Effects of TiC and Al4C3 addition on combustion synthesis of Ti2AlC

Abstract

Preparation of the ternary carbide Ti 2 AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from the elemental powder compacts of Ti:Al:C = 2:1:1, TiC-containing samples with TiC of 6.67–14.3 mol%, and Al 4 C 3 -containing samples with Al 4 C 3 of 1.96–10 mol%. Effects of TiC and Al 4 C 3 addition were studied on combustion characteristics and the degree of phase conversion. Due to the growth of laminated Ti 2 AlC grains, the reactant compact was subjected to an axial elongation during the SHS process. Because the addition of TiC and Al 4 C 3 led to a decrease in the reaction temperature, the flame-front propagation velocity was correspondingly reduced for the TiC- and Al 4 C 3 -containing samples when compared with the elemental reactants. Based upon the XRD analysis, formation of Ti 2 AlC along with a secondary phase TiC was identified in the synthesized products. The grains of Ti 2 AlC are typically plate-like with a size of 10–20 μm and several laminated Ti 2 AlC grains form a layered structure. The content of Ti 2 AlC yielded from the elemental powder compacts is about 85 wt%. The addition of TiC was found to facilitate the formation mechanism and therefore to enhance the extent of Ti 2 AlC conversion approaching 90 wt%. As a result of the reduced exothermicity of the reaction, however, the content of Ti 2 AlC decreased slightly in the products synthesized from the Al 4 C 3 -added samples.