自生TiC增强钛基复合材料的微观组织

采用反应自生法制备了ＴｉＣ颗粒增强钛合金基复合材料，研究了复合材料的相组成和微观组织。在Ｔｉ－６Ａｌ－２Ｃ合金中存在Ｔｉ和ＴｉＣ两种相。ＴｉＣ权树枝状初生Ｔｉｃ和短棒状共晶ＴｉＣ两种开头存在，其中共晶ＴｉＣ主要存在于晶界，特别是三角晶界处。ＴｉＣ晶格常数的计算结果表明ＴｉＣ的衍射峰存在一定的偏移，主要是由于存在于ＴｉＣ中的Ｃ空位引起晶格畸变。随着Ａｌ含量的增加，初生ＴｉＣ由发达粗大的树枝晶变为不发达的树枝晶，当Ａｌ含量为３５％时变为短棒状和薄片状的ＴｉＣ。基体组织也相应地由单一的Ｔｉ基体变为Ｔｉ和Ｔｉ３Ａｌ的两相基体以及Ｔｉ３Ａｌ和ＴｉＡｌ两相基体。根据相图分析了组织变化的主要原因。

MICROSTRUCTURE OF IN SITU TiC REINFORCED TITANIUM ALLOY MATRIX COMPOSITES

TiC particulate titanium alloy matrix composites with different Al content has been prepared by a reaction synthesis method. The phase constitution and the microstructure of the composites have been investigated in detail by XRD, SEM. The results showed that the Ti--6Al--2C is composed of Ti and TiC reinforcements. TiC is composed of two different morphologies: coarse developed dendritical primary TiC and short bar--shape eutectic TiC, and the eutectic TiC mainly distributes at the grain boundary, especially at the triple--point grain boundary. The calculated result of the lattice of TiC from XRD pattern showed that there exists TiC diffraction peak shift which may be due to the vacancies of C in TiC structure. The effect of Al content on the microstructure and the morphology of TiC has also been studied. It has been shown that with the increasing of Al content the morphology of primary TiC changes from coarse developed dendrite to undeveloped dendrite, up to short bar--shape or plate--shape TiC at 35% Al. Meanwhile, the microstructure of the matrix changes from single Ti to Ti and Ti3Al, and to Ti3Al and TiAl at 35% Al. The reason has been discussed.