Effects of 2 ppm Beryllium on the Oxidation of a 5XXX Aluminum Alloy at Temperatures Between 500 and 750 °C

The oxidation of molten aluminum has been thoroughly studied, and it is established empirically that beryllium has an inhibiting effect on the oxidation behavior. The aim of this work was to increase the fundamental understanding of this inhibiting effect. Two 5XXX aluminum alloys (4.7% Mg), one with 2 ppm of beryllium and one without beryllium, were oxidized in a tube furnace under a dry air atmosphere. Samples were oxidized at temperatures from 500 to 750 °C for 10, 30 and 120 min. The composition and morphology of the oxide layers were examined with FIB and EDS, revealing the differences between the samples. The results showed up to a tenfold reduction in mass gain in samples containing beryllium. Significant differences in the oxide layer morphology were found for the two alloys at all times, including from 10 min. Thus, beryllium plays a significant role from the onset of high temperature oxidation.