R-T-B Permanent Magnet Composition for High Br and Hcj
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Solution Overview
Problem
R-T-B based rare earth permanent magnet materials face a trade-off between achieving high intrinsic coercivity (Hcj) and residual magnetic flux density (Br), making it difficult to maintain both properties at a high level simultaneously, and the use of expensive medium and heavy rare earth elements like Dy and Tb is not resource-efficient.
Innovation Solution
The addition of 0.30 wt. % or more of Cu and 0.05-0.20 wt. % of Ti in R-T-B based permanent magnet materials allows part of Ti to form a high-Cu-rich-Ti phase at the grain boundary, which enhances grain boundary diffusion and improves Hcj, while maintaining a Br of ≥14.30 kGs and Hcj of ≥24.1 kOe, thereby achieving simultaneous improvement of both properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If medium and heavy rare earths (Dy, Tb) are added to enhance Hcj, then Hcj is improved, but Br decreases and production cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific elements (Cu: 0.30-0.50 wt.%, Ti: 0.05-0.20 wt.%, Co: 0.10-1.0 wt.%) to the R-T-B magnet formulation. These compositional changes enable the formation of a high-Cu-high-Ti phase at grain boundaries that dissolves during sintering to create Cu-rich and Ti-rich regions, achieving enhanced Hcj through modified microstructure rather than relying on Dy/Tb addition, thereby maintaining high Br
Solution Approach 2:
The invention creates a composite microstructure within the R-T-B magnet by forming a high-Cu-high-Ti phase at grain boundaries that subsequently dissolves to produce a dual-phase structure with Cu-rich regions and Ti-rich regions. This composite approach at the microstructural level achieves both high Hcj (≥24.1 kOe) and high Br (≥14.30 kGs) simultaneously, avoiding the trade-off inherent in simple alloying with Dy/Tb
2Reliability
If Cu and Ga are added to improve Hcj, then Hcj is improved, but sintering temperature decreases and sintering denseness deteriorates
Solution Approach 1:
The invention merges Cu and Ti into a combined high-Cu-high-Ti phase at the grain boundaries rather than allowing them to act independently. This combined phase dissolves during sintering to create a synergistic effect where Cu enriches at grain boundaries to enhance Hcj while Ti prevents excessive grain growth. The merging of these elements' functions allows maintaining higher sintering temperatures and achieving better sintering denseness compared to using Cu or Ga alone
3Reliability
If Ti is added to improve Hcj, then Hcj is improved, but a Ti-rich phase with high melting point forms and grain boundary diffusion effect deteriorates
Solution Approach 1:
The invention creates local quality differentiation by forming a high-Cu-high-Ti phase specifically at the grain boundaries, which then dissolves to create Cu-rich regions at grain boundaries and Ti-rich regions in the matrix. This localized distribution ensures that Cu is positioned where it can most effectively enhance Hcj through grain boundary diffusion, while Ti provides overall microstructural stability. The local quality approach prevents the formation of a uniform high-melting-point Ti-rich phase that would hinder diffusion
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 R-T-B based permanent magnet material exhibits excellent performance with Br≥14.30 kGs and Hcj≥24.1 kOe, outperforming conventional formulations by forming a high-Cu-high-Ti phase that can be completely dissolved in grain boundary diffusion, leading to improved Hcj and maintaining high Br levels.
Implementation Method 1
part of Ti enters the grain boundary to form high-Cu-rich-Ti phase
Implementation Method 2
these phases can be completely dissolved in the grain boundary diffusion
Data Source
AI summary
A rare earth permanent magnet material and a raw Material composition, a preparation method therefor and use thereof. The rare earth permanent magnet material comprises the following components in percentage by mass: 29.0-32.0 wt. % of R, where R comprises RH, and the content of RH is greater than 1 wt. %; 0.30-0.50 wt. % of Cu (not including 0.50 wt. %); 0.10-1.0 wt. % of Co; 0.05-0.20 wt. % of Ti; 0.92-0.98 wt. % of B; and the remainder being Fe and unavoidable impurities; wherein R is a rare-earth element and at least comprises Nd; and RH is a heavy rare-earth element and at least comprises Tb. The R-T-B system permanent magnet material exhibits excellent performance, wherein Br≥14.30 kGs, and Hcj≥24.1 kOe. The invention can synchronously improve Br and Hcj.