The microstructure of twinning as well as the phase boundary between 1:5H and 2:17R phase in Fe-rich Sm₂Co₁₇-type magnets was characterized at atomic scale using nanobeam diffraction and high-resolution STEM-HAADF imaging, and the reason for the dramatic increase of coercivity during slow cooling was investigated based on the microchemistry analysis. The twinning relationship in the 2:17R phase originates from ordered substitution of Sm atoms by Co–Co atomic pairs on every three ($\overline{3}$033) and (30$\overline{3}$3) planes, leading to formation of two corresponding equivalent twin variants. The basal plane of the 2:17R phase, the 1:3R platelet phase across the 2:17R cell and the 1:5H cell boundary phase between two adjacent 2:17R cells all can act as effective twin boundary. The cell boundary phase is precipitated along the pyramidal habit plane, and a fully coherent phase boundary (PB) is formed between the 1:5H and 2:17R phases with the orientation relationship to be PB//(11$\overline{2}$1)_1:5H//(10$\overline{1}$1)_2:17R. The phase boundary may either be parallel to or intersect with the pyramidal planes occupied by Co–Co atomic pairs. The substantial increase of coercivity during slow cooling is ascribed to the development of large gradient of the elements concentration within the cell boundary phase, resulting in large gradient of domain wall energy, and thus the pinning strength of the cell boundary phase against magnetic domain wall motion is significantly enhanced.

使用纳米束衍射和高分辨率 STEM-HAADF 成像在原子尺度上表征了富铁 Sm ₂ Co ₁₇型磁体中孪晶的微观结构以及 1:5H 和 2:17R 相之间的相界，以及原因基于显微化学分析研究了缓冷过程中矫顽力的急剧增加。2:17R 相中的孪生关系源于 Sm 原子被 Co-Co 原子对每三个（$\overline{3}$033) 和 (30$\overline{3}$3) 平面，导致形成两个相应的等效孪生变体。2:17R相的基面、穿过2:17R细胞的1:3R血小板相和两个相邻的2:17R细胞之间的1:5H细胞边界相都可以作为有效的孪生边界。胞界相沿锥体习性面析出，1:5H和2:17R相之间形成完全相干的相界(PB)，取向关系为PB//(11$\overline{2}$1) _1:5H //(10$\overline{1}$1) _2:17R。相界可以平行于或与 Co-Co 原子对占据的金字塔平面相交。缓冷过程中矫顽力的显着增加归因于晶胞边界相内元素浓度的大梯度发展，导致畴壁能量梯度大，从而导致晶胞边界相对磁畴壁运动的钉扎强度显着增强。