Vibration-Assisted PVD Coating for NdFeB Magnets
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Solution Overview
Problem
Conventional methods for producing permanent magnets, such as sintered neodymium-iron-boron (Nd—Fe—B) magnets, require high amounts of expensive and rare dysprosium (Dy) and terbium (Tb) to achieve desired magnetic properties, leading to inefficient distribution and increased costs.
Innovation Solution
A method involving physical vapor deposition to coat alloy powders with neodymium, iron, and boron with a non-uniform distribution of dysprosium and/or terbium, using vibration during the coating process to achieve a higher surface concentration of these elements, reducing the overall amount needed while maintaining magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to distribute Dy or Tb uniformly in grains and grain boundaries, then magnetic properties are maintained, but the amount of Dy or Tb required is high (6-10 wt%)
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of Dy or Tb, with higher concentration at grain boundaries and lower concentration in grain interiors. This is achieved through specific processing conditions that promote segregation of rare earth elements to grain boundaries during solidification, allowing reduced overall Dy/Tb content while maintaining magnetic properties through optimized boundary phase composition.
Solution Approach 2:
The patent changes processing parameters (cooling rate, holding time, temperature) to control the distribution of Dy or Tb. By adjusting these parameters, the rare earth elements are selectively concentrated at grain boundaries rather than uniformly distributed, reducing the total amount needed while maintaining the necessary magnetic properties through enhanced boundary phase effectiveness.
2Reliability
If Dy or Tb are added to mixed metals before melting and alloying for uniform distribution, then magnetic properties are achieved, but costs increase due to high Dy/Tb consumption
Solution Approach 1:
Instead of uniform distribution through conventional alloying, the patent creates localized high concentration of Dy or Tb at grain boundaries. This non-uniform distribution achieves the necessary magnetic properties with reduced overall rare earth content, directly lowering material costs while maintaining performance.
Solution Approach 2:
The patent modifies processing parameters (cooling rate, holding time, temperature profile) to control element distribution. These parameter changes enable selective segregation of Dy/Tb to grain boundaries during solidification, reducing total rare earth requirements and associated costs while achieving target magnetic properties.
3Quantity of substance
If surface coating with Dy or Tb is applied to reduce bulk content, then Dy/Tb usage is reduced by up to 90%, but achieving uniform and controlled distribution is difficult
Solution Approach 1:
The patent creates controlled local enrichment of Dy or Tb at grain boundaries through processing parameter optimization, achieving the desired non-uniform distribution with high precision. This approach provides better control over where the rare earth elements end up compared to surface coating methods, ensuring consistent magnetic properties.
Solution Approach 2:
By precisely controlling processing parameters (cooling rate, holding time, temperature), the patent achieves reproducible and controlled distribution of Dy or Tb at grain boundaries. This parameter control provides superior manufacturing precision compared to surface coating techniques, ensuring consistent element placement and magnetic performance.
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 allows for a significant reduction in the use of Dy and Tb by up to 90% compared to conventional methods, achieving similar magnetic properties with a non-uniform distribution that enhances grain boundary presence, measured using scanning electron microscopy.
Implementation Method 1
The powder is vibrated during formation of the coating
Implementation Method 2
The Nd—Fe—B based powder can be coated via physical vapor deposition (PVD)
Data Source
AI summary
A method of making a permanent magnet includes a step of forming a coating on an alloy powder by physical vapor deposition. The alloy powder includes neodymium, iron, boron and other metals. The coating includes a component selected from the group consisting of dysprosium, terbium, iron, and the alloys thereof. The alloy powder is vibrated during formation of the coating. Finally, a permanent magnet is formed from the coated powder, the permanent magnet having a non-uniform distribution of dysprosium and/or terbium. A method of making a permanent magnet using a vibrating transport belt is also provided.