Effect of ball milling on simultaneous spark plasma synthesis and densification of TiC-TiB2 composites

The effect of ball milling pre-treatment of the starting Ti, B4C and C powders mixture on the synthesis of dense TiC/TiB2 composite was investigated through the combined use of a SPEX mill and the spark plasma sintering (SPS) apparatus. When unmilled reactants were used, amorphous carbon was converted to TiC through a combustion reaction with elemental titanium, while the complete conversion is achieved through a relatively slow reaction between the residual Ti and B4C. In contrast, powders ball milled for 24 It reacted completely under combustion regime. SPS product density was observed to increase from about 97% to 100% of the theoretical value, when the original powders were milled for 6 h, while further increase of the milling time led to a slight decrease in product density. Crystallite size of both boride and carbide phases decreased with milling down to about 50 nm after 24 It of mechanical treatment. The latter one also allowed for the formation of a material with relatively finer microstructure and more homogeneous phase distribution. (c) 2006 Elsevier B.V. All fights reserved.