby optimizing both Hc and Br
3Force
If appropriate amount of heavy metal is added to increase Hcj, then intrinsic coercivity is improved, but it is difficult to maintain relatively high Br while increasing Hcj to a greater extent
Solution Approach 1:
The patent assigns multiple functions to each added element: Tb provides both coercivity enhancement and microstructure refinement, Co contributes to both saturation magnetization and grain boundary strengthening, Cu serves both as a grain boundary phase former and magnetic property enhancer, and Ga provides both thermal stability and magnetic anisotropy improvement. This multi-functionality allows comprehensive magnetic performance optimization without sacrificing Br for Hcj gain
Data Source
AI summary
A neodymium-iron-boron magnetic material, a preparation method therefor and an application thereof. The neodymium-iron-boron magnetic material comprises the following components in percentage by mass: 29.5-31.5 wt. % of R, where RH>1.5 wt. %; 0.05-0.25 wt. % of Cu; 0.42-2.6 wt. % of Co; 0.20-0.3 wt. % of Ga; 0.25-0.3 wt. % of N; 0.46-0.6 wt. % of Al, or alternatively Al is less than or equal to 0.04 wt. % but is not 0; 0.98-1 wt. % of B; and 64-68 wt. % of Fe; wherein R is a rare-earth element and comprises Nd and RH, RH is a heavy rare-earth element and comprises Tb, and a mass ratio of Tb to Co is less than or equal to 15 but is not 0. The neodymium-iron-boron magnetic material has higher Hcj and Br, and lower absolute values of temperature coefficients of Br and Hcj.