PHASE-RELATIONSHIPS IN THE TI-SI-C SYSTEM AT HIGH-PRESSURES

The compatibility of phases in the Ti-Si-C system was studied for pressures from 10 to 20 kbars (1 to 2 GPa) and temperatures from 1200-degrees-C to 1500-degrees-C via an interfacial reaction between titanium and silicon carbide. The interface was characterized by backscattered electron imaging and electron probe microanalysis. Ti3Si was stabilized at high pressures exhibiting an appreciable solubility for carbon (up to 9 at. %). At higher temperatures and lower pressures, it decomposed to Ti5Si3, Ti(Si, C), and TiCx according to the relation Ti3Si (C(z)) = (0.70588)TiCx + (0.32437)Ti5Si3 + (0.67227)Ti (Si, C), where the mathematical coefficients were calculated using z = 0.4 and x = 0.5. No detectable quantities of carbon dissolved in Ti5Si3 under these conditions. A clapeyron slope of 0.08 (+/-0.01) kbar/K was measured for this reaction. The microstructure of the reaction zone and other general thermodynamic and kinetic characteristics are discussed for different experimental conditions.