(1. 北京有色金属研究总院， 北京 100088;
2. 中国科学院 金属研究所 固体原子象开放研究实验室， 沈阳 110015;
3. 清华大学 核能技术设计研究院， 北京 100084)
摘 要: 使用AEM和HREM研究了添加纳米SiC颗粒和同时添加纳米SiC颗粒及SiC晶须的两种Si3N4复合陶瓷材料的微观组织和断裂机制。结果表明，部分SiC颗粒分布在Si3N4晶内，SiC晶须分布在Si3N4晶粒之间，SiC颗粒和晶须与Si3N4界面之间不存在第二相组织，非晶组织大多分布在Si3N4三叉晶界。断裂裂纹主要沿晶界和相界面扩展，也可能穿过少数Si3N4晶粒。当裂纹扩展遇到SiC颗粒和/或SiC晶须时，会发生转弯，产生分枝裂纹或微裂纹并在Si3N4晶内和Si3N4晶粒的断裂表面引起晶格畸变，这降低了裂纹扩展能量，从而改善复合陶瓷材料的断裂强度和断裂韧性。
关键字: Si3N4复合陶瓷； 微观组织； 裂纹扩展；断裂机制
（1. General Research Institute for Nonferrous Metals， Beijing 100088， P.R.China;
2. Laboratory of Atomic Imaging of Solid， Institute of Metal Research，The Chinese Academy of Science， Shenyang 110015， P.R.China;
3. Institute of Nuclear Energy Technology, Tsinghua University，Beijing 100084， P.R.China）
Abstract:The microstructure and fracture mechanism of the Si3N4composite ceramics with the addition of nano SiC powder， and nano SiC powder and SiC whisker were studied with AEM and HREM. A part of SiC particles distribute in the interior of Si3N4 grain， the SiC whiskers distribute between the Si3N4 grains and most of the amorphous structure is at the triple grain junction of the Si3N4. There is no second phase in the interface between the SiC particle， whisker and Si3N4. Fracture cracks expand mainly along the interface， also may pass through small amount of Si3N4 grains. Crack expanding direction is changed and branching crack and microcrack is created when the crack expanding meets the SiCparticle and/or whisker. The lattice distortion is produced in the Si3N4andfractured surface layer of S3N4， that will decrease the expanding energy ofcrackand so improve fracture strength and fracture toughness of the composite ceramics.
Key words: Si3N4 composite ceramic； microstructure； crack expanding； fracture mechanism
