Sm_(2)Co_(17)磁体胞状组织边缘2:17R’相的透射电子显微镜表征  

Identification of 2:17R’ Cell Edge Phase in Sm_(2)Co_(17)-Type Permanent Magnets by Transmission Electron Microscopy

作　　者：陈虹宇 宋欣 周相龙 贾文涛 袁涛 马天宇 CHEN Hongyu;SONG Xin;ZHOU Xianglong;JIA Wentao;YUAN Tao;MA Tianyu(Frontier Institute of Science and Technology and State Key Laboratory for Mechanical Behavior of Materials,Xi􀆳an Jiaotong University,Xi􀆳an 710049,China;The Southwest Applied Magnetism Research Institute,Mianyang 621000,China)

机构地区：[1]西安交通大学前沿科学技术研究院金属材料强度国家重点实验室,西安710049 [2]西南应用磁学所,绵阳621000

出　　处：《金属学报》2021年第12期1637-1644,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.52071256;金属材料强度国家重点实验室开放课题项目No.20192106。

摘　　要：结合电子衍射、TEM明/暗场像和HRTEM像从[100]_(2:17R)和[101]_(2:17R)2个晶带轴研究了具有纳米胞状组织的Sm_(25)Co_(50.2)Fe_(16.2)Cu_(5.6)Zr_(3.0)(质量分数,%)钉扎型磁体胞边缘的微结构。结果表明,胞状组织边缘存在菱方结构的2:17R’相,与ABCA 3层堆垛周期的2:17R相相比有一层{001}基面原子错排,造成畴壁能密度高于胞内的2:17R相,从而产生不利于方形度的排斥型畴壁钉扎。进一步的对比研究表明,2:17R’相的超晶格衍射斑点可覆盖实验观察到的所有卫星斑,排除了之前文献中根据部分卫星斑所认为的2:17H相或Sm_(n+1)Co_(5n-1)相。因此,本工作为理解Sm_(2)(Co,M)_(17)磁体方形度低的微结构根源提供了新证据。Pinning-controlled Sm_(2)(Co,M)_(17)(M = Fe,Cu,and Zr) magnets with cellular nanostructures are the strongest high-temperature permanent magnets.The squareness factor of such magnets is smaller than those of nucleation-controlled permanent magnets,leading to a lower-than-ideal maximum energy product.One of the main reasons for this poor squareness is that the pinning strength is weaker at cell edges than at 1:5 H cell boundaries.However,the structure of these edges remains a topic of debate.To identify the microstructure of cell edges,electron diffraction,TEM bright/dark field imaging,and HRTEM imaging on a model magnet Sm_(25)Co_(50.2)Fe_(16.2)Cu_(5.6) Zr_(3.0)(mass fraction,%) were performed using both [100]_(2:17) Rand [101]_(2:17) Rzone axes.The results revealed a rhombohedral 2:17 R’ phase at some of the edges,with one faulting basal layer in the 2:17 R lattice.Further comparative investigations revealed that all the extra superlattice reflections result from the 2:17 R’ phase,excluding the previously identified2:17 H or Sm_(n + 1) Co_(5 n-1) or their mixture that can only produce a part of such superlattice reflections.Owing to the 2:17 R’ phase with a faulted basal plane,the free energy at the cell edges is higher than that of the 2:17 R cell interiors,leading to repulsive domain-wall-pinning unfavorable for the squareness factor.This study provides important evidence for understanding the microstructural origin of the poor squareness factor obtained for Sm_(2)(Co,M)_(17) permanent magnets.

关 键 词：永磁材料 Sm-Co磁体 电子衍射 缺陷 TEM表征 

分 类 号：TG113.12[金属学及工艺—物理冶金]