Nd-Fe-B Magnet Grain Boundary Composition for Higher Coercivity
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Solution Overview
Problem
The reduction of intrinsic coercivity (Hcj) in R-T-B-based permanent magnet materials is caused by the introduction of carbon during the preparation process, which forms neodymium carbide, leading to a contradictory need to reduce carbon content while it is inevitably introduced due to the use of raw materials and additives.
Innovation Solution
The R-T-B-based permanent magnet material comprises specific components including Cu, Ti, and C at the grain boundary, forming a Cu—Ti—C grain boundary phase that inhibits Nd—C formation and provides diffusion channels, enhancing Hcj through treatments like grain boundary diffusion with Tb or Dy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional preparation process with raw materials and additives is used, then the magnet can be manufactured, but carbon content increases forming neodymium carbide and reducing intrinsic coercivity
Solution Approach 1:
Cu-Ti-C grain boundary phase acts as an intermediary between the Nd2Fe14B matrix and carbon, preventing direct formation of harmful Nd-C carbides. The grain boundary phase serves as a buffer that controls carbon distribution and prevents carbon from attacking the Nd-rich regions, thus maintaining high intrinsic coercivity while allowing conventional manufacturing processes
Solution Approach 2:
The invention creates a composite structure with Cu-Ti-C grain boundary phase embedded in the Nd2Fe14B matrix. This composite approach allows the system to benefit from both the magnetic properties of the Nd2Fe14B phase and the protective/functional properties of the Cu-Ti-C grain boundary phase, achieving high coercivity despite the presence of carbon from conventional processing
2Reliability
If carbon content is reduced to prevent neodymium carbide formation, then intrinsic coercivity is improved, but manufacturing complexity increases due to stricter material purity requirements
Solution Approach 1:
The invention converts the harmful effect of carbon (which would normally form detrimental Nd-C carbides) into a beneficial component by incorporating it into the Cu-Ti-C grain boundary phase. The carbon that would otherwise be harmful is now part of the protective grain boundary structure, allowing conventional raw materials with typical carbon levels to be used without compromising coercivity
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 Cu—Ti—C grain boundary phase increases Hcj by 1162 kA/m with Tb diffusion and 883 kA/m with Dy diffusion, effectively addressing the reduction of intrinsic coercivity.
Implementation Method 1
grain boundary diffusion with Tb or Dy
Data Source
AI summary
Disclosed are an R-T-B-based permanent magnet material, a preparation method therefor and the use thereof. The R-T-B-based permanent magnet material I comprises the following components: 29.0-32.5% of R including RH, 0.30 to 0.50 wt. % of Cu, 0.05 to 0.20 wt. % of Ti, 0.85 to 1.05 wt. % of B, 0.1 to 0.3 wt. % of C, 66 to 68 wt. % of Fe, wherein R is a rare earth element and R at least includes Nd; and RH is a heavy rare earth element and RH at least includes Tb or Dy, A Cu—Ti—C grain boundary phase is formed in the R-T-B-based permanent magnet material I, and Hcj is significantly improved.