Effects of TiC, TiH, Al, and Carbon on Production of TiAlC by Self-Sustaining Combustion Synthesis.

The production of TiAlC was investigated by self-propagating high-temperature synthesis (SHS) using the sample compacts composed of elemental powders with or without TiC and TiH additions. The influence of Al, carbon, TiC, and TiH was explored on the combustion sustainability, combustion velocity and temperature, and phase composition and microstructure of the product. The experimental results indicated that the elemental sample with an Al-excess composition increased the combustion velocity and improved the formation of TiAlC, but the sample with a carbon-deficient composition produced the opposite effect. Although both TiC and TiH additions decreased combustion exothermicity, an appropriate amount of TiC enhanced the yield of TiAlC. However, the incomplete decomposition made TiH unsuitable as a source of Ti and resulted in a low yield of TiAlC. In this study, the final product containing the highest content of TiAlC was synthesized from the Al-excess and TiC-added sample of 2.5Ti + 1.2Al + 1.5C + 0.5TiC, and the product was composed of 89.3 wt.% TiAlC, 5.9 wt.% TiAlC, and 4.8 wt.% TiC. A reaction mechanism was proposed for the formation of TiAlC by SHS, which involved three exothermic reaction steps sequentially producing TiC, TiAlC, and TiAlC. The as-synthesized TiAlC grains were in the shape of thin platelets with a thickness of about 1.0 μm, and a layered structure formed by closely stacked platelets was clearly observed.