Oxidation Behaviors of In-situ Synthesized TiC/Ti-6Al Metal Matrix Composite at High Temperatures

摘要

Oxidation behavior of in-situ synthesized 10 vol.% TiC/Ti-6Al metal matrix composite was studied by using TGA at 600°C, 700°C and 800°C for 20 hours, respectively. The experimental results show that oxidation of in-situ TiC/Ti-6Al at high temperatures basically follows a parabolic law. The activation energy for oxidation is calculated to be 255.7 kJ/mol. The weight gain when oxidized at 800°C is much higher than that at 600°C and 700°C. And the oxidation products at 800°C contain rutile TiO2 and α-Al2O3,,while the oxides are mainly TiO2 when oxidized at 600°C and 700°C. The microstructures of oxides reveal that the oxide scales when oxidized at 800°C formed an integrated film on the surface of sample, however, for the cases oxidized at 600°C and 700°C the oxides were un-continuous and island-like. The formation of oxidation islands at 600°C and 700°C was contributed to the higher reactivity of TiC and oxygen than that of Ti and oxygen. A non-homogeneous oxidation mechanism in the composite due to the prior oxidation of TiC was firstly observed, which is quite different from Ti alloys.