R-T-B Magnet Grain Boundary Segmentation for Corrosion and Magnetic Trade-offs

The patent applies local quality by creating an R-Ga-Co-Cu-N concentrated part specifically at the grain boundaries, while the crystal grains maintain their R2T14B structure. This localized modification at the grain boundaries provides corrosion resistance without compromising the magnetic properties of the main crystal grains. The concentrated part has a different composition and function than the bulk material, with Ga, Cu, and N specifically enriched at the grain boundaries to form a protective layer.

The patent creates a composite structure consisting of R2T14B crystal grains embedded in an R-Ga-Co-Cu-N concentrated grain boundary phase. This composite approach combines the high magnetic properties of the R2T14B phase with the corrosion resistance provided by the Ga-Co-Cu-N enriched grain boundaries. The two-phase composite structure allows simultaneous optimization of magnetic performance and corrosion resistance.

The patent localizes the rare earth elements R at the grain boundaries through the formation of R-Ga-Co-Cu-N concentrated parts, rather than having them uniformly distributed. This localized concentration at grain boundaries protects the interior of the crystal grains from hydrogen absorption while maintaining the necessary magnetic properties. The Ga-Co-Cu-N phase acts as a barrier that prevents hydrogen from penetrating into the R-containing crystal grains.

The R-Ga-Co-Cu-N concentrated part at the grain boundaries acts as an intermediary layer between the external environment and the R2T14B crystal grains. This intermediate phase, enriched with Ga, Cu, and N, serves as a protective barrier that mediates the interaction between hydrogen and the rare earth elements, preventing direct contact and hydrogen absorption while maintaining magnetic performance.

The patent modifies only the grain boundary regions with R-Ga-Co-Cu-N concentration while leaving the crystal grain interiors unchanged. This localized modification ensures that the magnetic properties, which are determined by the crystal grain structure, are preserved. The Ga-Co-Cu-N enrichment occurs specifically at the grain boundaries where it provides corrosion protection without interfering with the magnetic ordering within the grains.

The patent segments the magnet structure into distinct crystal grains with R2T14B structure and grain boundaries with R-Ga-Co-Cu-N concentration. This segmentation allows independent optimization of each region: the crystal grains are optimized for magnetic properties while the grain boundaries are optimized for corrosion resistance. The clear separation between these functional regions prevents the compromise of magnetic properties during corrosion protection modification.