Dy-Tb Diffused NdFeB Magnet Grain Boundary Engineering
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Solution Overview
Problem
Nd—Fe—B sintered magnets suffer from demagnetization at high temperatures and deterioration of magnetic properties due to defects and strains, and the use of Dy and Tb to improve coercivity reduces the maximum energy product, while being scarce and costly.
Innovation Solution
A method involving the evaporation of metal evaporating materials containing Dy, Tb, and Pr onto the surface of Nd—Fe—B sintered magnets, followed by heat treatment to diffuse these elements into grain boundary phases, with additional elements like Al, Cu, and Ga to enhance diffusion velocity and coercivity, and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy and Tb are added to improve coercive force, then grain magnetic anisotropy is improved, but maximum energy product is reduced
Solution Approach 1:
The patent applies local quality by concentrating Dy and Tb diffusion specifically at grain boundary phases rather than uniformly throughout the magnet. The grain boundary regions receive higher concentrations of these elements to enhance local magnetic anisotropy and coercive force, while the grain interior maintains its original composition and high magnetic properties, thus resolving the contradiction between improved coercivity and preserved energy product.
Solution Approach 2:
The patent segments the magnet into two distinct regions: grain boundary phases and grain interiors. By applying different compositions to these segments (Dy/Tb-enriched boundaries, Nd-rich interiors), the patent achieves both high coercive force at boundaries and high maximum energy product in grains, effectively resolving the technical contradiction.
2Strength
If Dy and Tb are deposited in thick films to improve coercivity, then grain magnetic anisotropy is enhanced, but manufacturing cost increases due to scarce resources
Solution Approach 1:
The patent uses partial action by depositing thin films (3-10 nm) of Dy and Tb, which is insufficient to form continuous thick layers but adequate to achieve effective diffusion into grain boundaries. This partial deposition reduces material consumption and cost while still achieving the desired coercive force improvement through targeted diffusion at critical grain boundary regions.
Solution Approach 2:
The patent changes the deposition parameters from conventional thick film deposition to ultra-thin film deposition (3-10 nm), and changes the processing parameters by using specific heat treatment conditions (temperature and time) to achieve controlled diffusion. These parameter changes enable effective coercivity improvement with minimal material usage, reducing manufacturing cost.
3Stability of the object's composition
If conventional heat treatment is used to diffuse Dy and Tb, then diffusion occurs, but diffusion velocity is slow and productivity is reduced
Solution Approach 1:
The patent changes the heat treatment parameters by optimizing temperature (800-1000°C) and time (1-24 hours) to achieve effective diffusion velocity. The combination of ultra-thin initial film deposition with controlled heat treatment creates optimal diffusion conditions that maintain compositional homogeneity while significantly improving diffusion velocity and productivity compared to conventional methods.
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 method results in permanent magnets with higher coercive force and magnetic properties, improved productivity, and reduced costs, while maintaining high magnetic properties and corrosion resistance without the need for additional materials like Co.
Implementation Method 1
a film-forming step of evaporating metal evaporating material containing at least one of Dy and Tb and adhering evaporated metal atoms to a surface of an iron-boron-rare earth sintered magnet
Implementation Method 2
evaporating metal evaporating material containing at least one of Dy and Tb and adhering evaporated metal atoms to a surface
Implementation Method 3
a diffusing step of performing heat treatment to diffuse metal atoms adhered to the surface into grain boundary phases of the sintered magnet
Implementation Method 4
performing heat treatment to diffuse metal atoms adhered to the surface
Data Source
AI summary
A permanent magnet is provided which has formed a Dy, Tb film on a surface of an iron-boron-rare earth sintered magnet of a predetermined shape, with diffusion thereof into grain boundary phases, having a higher coercive force. The method of manufacturing a permanent magnet includes a film-forming step of evaporating metal evaporating material containing at least one of Dy and Tb and adhering evaporated metal atoms to a surface of the iron-boron-rare earth sintered magnet, and a diffusing step of performing heat treatment to diffuse metal atoms adhered to the surface into grain boundary phases of the sintered magnet. The metal evaporating material contains at least one of Nd and Pr.