Core-Shell R-T-B Permanent Magnet Material for High Coercivity
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Solution Overview
Problem
Conventional methods for producing NdFeB permanent magnets face challenges in achieving high coercivity and energy product while maintaining remanence, often requiring large amounts of heavy rare earth elements, which increases costs and limits application in high-performance devices.
Innovation Solution
An R-T-B based permanent magnet material with a 'core-shell' structure is developed, where a heavy rare earth film is plated on alloy flakes, followed by crushing, grinding, and diffusion sintering, allowing for uniform distribution of heavy rare earth elements to form a shell layer, thereby enhancing coercivity without compromising remanence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements are added to increase coercivity, then coercivity is improved, but remanence deteriorates and production cost increases
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at grain boundaries through the formula designed by Professor Deng, rather than uniform distribution throughout the magnet. This localized concentration at critical interfaces provides maximum coercivity enhancement with minimal overall heavy rare earth content, preserving bulk remanence properties.
Solution Approach 2:
The patent employs composite material strategy by creating a multi-phase structure consisting of NdFeB main phase combined with grain boundary phases containing heavy rare earth elements. This composite approach allows each phase to contribute its specific properties: the NdFeB phase provides high remanence while the grain boundary phases provide coercivity enhancement.
2Strength
If heavy rare earth elements are added to increase coercivity, then coercivity is improved, but production cost increases
Solution Approach 1:
By localizing heavy rare earth elements to grain boundaries through the specific formula design, the patent minimizes the total quantity of expensive heavy rare earth materials required while achieving maximum coercivity effect at the most critical locations, thereby reducing overall production cost.
Solution Approach 2:
The patent optimizes the precise composition parameters of the alloy, controlling the exact ratios of rare earth elements, transition metals, and main phase components. This parameter optimization ensures efficient utilization of heavy rare earth elements, achieving high coercivity with minimal material consumption and cost.
3Strength
If grain boundary diffusion technique is used to increase coercivity, then coercivity is improved, but production cycle time increases
Solution Approach 1:
The patent incorporates heavy rare earth elements directly into the initial alloy formulation designed by Professor Deng, rather than applying them as a post-processing step. This preliminary incorporation eliminates the need for separate diffusion treatments and extends, thereby reducing the overall production cycle.
Solution Approach 2:
The patent merges the alloying process with the grain boundary modification process by integrating heavy rare earth element incorporation into the base alloy formula. This consolidation of processes eliminates sequential steps, reducing total production time while achieving the same coercivity enhancement effect.
4Strength
If grain boundary diffusion technique is used to increase coercivity, then coercivity is improved, but diffusion depth is limited
Solution Approach 1:
The patent achieves effective grain boundary modification by localizing heavy rare earth elements precisely at grain boundary interfaces through the designed formula. This localized approach ensures that even with limited diffusion depth, the critical grain boundary regions are adequately modified to provide sufficient coercivity enhancement.
Solution Approach 2:
The patent optimizes diffusion parameters including temperature, time, and composition ratios to achieve adequate heavy rare earth element distribution at grain boundaries. By carefully controlling these parameters, sufficient diffusion depth is achieved to modify grain boundaries effectively without requiring excessive diffusion distances.
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 significantly increases coercivity and maintains high energy product with reduced heavy rare earth content, simplifying the production process and avoiding long diffusion heat treatments, enabling the production of magnets with improved performance.
Implementation Method 1
a heavy rare earth film is plated on alloy flakes
Implementation Method 2
followed by crushing, grinding, and diffusion sintering, allowing for uniform distribution of heavy rare earth elements to form a shell layer
Implementation Method 3
diffusion sintering
Data Source
AI summary
The present invention relates to an R-T-B based permanent magnet material, having a composition of RxTyTmqBz (at. %), wherein 13≤x≤15.5, 0.5≤q≤3, 0.85≤z≤1, y=100−x−q−z; wherein R is LRaHR1-a, LR is one selected from the group consisting of Pr, Nd, PrNd, or a combination thereof, HR is one selected from the group consisting of Dy and Tb, or a combination thereof, and 0.95≤a≤1; wherein T is one selected from the group consisting of Fe and Co, or a combination thereof; and Tm is a transition metal. The advantage of the method is that: plating a heavy rare earth film on alloy flakes using a magnetron sputtering device, and the coercivity of the magnet is significantly increased simply by having a “core-shell” structure without long time diffusion heat treatment.