采用自蔓延高温合成技术连接TiAl合金

采用自蔓延高温合成技术实现了TiAl合金的连接。在连接过程中采用了具有很高放热量的Ti-Al-C中间层以及外加电磁场辅助连接。连接接头包括3个典型的反应区域，靠近TiAl母材界面处发现了深灰色的TiAl，反应层，在中间层内观察到了TiC颗粒以及Ti-Al系化合物。直接连接时由于产物和反应物之间的比热差，杂质的气化和孔隙中束缚气体的释放而导致孔隙无法避免。为了提高致密度，在粉末压坯和TiAl母材之间添加了Ag-Cu钎料箔。在SHS反应过程中熔化的钎料改善了中间层对TiAl母材的润湿同时填充到了中间层反应产物的孔隙中，采用这种方法能够提高反应产物的致密度和连接质量。

Joining of TiAl intermetallic by self-propagating high-temperature synthesis

A novel approach for joining TiAl by self-propagating high-temperature synthesis (SHS) was studied in the study. The Ti, Al and C powders with large exothermic enthalpy and the assisted electromagnetic field were applied in the joining processing. The typical joint was composed of three reaction zones. Adjacent to the TiAl base metal, a dark TiAl3 reaction layer was observed on the interface. The TiC particles and Ti-Al compounds were found in the interlayer. It was also noted that in every condition the porosity could not be avoid due to the differences in specific volume between products and reactants, the evaporation of impurities, and the expansion of the gas trapped in the porosity of the reactant compact. In order to solve these problem, Ag-Cu brazing foils were placed between the powder compacts and the TiAl substrate. It was considered that molten Ag-Cu in the filler during SHS reaction improved the wettability of interlayer to TiAl substrate and filled well into the holes in the reaction products of the interlayer. In this way, the density could be increased and the joint quality could be improved.