Influence of laser surface treatment on the oxidation behaviour of an AlLiCu alloy

The environmental degradation behaviour of metals and alloys can be improved by modification of their surfaces using high energy beams. In the present work, an AlLiCu alloy of nominal composition 2.5% Li, 1% Cu and 0.12% Zr was laser treated with a Nd:YAG laser for the purpose of surface modification and its oxidation behaviour at 450°C in air was investigated by thermogravimetry. This was compared with the oxidation behaviour of a control (nonlaser-treated) specimen. Parabolic oxidation kinetics were observed for both the laser-treated and control specimens. The laser-treated specimen exhibited improved oxidation resistance. X-ray diffraction and scanning electron microscopy were used to characterize the oxide structure. X-ray diffraction analysis indicated that the major component of the scale was Li 2CO 3. The improved oxidation behaviour of the laser-treated specimen has been related to the compact oxide structure produced on its surface during oxidation. The nature of scale formation on the surface has also been addressed.