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 900° C 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 α-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.