Intergranular Phase Engineering in Nd-Fe-B Magnets: Achieving Deep Dy Diffusion through Cu-Modified Grain Boundaries

Area of Science:

• Materials Science
• Magnetism
• Nanotechnology

Background:

• Grain boundary diffusion (GBD) enhances coercivity in Nd-Fe-B magnets.
• Challenges exist in achieving sufficient diffusion depth for thick magnets.

Purpose of the Study:

• Investigate the impact of different copper (Cu) addition methods on GBD processed Nd-Fe-B magnets.
• Optimize microstructure and magnetic properties for enhanced performance.

Main Methods:

• Explored three Cu incorporation strategies: surface diffused, grain boundary-doped, and melt-added.
• Utilized DyH3 nanopowder as a diffusion source for enhanced GBD.
• Analyzed microstructural changes and magnetic property improvements.

Main Results:

• Melt-added Cu created a uniform grain boundary network, widening grain boundaries and improving magnetic isolation.
• Optimized grain boundaries increased Dy diffusion depth from 401 to 593 μm.
• Melt-added Cu magnets showed a coercivity increment of 11.76 kOe after Dy GBD, significantly higher than Cu-free magnets.

Conclusions:

• Copper addition, particularly via the melt-added method, optimizes grain boundaries for enhanced GBD in Nd-Fe-B magnets.
• This strategy successfully improves coercivity in thick (10 mm) magnets while maintaining squareness.
• The findings enable GBD application in thick magnets for demanding applications like high-temperature wind turbines.