Changes in gamma-TiC stoichiometry during heat treatment of TiC reinforcedTi composites

A liquid phase technique (casting) has been successfully employed for the p roduction of Ti/TiC in situ metal matrix composites. The gamma-TiC phase pr oduced by this process is highly substoichiometric. Changes in chemistry of the TiC phase in these composites are noted during annealing at elevated t emperatures. The degree of stoichiometry of TiC increases during annealing at 1050 degrees C and further during post-annealing aging at 750 degrees C. This increase in the degree of stoichiometry (C/Ti atomic ratio) is accomp anied by lattice expansion and reduction in microhardness values of the TiC particles. The change in TiC stoichiometry is accompanied by the precipita tion of soft Ti particles within the TiC phase. The results are compared wi th those obtained from composites fabricated by a powder metallurgy route w here the carbide chemistry is insensitive to heat treatment. MST/4346.