Combustion synthesis and subsequent sintering of titanium-matrix composites

Titanium-matrix composites containing up to 50 wt% TiC particles were prepared by combustion synthesis using elemental powders. The products were subsequently sintered at 1160°C for various periods of time. SEM and X-ray diffraction were used to assess the changes that took place during the two stages of processing. Products of combustion synthesis containing in excess of 25%TiC contained large cracks as well as agglomerates of carbide particles that were undesirable from the point of view of reinforcing the metal. The carbide obtained by combustion synthesis had a higher carbon content than that expected according to the Ti-C equilibrium phase diagram, due to the non-equilibrium nature of the reaction. During the sintering stage, the carbide of non-equilibrium composition reacted with titanium to yield the carbide of equilibrium composition. The composition changes were investigated and their significance on the sintering process is discussed.