Oxidation behaviour of molten magnesium and AZ91D magnesium alloy in 1,1,1,2-tetrafluoroethane/air atmospheres

The oxidation rates, the morphologies and compositions of the surface films on molten magnesium and AZ91D alloy in covering gas of 1,1,1,2-tetrafluoroethane/air at 760 degrees C were investigated using thermogravimetric techniques, SEM, XRD and XPS. The oxidation rates of the two melts followed parabolic law in the atmosphere of high concentrate 1,1,1,2-tetrafluoroethane, and obeyed linear law in the atmosphere of low concentrate 1,1, 1,2-tetrafluoroethane. But the oxidation rates of molten magnesium and AZ91D alloy presented a certain difference. The oxidation products on its surface films were composed of MgF2 which played an import role to prevent the molten oxidation and other compounds. (c) 2008 Elsevier Ltd. All rights reserved.