R-T-B Rare Earth Magnet Alloy Coercive Force Optimization
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Solution Overview
Problem
Existing R-T-B-based rare earth sintered magnets face challenges in achieving a sufficiently large coercive force without increasing the amount of Dy, as adding metal elements like Al, Si, Ga, and Sn often requires higher Dy concentrations, leading to supply issues and decreased coercive force when Si exceeds 5%.
Innovation Solution
The development of an alloy with a main phase primarily containing R2Fe14B and a grain boundary phase having a high concentration of rare earth elements and a transition metal-rich phase with a lower concentration of rare earth elements and a higher concentration of transition metal elements, where the volume ratio of the transition metal-rich phase is increased, allowing for optimal B concentration and Dy proportion to maximize coercive force without increasing Dy content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy is increased to improve coercive force, then coercive force is improved, but resource availability deteriorates and supply becomes limited
Solution Approach 1:
The invention changes the compositional parameters by adding specific metal elements (Al: 0.1-3.0 wt%, Si: 0.1-3.0 wt%, Ga: 0.1-1.0 wt%, Sn: 0.1-1.0 wt%) to the R-T-B alloy system. These parameter changes enable the formation of a transition metal-rich phase that improves coercive force without requiring increased Dy content, thus resolving the contradiction between strength improvement and resource availability
Solution Approach 2:
The invention creates a composite microstructure consisting of a main phase (R2Fe14B) and a transition metal-rich phase formed by the addition of Al, Si, Ga, and/or Sn. This composite structure allows the transition metal-rich phase to contribute to coercive force enhancement, reducing dependency on Dy and resolving the supply limitation issue
2Strength
If Si is increased to improve coercive force, then coercive force is improved, but when Si exceeds 5%, coercive force decreases
Solution Approach 1:
The invention optimizes the Si content parameter within a specific range (0.1-3.0 wt%) and combines it with other metal elements (Al, Ga, Sn) to achieve the desired coercive force. This controlled parameter change prevents Si from exceeding the critical 5% threshold while still obtaining the beneficial effects on coercive force
Solution Approach 2:
The invention creates a multi-element composite system where Si works synergistically with Al, Ga, and/or Sn to form the transition metal-rich phase. This composite approach distributes the functional requirements across multiple elements, preventing any single element (including Si) from exceeding its optimal concentration and causing degradation
3Strength
If metal elements (Al, Si, Ga, Sn) are added to improve coercive force, then coercive force is improved, but Dy concentration must be increased
Solution Approach 1:
The invention forms a transition metal-rich phase through the addition of Al, Si, Ga, and/or Sn, which creates a composite microstructure where the transition metal-rich phase contributes to coercive force enhancement. This allows the base alloy to maintain lower Dy concentration while achieving the desired magnetic properties
Solution Approach 2:
The invention changes the alloy composition parameters by adding specific amounts of metal elements (Al: 0.1-3.0 wt%, Si: 0.1-3.0 wt%, Ga: 0.1-1.0 wt%, Sn: 0.1-1.0 wt%) to create the transition metal-rich phase. This parameter modification enables coercive force improvement through the new phase formation rather than through increased Dy concentration
Data Source
AI summary
An alloy for R-T-B-based rare earth sintered magnets which contains R which is a rare earth element; T which is a transition metal essentially containing Fe; a metallic element M containing one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied,0.0049Dy+0.34≤B/TRE≤0.0049Dy+0.36 Formula 1wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.