Rare Earth Magnet Microstructure for High-Temperature Coercivity
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Solution Overview
Problem
Rare earth based sintered magnets experience demagnetization at high temperatures, limiting their application in hybrid vehicles and other high-temperature environments, despite methods to improve coercivity at room temperature, such as replacing Nd with heavy rare earth elements and adding Cu, which face resource limitations and residual magnetic flux density decreases.
Innovation Solution
The microstructure of R2T14B main-phase crystal grains with a higher number density of fine products in the interior than the periphery, and grain boundary phases with a thickness of 5-200 nm, effectively pinning magnetic domain walls and suppressing demagnetization by controlling the distribution and segregation of elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If part of Nd in Nd2Fe14B is replaced with heavy rare earth elements such as Dy and Tb, then coercivity at room temperature is improved, but residual magnetic flux density decreases and resource availability is limited
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of fine products within the crystal grains. The interior region contains a higher density of fine products compared to the periphery, allowing localized magnetic domain wall pinning where it is most needed while preserving the overall magnetic properties of the material. This resolves the contradiction by improving coercivity locally without sacrificing residual magnetic flux density globally.
Solution Approach 2:
The patent creates a composite microstructure within the R2T14B main phase by forming fine products (segregated regions with different composition) distributed throughout the crystal grains. This internal composite structure provides magnetic domain wall pinning sites that enhance coercivity while the surrounding R2T14B matrix maintains high residual magnetic flux density, thus resolving the technical contradiction.
2Strength
If Cu is added to form liquid phase in grain boundary, then coercivity at room temperature is improved, but resource availability and manufacturing complexity increase
Solution Approach 1:
The patent extracts the grain boundary phase from the composition design by making it Cu-free or low-Cu. Instead of relying on Cu-added liquid phase at grain boundaries, the invention achieves coercivity improvement through fine products formed within the main phase crystal grains. This simplifies manufacturing by eliminating or reducing Cu addition while maintaining effective magnetic domain wall pinning.
3Strength
If fine products are formed only in main-phase grains, then magnetic domain wall pinning is enhanced, but nuclei for reverse magnetic domain generation increase
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of fine products within the crystal grains. The interior region contains a higher density of fine products compared to the periphery, allowing localized magnetic domain wall pinning where it is most needed while preserving the overall magnetic properties of the material. This resolves the contradiction by improving coercivity locally without sacrificing residual magnetic flux density globally.
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
Significantly reduces the rate of demagnetization at high temperatures, enabling the magnets to maintain performance in high-temperature environments while avoiding resource limitations and maintaining residual magnetic flux density.
Implementation Method 1
fine magnetically hardening products of a non-magnetic phase are formed in the grains of the main phase R2T14B, and thus magnetic domain wall pinning is performed, thereby improving the coercivity
Implementation Method 2
By replacing part of Nd with the heavy rare earth elements, the magneto-crystalline anisotropy is increased, and as a result, the coercivity of the Nd—Fe—B based sintered magnet at a room temperature can be sufficiently improved
Data Source
AI summary
The present invention provides a rare earth based magnet having a microstructure in which in a section of the R2T14B main-phase crystal grains, the number density of the fine products in the interior of (inside) the crystal grains is larger than that in the periphery of (outside) the crystal grains. That is, the rare earth based magnet includes R2T14B main-phase crystal grains and grain boundary phases formed between the R2T14B main-phase crystal grains. The R2T14B main-phase crystal grains include a substance where fine products are formed in the crystal grains. In the section of the main-phase crystal grains, when the crystal grains are divided into the interior of the crystal grains and the periphery of the crystal grains with a specific ellipse, the fine products are formed such that the number density in the interior is larger than that in the periphery.