的组织形成机制
( 1. 哈尔滨工业大学 材料科学与工程学院， 哈尔滨 150001；
2. 香港城市大学 物理及材料科学系，香港)
摘 要: 采用B或B2O3、 TiO2和Al粉反应热压制备了原位 (Al2O3+TiB2+Al3Ti)/Al复合材料，采用光学显微镜、 扫描电镜和透射电镜分析了原位复合材料的显微组织。 热压状态下， 反应生成相Al3Ti呈大块不规则形状， 尺寸约几十微米； Al2O3和TiB2为细小弥散质点， TEM分析发现TiB2颗粒呈六边形， 而Al2O3颗粒呈等轴状。在以Al粉、 TiO2粉和B粉为原料制备的复合材料中， 除反应生成了大块的Al3Ti相外, 还有细小针状Al3Ti相沉淀析出， 且呈弥散分布。热挤压后大块的Al3Ti被破碎成细小弥散质点。 Al2O3在TiO2和B2O3粉末表面生成； TiB2在B或B2O3粉表面形成， 因而均呈弥散分布，且尺寸细小。 自TiO2中还原出的Ti溶入液态Al中形成Al3Ti时， Ti可在液态Al中长距离扩散， 因而Al3Ti呈大块不规则状。
关键字: 反应热压； Al基复合材料； Al2O3; TiB2; Al3Ti; 显微组织
composites fabricated by reaction hot pressing
（ 1. School of Materials Science and Engineering,
Harbin Institute of Technology, Harbin 150001, China;
2. Department of Physics and Material Science,
City University of Hong Kong, Kowloon, Hong Kong, China）
Abstract: Two (Al2O3+TiB2+Al3Ti)/Al composites were made from Al-B2O3-TiO2 and Al-B-TiO2 raw powders by hot pressing. The microstructure of the two composites was analyzed by OM, SEM and TEM. The results show that coarse Al3Ti blocks with size of several tens of micrometers are formed during hot pressing, and the fine equiaxed Al2O3 and hexagon TiB2 particulates are formed simultaneously. On the other hand, there are fine Al3Ti precipitates in the composite fabricated from Al, B and TiO2 powders. After extrusion, the coarse Al3Ti blocks are broken into small pieces. Al2O3 particles are formed on the surface of TiO2 or B2O3 powder, TiB2 particles are formed on B or B2O3 powders, and they are fine and dispersively distributed. The formation of coarse Al3Ti block is resulted from long-distance diffusion of Ti in liquid Al.
Key words: hot pressing; Al matrix composite; Al2O3; TiB2; Al3Ti; microstructure
