Analysis of combustion synthesis process of TiAl intermetallic compound by dipping experiment of Ti wire into Al melt

The combustion synthesis process has attracted attention as new synthesizing technology of intermetallic compounds. However, as the products tend to be porous and the process control condition is not clear, the process has not been put in practical use. To realize the production of intermetallic compounds by combustion synthesis process, fundamental mechanism or compound formation stages in the combustion reaction should be made clear. In this paper, the compound formation behavior between the Ti and the Al melt was measured, and the compound formation stages in the combustion synthesis of TiAl was investigated. Dipping experiment which dipped a Ti wire into the Al melt was performed under various conditions of the holding time and temperature. On the other hand, the Ti/Al mixed compacts were quenched during the thermal explosion reaction. The compound formation stage of TiAl was estimated by comparison between the cross section of dipped wires and the microstructure of quenched compacts. By the dipping experiment, it was found that the compound formation behavior in the Ti-Al system changed with temperature. At the low temperature such as 973 similar to 1173 K, the formation reaction of TiAl3 took place, and small dispersive particles were formed around a Ti wire. However, in the dipping at high temperature as 1373 It or 1473 K, the Ti(alpha, beta) solid solution formed in the mire. In a quenched compact, these phases were detected as well. The TiAl3 phase was found in a compact quenched at the initial stage of synthesis, and the Ti(alpha, beta) solid solution phase was observed at the middle stage. Therefore, it was estimated that the compound formation in the TiAl combustion synthesis progressed through the formation of these phases. As the synthesis reaction was affected by the combustion temperature, the temperature control is of importance to improve the microstructure and synthesized phase of the product.