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Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion
Yaojun Lu1, Shuwei Zhong1, Munan Yang1
1Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, China.
Materials (Basel, Switzerland)
|November 28, 2019
Summary
Terbium (Tb) diffusion enhances coercivity in sintered Neodymium-Iron-Boron (Nd-Fe-B) magnets. Optimal corrosion resistance and magnetic properties are found in the sub-surface layer due to specific microstructural changes.
Area of Science:
- Materials Science
- Magnetism
- Solid-State Chemistry
Background:
- Sintered Neodymium-Iron-Boron (Nd-Fe-B) magnets are crucial for high-performance applications.
- Enhancing coercivity and temperature stability is key for advanced magnet technology.
- Grain boundary diffusion is a primary method for modifying Nd-Fe-B magnet properties.
Purpose of the Study:
- To investigate the diffusion behavior of Terbium (Tb) in sintered Nd-Fe-B magnets.
- To analyze the relationship between Tb diffusion depth, microstructure, and magnetic properties.
- To understand the stages of Tb diffusion and their impact on coercivity and corrosion resistance.
Main Methods:
- Electron Probe Micro-analyzer (EPMA) was used to analyze Tb concentration gradients and microstructures.
- Microstructural analysis was performed at different depths within the magnet.
- Diffusion mechanisms were studied to understand Tb distribution.
Main Results:
- Coercivity enhancement and temperature stability decrease with increasing Tb diffusion depth.
- Optimal corrosion resistance was observed in the sub-surface layer (300-1000 μm).
- Tb diffusion occurs in three distinct stages, forming varied RE-rich phases and core-shell structures.
Conclusions:
- Tb diffusion significantly impacts Nd-Fe-B magnet properties, with depth-dependent effects.
- The sub-surface layer exhibits a favorable balance of magnetic properties and corrosion resistance.
- Understanding the three diffusion stages is crucial for optimizing Tb-diffused Nd-Fe-B magnets.
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