Changes inγ-TiC stoichiometry during heat treatment of TiC reinforced Ti composites

A liquid phase technique (casting) has been successfully employed for the production of Ti/TiC in situ metal matrix composites. The γ-TiC phase produced by this process is highly substoichiometric. Changes in chemistry of the TiC phase in these composites are noted during annealing at elevated temperatures. The degree of stoichiometry of TiC increases during annealing at 1050°C and further during post-annealing aging at 750°C. This increase in the degree of stoichiometry (C/Ti atomic ratio) is accompanied by lattice expansion and reduction in microhardness values of the TiC particles. The change in TiC stoichiometry is accompanied by the precipitation of soft Ti particles within the TiC phase. The results are compared with those obtained from composites fabricated by a powder metallurgy route where the carbide chemistry is insensitive to heat treatment.