Blending Powder Process for Recycling Sintered Nd-Fe-B Magnets

Area of Science:

• Materials Science
• Metallurgy
• Recycling Technologies

Background:

• Growing demand for Nd-Fe-B permanent magnets necessitates efficient recycling methods due to rare-earth resource limitations.
• Current recycling processes often face challenges with material degradation and property loss.

Purpose of the Study:

• To investigate a magnet-to-magnet recycling process for sintered Nd-Fe-B permanent magnets.
• To analyze the microstructural changes and magnetic property evolution during recycling.

Main Methods:

• Utilized hydrogen decrepitation and powder blending with NdH_x for magnet recycling.
• Analyzed recycled magnet composition and microstructure using advanced characterization techniques.
• Studied the effect of mixing Dy-free and Dy-containing magnets on the final properties.

Main Results:

• Demonstrated composition inhomogeneity and a core-shell structure in recycled magnetic grains.
• Observed Dy diffusion at grain boundaries during sintering, leading to Dy-depleted/enriched zones.
• Achieved a 52% increase in coercive force for the N42 magnet grade.

Conclusions:

• The magnet-to-magnet recycling process effectively enhances magnetic properties of Nd-Fe-B magnets.
• Improved grain isolation and alignment contribute to the observed increase in coercive force and retained remanence.