Effect of Sc on the Oxidation Behavior of Al-2Li Alloys in the Molten State

The impact of Sc on the oxidation behavior of molten Al-2Li alloys was investigated across a temperature range of 640–840°C. It changed the overall weight gain of the alloy from a decreasing trend with increasing temperature to an increasing trend with increasing temperature throughout the oxidation process. The primary reason is that incorporating rare earth elements alters the oxide film’s mass transfer mechanism, exerting control over the oxidation process through the inward diffusion of anions. Adding Sc enhances the oxide film’s density and integrity on the alloy’s surface, rendering the substrate less susceptible to oxidative attack below 740°C. Nevertheless, this leads to the formation of Li₅AlO₄, resulting in an oxidized weight gain above 790°C that exceeds the oxidized weight gain of Al-2Li. Furthermore, tensile stresses are imposed on the oxide film in the vicinity of the gas/oxide film interface, thereby enhancing the susceptibility of the surface oxide layer to flaking.