Effect of short-time thermal oxidation on the surface of Al−Li−Cu−Mg alloy (8090) sheet

Abstract

The oxidation behaviour of 8090 Al−Li alloy sheet was studied after exposure for short times (<5 min) in laboratory air, moist air, moist argon and hydrogen at 530°C. Oxidation was greater at grain boundaries in hydrogen but not in air. Sites of rapid local oxidation (number density 9 to 8 × 10³ cm⁻²) were associated with insoluble particles. Four types of growth morphology were identified with these sites. Some growths believed to be spinel, were 10 to 25 μm diameter and grew to ≈1 mm in height at 2μm sec⁻¹. Pits beneath these growths were ≈25 μm diameter and 10 to 20 μm deep. A qualitative model is proposed for rapid oxidation in Al−Li alloys and the effect of these sites on weight gain measurements, surface contamination and mechanical properties is discussed.