Dy Tb Diffusion in NdFeB Sintered Magnets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The diffusion of Dy and Tb into the grain boundary phase of Nd—Fe—B sintered magnets is hindered by residual carbon from lubricants, leading to poor workability and reduced magnetic properties, as the existing methods struggle to efficiently diffuse these elements without affecting the magnetic orientation and coercive force.
Innovation Solution
A method involving the adherence of Dy and/or Tb to the surface of sintered magnets with an average grain size of 4 μm to 8 μm, followed by heat treatment to disperse them into the grain boundary phase, utilizing vacuum vapor processing to ensure efficient diffusion and maintain high magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy and Tb are added to improve grain magnetic anisotropy, then coercive force is improved, but maximum energy product is reduced
Solution Approach 1:
The patent applies local quality by concentrating Dy and Tb elements specifically at the grain boundaries rather than uniformly distributing them throughout the magnet. This localized addition at grain boundaries improves coercive force through enhanced grain magnetic anisotropy while minimizing the overall concentration of these elements, thereby preserving the maximum energy product of the bulk material.
2Strength
If a thick film of Dy and Tb is deposited to ensure sufficient diffusion, then coercive force is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent optimizes the thickness parameter of the Dy and Tb film to a specific range (0.1-5 μm) that provides sufficient diffusion into grain boundaries to improve coercive force, while avoiding excessive thickness that would increase manufacturing complexity and cost. This parameter optimization balances performance improvement with manufacturing feasibility.
3Adaptability or versatility
If the sintered magnet is fabricated into a predetermined shape, then the magnet can be used in desired products, but defects and strains are introduced that deteriorate magnetic properties
Solution Approach 1:
The patent performs diffusion treatment of Dy and Tb elements into the grain boundaries before the magnet is fabricated into its final predetermined shape. This preliminary action strengthens the grain boundaries in advance, making the magnet more resistant to defects and strains that will occur during subsequent fabrication processes, thereby preserving magnetic properties while enabling product applicability.
4Strength
If Dy and Tb are diffused into grain boundary phase to strengthen nucleation type coercive force generation, then coercive force is dramatically improved, but the surface of the magnet may deteriorate
Solution Approach 1:
The patent uses local quality by depositing Dy and Tb elements as a thin film on the surface and controlling diffusion to occur primarily at the grain boundaries beneath the surface. This localized diffusion approach strengthens the grain boundaries for improved coercive force while limiting the depth of element penetration, thereby preserving the surface quality and appearance of the magnet.
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
This approach enables efficient diffusion of Dy and/or Tb into the grain boundary phase, resulting in high productivity and magnetic properties, including enhanced coercive force and remanent flux density, while avoiding the deterioration of the magnet's surface and improving workability.
Implementation Method 1
heat treatment at a predetermined temperature; and to thereby homogeneously diffuse the Dy and Tb that have been deposited (formed into thin film) on the surface into the grain boundary phase of the magnet
Implementation Method 2
heating the evaporating material containing at least one of Dy and Tb, the evaporating material being disposed in a same or another processing chamber; causing the evaporated evaporating material to be adhered to the surface of the sintered magnet
Data Source
AI summary
There is provided a method of manufacturing a permanent magnet in which Dy and/or Tb adhered to the surface of a sintered magnet containing a lubricant can be efficiently diffused and in which the permanent magnet having high magnetic properties can be manufactured at good productivity. The permanent magnet is manufactured by executing a first step of adhering at least one of Dy and Tb to at least a part of a surface of a sintered magnet made by sintering iron-boron-rare earth based alloy raw meal powder containing a lubricant; and a second step of heat-treating the sintered magnet at a predetermined temperature to thereby disperse at least one of Dy and Tb adhered to the surface of the sintered magnet into grain boundary phase of the sintered magnet. At this time, as the sintered magnet, there is used one manufactured in an average grain size within a range of 4 μm˜8 μm.