Oxidation behavior of a TiAl-Al2Ti4C2-TiC-Al2O3 in situ composite

A TiAl - Al2Ti4C2 - TiC - Al2O3 in situ composite was fabricated using TiO2, Al, and C as starting materials through a mechanical-milling and subsequently a pressureless-sintering process. Discontinuous and cyclic-oxidation tests were then carried out at 800 and 900degreesC in air up to 500 hr or 1000 cycles to evaluate its oxidation and oxide-scale-spallation resistance. The present results demonstrated that this composite had extremely high oxidation resistance in comparison with a Ti - 48Al - 2Cr alloy. The oxidation mass gains measured on the composite were about two orders of magnitude lower than that of the alloy. Moreover, the oxide on this composite showed superior spallation resistance; scale cracking or spalling could never be detected, while the alloy samples suffered severe scale cracking and spallation. Based on the morphological and cross-sectional observations, it is believed that alpha-Al2O3 and Al2Ti4C2 formed and incorporated in the composite could significantly influence the scaling behavior and then improve oxidation and spallation resistance of this composite.