AIR OXIDATION BEHAVIOR OF TI-6AL-4V ALLOY BETWEEN 650-DEGREES-C AND 850-DEGREES-C

The air oxidation behaviour of Ti-6Al-4V alloy was studied in the temp erature range 650-850 degrees C. Continuous oxidation kinetics showed that the alloy oxidised according to a parabolic rate law at 650 and 7 00 degrees C after a transient period, whilst at 750 and 800 degrees C , linear-parabolic kinetics dominated. At 850 degrees C, after 50 h li near-parabolic oxidation, the alloy followed a parabolic rate law. The multilayered oxide scales formed on the oxidised alloy consisted of a lternate layers of Al2O3 and TiO2. The number of Al2O3 and TiO2 layers increased with increasing exposure time and temperature. The external gas/oxide interface was always occupied by an Al2O3 layer whilst TiO2 always appeared at the oxide/substrate interface.