Ti-Containing NdFeB Magnet With TiB2 Grain-Boundary Coercivity Control
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Solution Overview
Problem
Existing sintered NdFeB magnets face challenges in maintaining coercivity (HcJ) at high temperatures due to irreversible thermal demagnetization, and there is a need to minimize the use of heavy rare-earth elements while enhancing coercivity and magnetic performance.
Innovation Solution
A Ti-containing NdFeB magnet is developed with a uniform distribution of nanoscale needle-like TiB2 crystals in the thin-layer grain boundary phase, controlled through a segmented sintering process to enhance coercivity and squareness, using a method that includes molding, sintering, and aging processes to optimize TiB2 crystal distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare-earth elements (Dy, Tb) are diffused into the magnet to enhance coercivity, then coercivity (HcJ) is improved, but the cost increases and the complexity of the process increases
Solution Approach 1:
The patent extracts the essential function of heavy rare-earth elements (enhancing coercivity) and transfers it to a different material system (Ti-B alloy). Instead of using Dy or Tb diffusion, the invention uses Ti and B elements that form TiB2 precipitates at grain boundaries, achieving similar coercivity enhancement without the need for heavy rare-earth elements, thereby simplifying the material composition and reducing cost
Solution Approach 2:
The patent replaces expensive heavy rare-earth elements (Dy, Tb) with cheaper Ti and B elements. The Ti-B alloy powder serves as a cost-effective alternative that provides the necessary coercivity enhancement through TiB2 precipitate formation, eliminating the need for expensive heavy rare-earth element diffusion processes
2Quantity of substance
If Ti is added to NdFeB alloy to reduce heavy rare-earth usage, then cost is reduced, but the ability to further enhance coercivity is limited
Solution Approach 1:
The patent creates a composite structure where TiB2 precipitates are formed within the NdFeB matrix at grain boundaries. This composite approach combines the benefits of Ti addition (cost reduction, heavy rare-earth substitution) with the coercivity-enhancing effect of TiB2 precipitates, achieving both cost reduction and maintained/high coercivity performance
Solution Approach 2:
The patent applies local quality by concentrating Ti and B elements specifically at the grain boundaries through the formation of TiB2 precipitates. This localized distribution ensures that the coercivity enhancement occurs precisely where needed (at grain boundaries) while minimizing the overall Ti content required, thus balancing cost reduction with performance maintenance
3Reliability
If TiB2 crystals are formed in the grain boundary phase, then coercivity is enhanced, but the distribution uniformity and crystal size control become challenging
Solution Approach 1:
The patent applies preliminary action by pre-mixing Ti and B elements into the NdFeB alloy powder before sintering. This ensures that Ti and B are uniformly distributed throughout the powder mixture prior to the sintering process, which facilitates uniform TiB2 precipitate formation at grain boundaries during sintering, thereby achieving consistent coercivity enhancement across the magnet
Solution Approach 2:
The patent utilizes parameter changes by optimizing the sintering temperature and holding time to control TiB2 precipitate formation. By carefully controlling these thermal parameters, the patent achieves uniform TiB2 distribution and appropriate crystal size (0.5-2.0 μm), balancing coercivity enhancement with manufacturing precision
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
The Ti-containing NdFeB magnet exhibits high coercivity and squareness with excellent magnetic properties, achieving improved thermal stability and reduced reliance on heavy rare-earth elements.
Implementation Method 1
diffusing heavy rare-earth elements (such as Dy, Tb, etc.) from the surface of the magnet into its interior, allowing these elements to concentrate in the outer shell region of the main phase grains
Implementation Method 2
aging the sintered compact to obtain the magnet
Data Source
AI summary
A Ti-containing NdFeB magnet includes main phase grains, thin-layer grain boundary phases, and triangular region grain boundary phases. TiB2 crystals are contained in the Ti-containing NdFeB magnet. A total number N of TiB2 crystals in the Ti-containing NdFeB magnet, a number N1 of TiB2 crystals distributed in the main phase grains, and a number N2 of TiB2 crystals in the triangular region grain boundary phases satisfy 0≤N1/N≤0.05 and 0≤N2/N≤0.3.