INFLUENCE OF LASER-SURFACE TREATMENT ON THE OXIDATION BEHAVIOR OF AN AL-LI-CU ALLOY

The environmental degradation behaviour of metals and alloys can be im proved by modification of their surfaces using high energy beams. In t he 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 i n air was investigated by thermogravimetry. This was compared with the oxidation behaviour of a control (nonlaser-treated) specimen. Parabol ic oxidation kinetics were observed for both the laser-treated and con trol specimens. The laser-treated specimen exhibited improved oxidatio n resistance. X-ray diffraction and scanning electron microscopy were used to characterize the oxide structure. X-ray diffraction analysis i ndicated that the major component of the scale was Li2CO3. The improve d oxidation behaviour of the laser-treated specimen has been related t o 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.