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.
Microstructure formation mechanism of (Al2O3+TiB2+Al3Ti) /Al composites fabricated by reaction hot pressing
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.
图2 反应热压制备的两种 (Al2O3+ TiB2+Al3Ti) /Al基复合材料的XRD谱 Fig.2 XRD patterns of in-situ (Al2O3+ TiB2+Al3Ti) /Al composites made from different raw materials (a) —Al+B2O3+TiO2; (b) —Al+B+TiO2
图3 采用Al+B2O3+TiO2体系制备的 (Al2O3+TiB2+Al3Ti) /Al原位复合材料的显微组织 Fig.3 Microstructures of in-situ (Al2O3+TiB2+Al3Ti) /Al composite made from Al+B2O3+TiO2 system (a) —OM image after hot pressing; (b) —OM image after hot extrusion; (c) —TEM image after hot extrusion
图4 采用Al+B+TiO2体系制备的 (Al2O3+TiB2+Al3Ti) Al原位复合材料的显微组织 Fig.4 Microstructures of in-situ (Al2O3+TiB2+Al3Ti) Al composite made from Al+B2O3+TiO2 system (a) —OM image after hot pressing; (b) —SEM image after hot extrusion; (c) —TEM image after hot extrusion
图5 (Al2O3+TiB2+Al3Ti) /Al复合材料显微组织形成机制示意图 Fig.5 Schematic illustration of formation mechanism for in-situ (Al2O3+TiB2+Al3Ti) /Al composite