Oxidation Behavior and Oxide Layers of Ti–50Al Intermetallics by Preoxidation in High-Pressure Oxygen

The oxidation resistance of Ti–50Al intermetallics is improved bypreoxidation for 1, 4, or 16 hours in high-pressure, pure oxygen(≈3.9 atm) at 900°C. Specimens preoxidized for 1 hr exhibit betteroxidation resistance than others. Prolonged preoxidation time candeteriorate the oxidation resistance and reduce the parabolic-lineartransition time during subsequent cyclic oxidation in 800°C air. Theoxide-mound occurrence is an important factor for evaluating theeffectiveness of the preoxidation treatment in oxygen. The formationmechanism of Z-phase (Ti5Al3O2) in the Al-depleted layer beneath theflat oxide scale and that beneath the oxide mound are also proposed inthis study.