Oxidation Behavior of Nanocrystalline Al Alloys Containing 5 and 10 at.% Ti

The oxidation behavior of mechanically alloyed(MA) Al-Ti alloys containing 5 and 10 at.% Ti wereinvestigated at 500-600°C under 1 atm of oxygen. Ateach temperature, alloys oxidized linearly during the initial stage and later followed the parabolicrate law. During the initial stage, the oxidation ratesof nanocrystalline (50 nm) Al-Ti alloys were fasterthan those of conventional (200 nm) alloys. It is suggested that more grain boundaries innanocrystalline alloys provide more nucleation sites foroxides, so that the oxide scales grew faster as denseprotective layers. During the parabolic stage, the nanocrystalline alloys had greater oxidationresistance than conventional alloys because of the denseprotective layer. Oxide scales on both alloys consistedof a mixture of -Al₂O₃ andTiO₂ in the outer layer and-Al₂O₃ near the alloy as aprotective layer.