It is still an open debate whether the 1:5H cell boundaries (CBs) or the intersections of 1:3R platelets and 1:5H CBs are the strong pining sites for the cellular nanostructured 2:17-type Sm-Co-Fe-Cu-Zr high temperature permanent magnets despite that they have been widely applied in advanced industries since 1970s. Herein, through tuning the volume fraction of Zr-enriched 1:3R platelets by varying the second-step aging time, the pinning behavior in a model magnet Sm₂₅Co_44.9Fe_21.5Cu_5.6Zr_3.0 (wt%) was investigated. The results show that the volume fraction of 1:3R platelets can be effectively enlarged without changing the cell size (i.e. the volume fraction of CBs) by extending the aging time at 400 °C. Microscopic TEM characterizations combined with macroscopic magnetic measurements reveals that the locally thickened 1:3R platelets after long-term second-step aging reduce the effective pinning area by interrupting the magnetic domain walls at CBs, weakening the average pinning strength and the coercivity of the magnet. Consequently, our work supports that the 1:5H CBs act as the dominating pinning sites instead of the intersections of 1:3R platelets and 1:5H CBs, which may provide an important insight towards understanding the hard magnetism of pinning-controlled permanent magnets.

1:5H 细胞边界 (CBs) 或 1:3R 血小板与 1:5H CBs 的交叉点是否是细胞纳米结构 2:17 型 Sm-Co-Fe-Cu 的强钉扎位点仍然是一个公开的争论-Zr 高温永磁体，尽管它们自 1970 年代以来已广泛应用于先进工业。在此，通过改变第二步时效时间来调整富 Zr 1:3R 片晶的体积分数，模型磁体中的钉扎行为 Sm ₂₅ Co _44.9 Fe _21.5 Cu _5.6 Zr _3.0(wt%) 进行了研究。结果表明，通过延长400°C的老化时间，可以有效增大1:3R血小板的体积分数，而不会改变细胞大小（即CBs的体积分数）。微观 TEM 表征结合宏观磁性测量表明，长期第二步老化后局部增厚的 1:3R 小片通过中断 CB 处的磁畴壁来减少有效钉扎面积，削弱了磁铁的平均钉扎强度和矫顽力. 因此，我们的工作支持 1:5H CB 作为主要的钉扎位点，而不是 1:3R 血小板和 1:5H CB 的交叉点，这可能为理解钉扎控制的永磁体的硬磁性提供重要的见解。