Intermetallic compounds have been the focus of significant research and development efforts during the last 15 years. The promise of very strong tough structural materials at elevated temperatures has tantalized researchers for several decades. The technological attraction comes mainly from new aerospace needs for high temperature structural materials with properties that cannot be met by ceramics or by conventional superalloys. Intermetallic CoTi has received a great deal of attention as candidate materials for high-temperature applications because of its low density, high specific strength, good oxidation and corrosion resistance at elevated temperatures. Several techniques such as self propagating high temperature synthesis (SHS), reactive hot press and mechanical alloying (MA) have also been developed to produce a wide array of intermetallic matrix omposites. Among these methods, MA technique is well known for synthesis of compounds and nanocomposites using the mechanochemical reactions. MA is a technique to roduce powders with unique microstructures, such as nanoscale structures and morphous phases. Its attraction is that it has a near-net-shape product, which can greatly reduce the shaping process. Therefore, Mechanical alloying method was used in this research to study the formation and properties of CoTi nanocomposite reinforced by TiC particles. Ball milling process was performed in two stages; first, producing the nano-structured CoTi intermetallic and second formation of TiC reinforcement in CoTi matrix followed by in-situ production of CoTi-TiC nanocomposite. Mechanical alloying of pure cobalt, titanium and carbon powders with stoichiometric ratio and Ball-to-Powder Weight Ratio of 10:1 and 5:1 was carried out using a high energy ball mill with speed of 300 rpm in various time intervals. Heat treatment process was carried out in vacuum furnace at 900 °C for 30 and 60 min. Transition and scanning electron microscopes and X-ray diffraction technique were employed to examine the microstructural evolution. In addition, crystallite size and lattice distortion changes in the powder mixtures were investigated using the sigma plot software and Williamson-Hall method at different stages. The results showed that an increase in Ball-to-Powder Weight Ratio from 5:1 to 10:1 lead to a decrease in production time of CoTi from 20 to 8 hours, a decrease in grain size and a considerable increase in internal strain and hardness in the final specimens. The CoTi phase obtained had a particle size of about 10 µm, crystallite size of 14 nm and lattice distortion of 0.5%. The CoTi-TiC nanocomposite represented a particle size of about 15 µm, crystallite size of 15 nm and lattice distortion of 1.5%. In all specimens, increase in ball milling time was associated with an increase in hardness and lattice distortion and a decrease in crystallite size of powder mixtures. The hardness of CoTi was
