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 degrees 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 Li2CO3. 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. (C) 1997 Elsevier Science S.A.