Al_2O_3/TiAl复合材料的原位合成及反应机制的研究

Reaction Mechanism of In Situ Synthesized Al_2O_3/TiAl Composite

利用Al-Ti-TiO2体系的放热反应,原位合成了Al2O3/TiAl复合材料。借助示差热分析法探讨了体系的反应机制,采用XRD、SEM和OM分析了复合材料的相组成及显微组织。结果表明,原位合成Al2O3/TiAl复合材料由TiAl、Ti3Al和Al2O3相组成,Al2O3颗粒分布于TiAl和Ti3Al双相交界处,并存在一定团聚。随其含量增加,团聚程度加剧,晶粒尺寸减小。Ti和Al反应生成TiAl3放出的热量使部分TiAl3相处于液相状态,熔融的体积分数约为87.87%,液相的存在提高了颗粒间的润湿性,同时放出的热量是引发后续反应的原因之一。TiAl3与Al-TiO2的还原反应生成的活性Ti原子结合最终生成了TiAl和Ti3Al相。

Al2O3 particles reinforced TiAl matrix composite was in situ synthesized by use of the exothermic reaction of Al-Ti-TiO2 system. The reaction mechanism was investigated by differential thermal analysis （DTA）. The phases composition and microstructure of the composites was analyzed by XRD, SEM and OM. The results show that the product of the composite is composed of TiAl, Ti3Al and Al2O3. Al2O3 particles distributing in the intersection of TiAl and Ti3Al matrix, and are slightly aggregate. With increasing the Al2O3 content, the agglomeration phenomenon increases, but the grain size decreases. Heat released by reaction of 3Ti ＋ Al（L）→TiAl3 makes partial TiAl3 melt into liquid whose volume fraction is 87.87 %. The liquid phase improves the wettability of particulates and the heat release induces the subsequent reactions. Finally, TiAl3 reacts with active Ti atoms formed by Al-TiO2 reducing reaction, producing the ultimate phases, TiAl and Ti3Al.