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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。
In-situ (Al2O3 + TiB2 + Al3Ti) / Al composites were prepared by thermal pressing of B or B2O3, TiO2 and Al powders. The microstructures of in-situ composites were analyzed by optical microscope, scanning electron microscope and transmission electron microscope. Under hot pressing condition, the Al3Ti phase was irregular in shape and the size was about tens of micrometers. Al2O3 and TiB2 were fine dispersed particles. TEM analysis showed that the TiB2 particles were hexagonal while the Al2O3 particles were equiaxed. In the composites prepared by using Al powder, TiO2 powder and B powder as raw materials, in addition to the bulk Al3Ti phase formed by the reaction, fine acicular Al3Ti phase precipitates and disperses. After the hot extrusion bulk Al3Ti was broken into small diffuse particles. Al2O3 is formed on the surface of TiO2 and B2O3 powders; TiB2 is formed on the surface of B or B2O3 powders, which are dispersed and small in size. When Ti reduced from TiO2 is dissolved in liquid Al to form Al3Ti, Ti can diffuse over a long distance in liquid Al, so Al3Ti is irregular in shape.