R-T-B Magnet Alloy Composition and Grain Boundary Control
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Solution Overview
Problem
R-T-B-based rare earth sintered magnets face challenges in achieving high coercive force and orientation rate due to limitations in Dy resources and the adverse effects of impurities like Si, which also affect the coercive force when added in excess.
Innovation Solution
An alloy composition with a specific range of R, T, and B concentrations, including a transition metal-rich phase, where the boron concentration is lower than theoretical, and the addition of metals like Al, Ga, and Cu, with a heat treatment process to optimize grain boundary phase distance and phase composition, allowing for high coercive force and orientation rate without relying on Dy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy is added to improve coercive force, then coercive force increases, but resource availability decreases and cost increases
Solution Approach 1:
The invention changes the compositional parameters by precisely controlling B content (4.5-6.2 at%) and R content (13-16 at%), and by controlling the distance between grain boundary phases (3-11 μm) to achieve high coercive force without Dy addition
Solution Approach 2:
The invention replaces expensive Dy with cheaper and more abundant elements (Al, Ga, Cu) as additives, and uses readily available R-T-B alloy composition to achieve the desired magnetic properties
2Strength
If Si is added to improve coercive force, then coercive force increases, but when Si exceeds 5%, coercive force decreases
Solution Approach 1:
The invention changes the approach by controlling B content to a specific range (4.5-6.2 at%) and adding different metal elements (Al, Ga, Cu) instead of relying on Si, thereby avoiding the harmful effect of excess Si while still improving coercive force
Solution Approach 2:
The invention uses metal elements (Al, Ga, Cu) as intermediary substances that facilitate grain boundary phase formation and improve coercive force without the harmful effects associated with Si impurities
3Quantity of substance
If B concentration is increased to achieve R2T14B composition, then main phase proportion increases, but coercive force decreases due to R2T17 phase formation
Solution Approach 1:
The invention changes the B concentration parameter to a lower range (4.5-6.2 at%) compared to theoretical R2T14B composition, and controls R content (13-16 at%) to prevent R2T17 phase formation while maintaining high main phase proportion and achieving high coercive force
Solution Approach 2:
The invention creates a modified composition that copies the beneficial aspects of R2T14B (high main phase proportion) while avoiding the harmful aspect (R2T17 phase formation at higher B content)
4Strength
If Dy concentration is increased to achieve high coercive force, then coercive force increases, but manufacturing cost and resource dependency increase
Solution Approach 1:
The invention changes the compositional parameters by controlling R content (13-16 at%), B content (4.5-6.2 at%), and adding metal elements (Al, Ga, Cu) to achieve high coercive force without Dy, thereby improving manufacturing stability and reducing resource dependency
Solution Approach 2:
The invention replaces Dy with cheaper and more readily available metal elements (Al, Ga, Cu) and optimized R-T-B composition, making manufacturing more stable and less dependent on scarce resources
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 solution enables the production of R-T-B-based magnets with improved coercive force and orientation rate, effectively reducing the need for Dy and minimizing the impact of impurities, resulting in enhanced magnetic properties.
Implementation Method 1
a heat treatment process to optimize grain boundary phase distance and phase composition
Implementation Method 2
a heat treatment process to optimize grain boundary phase distance and phase composition
Data Source
AI summary
In an alloy for an R-T-B-based rare earth sintered magnet of the present invention formed of a rare earth element R, a transition metal T containing Fe as a main component, a metal element M containing one or more types of metals selected from Al, Ga, and Cu, and B and inevitable impurities, 13 at % to 16 at % of R is contained, 4.5 at % to 6.2 at % of B is contained, 0.1 at % to 2.4 at % of M is contained, the balance is T and the inevitable impurities, a proportion of Dy in the entire rare earth element is 0 at % to 65 at %, Formula 1 described below is satisfied, a main phase containing R2Fe14B and an alloy grain boundary phase containing more R than the main phase are included, and a distance between the alloy grain boundary phases is greater than or equal to 3 μm and less than or equal to 11 μm.0.30≤B/TRE≤0.37 (Formula 1)