R-T-B Permanent Magnet Voids Pin Domain Walls
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Solution Overview
Problem
R-T-B based permanent magnets, particularly hot deformed magnets, face a challenge in achieving high coercivity and residual magnetic flux density due to insufficient pinning of magnetic domain walls at grain boundaries, which are composed of a soft magnetic R-rich phase, leading to reduced magnetic stability.
Innovation Solution
Intentionally forming a plurality of voids as pinning sites within the magnet, which significantly suppresses the movement of magnetic domain walls, thereby enhancing coercivity while maintaining or increasing residual magnetic flux density by controlling the area ratio and distribution of these voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If voids are introduced as pinning sites to suppress magnetic domain wall movement, then coercivity increases, but residual magnetic flux density decreases due to reduced main phase grain volume ratio
Solution Approach 1:
The invention intentionally introduces voids (porosity) into the grain boundary phase of the R-T-B based permanent magnet. These voids serve as pinning sites that effectively suppress magnetic domain wall movement, thereby increasing coercivity. The voids are formed by controlling the grain boundary phase composition and processing conditions, creating a controlled porous structure that enhances magnetic stability without compromising the main phase grain integrity
Solution Approach 2:
The invention applies local quality by creating a heterogeneous structure where the grain boundary phase contains voids while the main phase grains remain dense and intact. This localized porosity is confined to the grain boundaries, allowing the main phase grains to maintain their magnetic properties and volume ratio, thus preserving residual magnetic flux density while achieving enhanced coercivity through domain wall pinning at the void-containing grain boundaries
2Ease of manufacture
If the grain boundary phase is composed of soft magnetic R-rich phase, then the magnet can be manufactured by hot deformation, but the pinning of magnetic domain walls is insufficient leading to reduced coercivity
Solution Approach 1:
The invention creates a composite grain boundary phase structure that combines the soft magnetic R-rich phase with intentionally introduced voids. This composite structure maintains the manufacturability benefits of the R-rich phase (enabling hot deformation processing) while adding the coercivity-enhancing effect of voids that serve as pinning sites. The dual-nature grain boundary phase thus achieves both ease of manufacture and improved magnetic performance
Solution Approach 2:
By introducing voids into the R-rich grain boundary phase, the invention transforms the homogeneous soft magnetic phase into a porous composite structure. The voids create pinning sites that significantly enhance coercivity, while the remaining R-rich phase matrix maintains the hot deformation manufacturability. This porous modification allows the grain boundary phase to simultaneously provide both processing advantages and magnetic stabilization
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 results in an R-T-B based permanent magnet with improved coercivity and residual magnetic flux density, balancing these properties within specific ranges of void area ratios and distributions, effectively pinning magnetic domain walls and stabilizing magnetization.
Implementation Method 1
the larger a difference in an intensity of an anisotropic magnetic field between a pinning site and a main phase grain is, the more a movement of a magnetic domain wall is likely to be suppressed due to pinning of the magnetic domain wall
Data Source
AI summary
An R-T-B based permanent magnet includes a rare-earth element R, a transition metal element T, and B. The R-T-B based permanent magnet includes at least Nd as R. The R-T-B based permanent magnet includes at least Fe as T. The R-T-B based permanent magnet contains a plurality of main phase grains and a plurality of voids. The plurality of main phase grains includes at least R, T, and B. An area ratio of the plurality of voids in an arbitrary cross-section of the R-T-B based permanent magnet is larger than 0.2% and 2% or smaller.