R-T-B Sintered Magnet Yttrium Segregation Corrosion Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
R-T-B based sintered magnets suffer from low corrosion resistance due to oxidation of rare earth elements, leading to hydrogen adsorption in the grain boundary phase and a decrease in magnetic properties, while reducing carbon content to enhance corrosion resistance compromises magnetic field orientation and residual flux density.
Innovation Solution
Incorporating yttrium (Y) into the R-T-B based sintered magnet with a specific molar ratio of R1 to Y (80:20 to 35:65) in the grain boundary phase to inhibit hydrogen adsorption and enhance corrosion resistance, thereby maintaining good magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of carbon in the magnet alloys is reduced to enhance corrosion resistance, then corrosion resistance is improved, but the orientation of magnet powders in the molded body decreases and residual flux density Br reduces
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling carbon content to 0.03 mass% or less and adding specific elements (Co: 3-12 mass%, Al: 0.01-1.0 mass%, Cu: 0.01-1.0 mass%) to achieve both improved corrosion resistance and maintained magnetic properties without compromising powder orientation
Solution Approach 2:
The invention creates a composite grain boundary phase structure containing multiple elements (Co, Al, Cu, and rare earth elements) that work synergistically to provide both corrosion resistance and magnetic property enhancement, replacing the simple carbon-based approach
2Reliability
If Y is added to the R-T-B based sintered magnet to improve corrosion resistance, then corrosion resistance is enhanced, but the magnetic properties may deteriorate if the ratio is not optimized
Solution Approach 1:
The invention optimizes the compositional parameters by specifying that Y content in rare earth element R is 5-70 at% with R1 content of 25-75 at%, creating the optimal balance between corrosion resistance and magnetic properties in the grain boundary phase
Solution Approach 2:
The invention applies local quality by specifically targeting the grain boundary phase composition, where Y and other elements segregate to provide corrosion protection at the grain boundaries while maintaining the magnetic properties of the main R2Fe14B phase grains
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 approach significantly improves corrosion resistance and maintains excellent magnetic properties by segregating Y in the grain boundary phase, preventing corrosion and hydrogen adsorption, while optimizing the R1 to Y ratio ensures stable magnetic performance.
Implementation Method 1
the action that hydrogen produced by the corrosion reaction is adsorbed into the grain boundary can be efficiently inhibited by the oxidization of segregated Y
Implementation Method 2
hydrogen is adsorbed into the grain boundary phase in grain boundary
Data Source
AI summary
The present invention provides a permanent magnet with both a high corrosion resistance and magnetic properties compared to the existing R-T-B based magnets. It is a R-T-B based sintered magnet (wherein, R includes Y (yttrium) and R1 as essential, R1 is at least one kind of rare earth elements except Y but includes Nd as essential, and T is at least one kind of transition metal element including Fe or the combination of Fe and Co as essential). By allowing the ratio of R1 to Y (R1:Y) in the R contained in the grain boundary phase to be 80:20˜35:65 in terms of the calculated molar ratio of the grain boundary phase and adding Y to the raw materials of the R-T-B based magnet, Y segregates at the triple point, and corrosion of grain boundary phase is prevented by oxidized Y.