Static and cyclic oxidation of Ti-44Al and Ti-44Al-xNb alloys

Binary Ti-44Al, and ternary, Ti-44Al-xNb (x = 4, 8, and 11) alloys were sub jected to static and cyclic oxidation in air up to a period of 1 week at 85 0 and 950 degreesC, The oxidation behavior is characterized by plotting a g raph between,weight gain us a function of time or number of cycles. The bin ary alloy undergoes tire most severe oxidation while Nb provides resistance to oxidation, which increases with an increase in concentration. Oxides we re examined by SEM and EDX was used to perform chemical analysis. Alternate oxide layers rich in alumina and titania were found along with an aluminum -depleted zone underneath the oxide scale. Different microstructures were o bserved for the alloys subjected to static- and cyclic-heating modes. Defec ts like twins and stacking faults were generated after a static mode of hea ting, while transformation products at the grain boundaries dominate the mi crostructures for samples subjected to cyclic heating.