Microstructure and High Temperature Oxidation Resistance of TiC/Ti-25Al Composites

With the reaction between titanium (Ti) sponge, high purity aluminum (Al) and TiC/Al inter-alloy, non-consumable arc melting technique has been successfully used in situ synthesize Ti matrix composites of Ti-25Al and Ti-25Al-1.5C. The composites oxidized at 900°C for 5~60h in static air. The influences of carbon content to oxidation kinetics of composites were analyzed. The surface morphologies and cross-section microstructures of the oxidation scales were examined by scanning electron microscope (SEM) with energy dispersive spectrometer (EDS). The results show that the isothermal oxidation kinetic curves of composites mainly follow parabolic rate law. The surface oxides of two materials are mainly columnar TiO2, while the grain size of Ti-25Al-1.5C is smaller than that of Ti-25Al. The cross-section microstructure of the oxidation scales of Ti-25Al are layered constructions which grow in alternating way. The oxides of Ti-25Al-1.5C are mainly around the carbide particles, the oxidation resistance of which is stronger than Ti-25Al when oxidized for long time.