Block Magnets with Uniform Core-Shell Microstructure Regenerated from NdFeB Grain Boundary Diffusion Sheet Magnets.

Area of Science:

• Materials Science
• Metallurgy
• Magnetism

Background:

• Grain boundary diffusion (GBD) is effective for incorporating heavy rare earth elements into NdFeB magnets.
• Recycling GBD magnets is challenging due to their uneven microstructure.

Purpose of the Study:

• To investigate the short-loop recycling of GBD NdFeB sheet magnets into block magnets.
• To compare the recyclability and magnetic properties of GBD magnets versus conventional sintered magnets.

Main Methods:

• Comparative analysis of GBD and sintered NdFeB magnets.
• Regeneration sintering of GBD NdFeB sheet magnets into block magnets.
• Microstructural analysis using electron microscopy and elemental mapping.

Main Results:

• Regenerated GBD magnets showed higher coercivity than conventional magnets despite lower initial heavy rare earth content.
• Microstructural analysis revealed uniform distribution of core-shell grains and Tb elements in regenerated GBD magnets.
• Enhanced grain boundary isolation due to uniform Tb shells and reduced RE-rich phase enrichment.

Conclusions:

• Short-loop recycling of GBD NdFeB sheet magnets is a viable method for producing high-coercivity block magnets.
• This recycling process facilitates uniform heavy rare earth element distribution, improving magnetic properties.
• Offers a new strategy for achieving high coercivity with reduced heavy rare earth element usage in bulk magnets.