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.