R-T-B Permanent Magnet Composition With Low Heavy Rare Earth Content
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Solution Overview
Problem
Existing R-T-B based permanent magnets face challenges in maintaining excellent corrosion resistance and magnetic properties, particularly coercive force at room and high temperatures, while minimizing heavy rare earth element content.
Innovation Solution
The R-T-B based permanent magnet composition includes specific elements within defined ranges, featuring a rare earth element content of 28.50 to 31.50 mass %, a heavy rare earth element content of 0.30 mass % or less, and a unique distribution of heavy rare earth elements decreasing from the surface inwards, along with a grain boundary structure containing an R—Fe—Co—Ga—Al concentrated portion, which enhances magnetic properties and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth element content is increased to improve coercive force at room and high temperatures, then magnetic properties improve, but material cost increases and corrosion resistance may deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements within the permanent magnet structure. Specifically, the heavy rare earth element concentration is optimized in the grain boundary phase rather than being uniformly distributed throughout the entire magnet. This localized concentration strategy allows the heavy rare earth elements to exert their maximum effect on coercive force at critical interfaces while minimizing the overall quantity required, thereby reducing material cost and improving corrosion resistance.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (rare earth elements, Fe, Co, Al, Zr, Ga, B, C) in specific proportions to create a multi-phase structure with R2T14B main phase grains and grain boundary phase. This composite approach allows the system to achieve high coercive force through synergistic interactions between different elements and phases, reducing dependence on heavy rare earth element content alone while maintaining excellent magnetic properties and corrosion resistance.
2Quantity of substance
If heavy rare earth element content is decreased to reduce cost, then material cost decreases, but coercive force at room and high temperatures deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements within the permanent magnet structure. Specifically, the heavy rare earth element concentration is optimized in the grain boundary phase rather than being uniformly distributed throughout the entire magnet. This localized concentration strategy allows the heavy rare earth elements to exert their maximum effect on coercive force at critical interfaces while minimizing the overall quantity required, thereby reducing material cost and improving corrosion resistance.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (rare earth elements, Fe, Co, Al, Zr, Ga, B, C) in specific proportions to create a multi-phase structure with R2T14B main phase grains and grain boundary phase. This composite approach allows the system to achieve high coercive force through synergistic interactions between different elements and phases, reducing dependence on heavy rare earth element content alone while maintaining excellent magnetic properties and corrosion resistance.
3Reliability
If grain boundary structure is optimized with R-Fe-Co-Ga-Al concentrated portion to improve magnetic properties, then coercive force and squareness improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the grain boundary phase, specifically the concentrations of R, Fe, Co, Ga, and Al elements. By optimizing these compositional parameters within specific ranges, the patent achieves improved coercive force and squareness. This approach transforms the complex structural optimization problem into a more manageable compositional parameter control problem, which can be achieved through standard metallurgical processing techniques.
Solution Approach 2:
The patent applies local quality by creating a non-uniform distribution of heavy rare earth elements within the permanent magnet structure. Specifically, the heavy rare earth element concentration is optimized in the grain boundary phase rather than being uniformly distributed throughout the entire magnet. This localized concentration strategy allows the heavy rare earth elements to exert their maximum effect on coercive force at critical interfaces while minimizing the overall quantity required, thereby reducing material cost and improving corrosion resistance.
Data Source
AI summary
An R-T-B based permanent magnet has a heavy rare earth element content of 0.30 mass % or less excluding 0 mass %. The R-T-B based permanent magnet is either an R-T-B based permanent magnet including at least a rare earth element, Fe, Co, Al, Zr, Ga, B, and C within predetermined ranges; or an R-T-B based permanent magnet including main phase grains including crystal grains having an R2T14B type crystal structure and a grain boundary between two or more of the main phase grains adjacent to each other, having an R—Fe—Co—Ga—Al concentrated portion in the grain boundary.