R-T-B Rare Earth Magnet Grain Boundary Phase Control
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Solution Overview
Problem
Existing Nd-Fe-B based rare earth permanent magnets face challenges in maintaining high coercivity (HcJ) while preserving good remanence (Br) and squareness ratio (Hk/HcJ), with existing methods struggling to optimize sintering temperatures and grain growth.
Innovation Solution
An R-T-B based rare earth sintered magnet composition incorporating rare earth elements like Nd and Pr, iron group elements, boron, and carbon, with specific ratios of Zr, Ti, or Nb, and additional elements like Cu, Ga, and Al, forming coexisting phases at grain boundaries to enhance coercivity and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sintering temperature is increased to improve density, then manufacturing precision improves, but abnormal grain growth occurs
Solution Approach 1:
The invention applies preliminary action by pre-forming the grain boundary phase composition before sintering. The M-C compounds, M-B compounds, and 6-13-1 phases are already present in the compacted powder mixture, acting as pre-formed grain boundary structures that control grain growth during sintering. This preliminary preparation enables dense sintering at controlled temperatures without abnormal grain growth, as the pre-existing grain boundary phases regulate the sintering process.
2Ease of manufacture
If grain boundary phase composition is simplified, then ease of manufacture improves, but coercivity decreases
Solution Approach 1:
The invention applies parameter changes by precisely controlling the area ratios of different grain boundary phases: M-C compounds (30-70%), M-B compounds (5-10%), and 6-13-1 phases (25-60%). These specific compositional parameters optimize the balance between ease of manufacture and coercivity. The controlled parameter ranges ensure sufficient coercivity through effective domain wall pinning while maintaining manufacturability through a manageable phase composition that can be achieved via conventional sintering processes.
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 magnet composition effectively improves coercivity (HcJ) while maintaining good remanence (Br) and squareness ratio (Hk/HcJ), with controlled sintering and grain boundary phases optimizing magnetic properties and production stability.
Implementation Method 1
the grain boundaries include a coexisting part in which an M—C compound, an M—B compound, and a 6-13-1 phase coexist
Implementation Method 2
an object of the invention is to attain a suppressed abnormal grain growth, a wider optimum sintering temperature, and good magnetic properties
Implementation Method 3
a wider optimum sintering temperature
Data Source
AI summary
An R—T—B based rare earth sintered magnet in which R is a rare earth sintered magnet, T is an iron group element, and B is boron. R includes one or more selected from Nd and Pr. The R—T—B based rare earth sintered magnet includes M and C in which M is one ore more selected from Zr, Ti, and Nb. The R—T—B based rare earth sintered magnet includes main phase grains and grain boundaries, and the grain boundaries includes a coexisting part in which a M—C compound, a M—B compound, and a 6-13-1 phase coexist. The R—T—B based rare earth sintered magnet attains improved HcJ while maintaining good Br and Hk/HcJ.