Abstract: In a typical sintered multi-component Sm₂Co₁₇-type magnet with strong fiber texture, we show that the distributions of grain boundary precipitates (GBPs) are heavily dependent on the grain boundary (GB) geometry with respect to the texture direction, which has significant effects on domain wall pinning. Results demonstrate that the continuous GBPs turn into discrete upon the angle between {0001} planes and GB increases from 0° to 90°, meanwhile the GBPs thickness and precipitation free zones (PFZs) width both increase linearly by a factor of 2.5-4. Transmission electron microscopy (TEM) reveals that the GBPs are alternatively stacked Cu-rich SmCo₅ and Zr-rich Sm_n+1Co_5n-1 (n = 2,3,4) compounds, while the PFZs are composed of 2:17R and intermediate 2:17R’ phases. Atomic-level elemental mappings and first-principles calculations indicate that Cu exists at the Co-2c site in the SmCo₅ forming SmCo₃Cu₂ and Zr locates at the dumbbell Sm-6c sites in the Sm_n+1Co_5n-1. The symbiotic GBPs have orientation relationships of [0001]_GBPs//[0001]_2:17R and [$10\bar{1}0$]_GBPs//[$2\bar{1}\bar{1}0$]_2:17R. The formation of anisotropic GBPs is owing to the strong fiber texture, i.e., the larger angle between {0001} planes and GBs, the more {0001} diffusion channels for atoms to GBs, resulting in discrete and thick GBPs. In-situ Lorentz TEM shows that the domain walls interrupted by GBPs migrate easily under applied magnetic fields. Possible approaches to enhance the magnetic hardness via tuning the GBs are proposed.

Key words: Sm₂Co₁₇ magnets, Grain boundary precipitate, TEM Domain wall, Texture