The effect of aluminum additives on the content and parameters of the fine structure of titanium carbosilicide in SHS powders

The dependence of the phase composition and parameters of the fine structure of titanium carbosilicide in powders obtained by the self-propagating high-temperature synthesis on the concentration of aluminum in the 5Ti/2SiC/1C reaction mixture was investigated. The aluminum concentration was varied in the range of 0.1–0.4 mole fraction while maintaining the total carbon content. It has been established that aluminum additives not only affect the yield of titanium carbosilicide, but also contribute to the predominant formation of Ti5Si3 instead of TiSi2 in synthesis products, which is identified in non-aluminum powders. The introduction of a small amount of aluminum (0.1 mole fraction) leads to the formation of a solid solution of Ti3Si1–xAlxC2 and reduces the content of impurity phases in SHS powders by 6 %. With a higher aluminum content in the reaction mixture, the concentration of carbosilicide in SHS powders decreases, and that of binary compounds (TiC, Ti5Si3, TiAl) increases accordingly. Within the concentration range of 0.1–0.25 mole fraction, no noticeable effect was observed from the introduction of aluminum on the crystal lattice parameters of titanium carbosilicide in SHS powders. A significant increase in the parameters a and c of Ti3Si1–xAlxC2 (from a = 3.067 Å, c = 17.67 Å to a = 3.07 Å, c = 17.73 Å) while maintaining the ratio with с/a within known values (с/a = 5.78) is observed only when the aluminum concentration is 0.4 mole fraction. The crystallite size of titanium carbosilicide depends primarily on the burning parameters. At the same time, the deformation of the Ti3Si1–xAlxC2 crystal lattice in SHS powders monotonically grows with increasing aluminum content in the reaction mixture in the investigated concentration range.