Oxidation of Al-Mg alloys in small scale experiments

Abstract

While a significant amount of work has been done on the oxidation of Al-Mg alloys a limited portion of the work has been done under a true furnace atmosphere created by an air-fuel or oxyfuel burner. A series of oxidation tests were carried out in Lindes's test furnace using an air-fuel burner. Al samples weighing approximately 65 grams with between 0 and 5 % Mg were placed in a steel crucible and further placed in an air-fuel fired box furnace for 0.16, 0.5, 1, 2, 3 or 5 hours before being removed to cool. The samples were analysed afterwards by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Analysis showed that all samples had a MgAl2O4 layer on the surface and that at higher Mg contents internal oxidation occurred resulting in the formation of MgO or MgAl2O4 clusters in the melt. This would indicate that under the oxidation conditions in an air fired furnace a significant portion of the oxidation may occur inside the melt leading to an increase in oxide inclusions.