Effects of TiC, TiH2, Al, and Carbon on Production of Ti3AlC2 by Self-Sustaining Combustion Synthesis

Abstract

The production of Ti3AlC2 was investigated by self-propagating high-temperature synthesis (SHS) using the sample compacts composed of elemental powders with or without TiC and TiH2 additions. The influence of Al, carbon, TiC, and TiH2 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 Ti3AlC2, but the sample with a carbon-deficient composition produced the opposite effect. Although both TiC and TiH2 additions decreased combustion exothermicity, an appropriate amount of TiC enhanced the yield of Ti3AlC2. However, the incomplete decomposition made TiH2 unsuitable as a source of Ti and resulted in a low yield of Ti3AlC2. In this study, the final product containing the highest content of Ti3AlC2 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.% Ti3AlC2, 5.9 wt.% Ti2AlC, and 4.8 wt.% TiC. A reaction mechanism was proposed for the formation of Ti3AlC2 by SHS, which involved three exothermic reaction steps sequentially producing TiC, Ti2AlC, and Ti3AlC2. The as-synthesized Ti3AlC2 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.