Oxide film characteristics of AZ91 magnesium alloy in casting conditions

Abstract

Molten magnesium alloys oxidise rapidly during casting and handling if adequate prevention measures are not taken. New oxide films that form in a very short time during pouring seem to be one of the main reasons for dross-like defects. The characteristics of these new oxide films were observed. The magnesium alloy AZ91 was selected for the study. Samples were prepared based on the technique in which an oxide-metal-oxide sandwich was made by bubble impingement. After impingement the contact areas of two adjacent and entrapped bubbles were selected for the study. Features such as thickness, size, morphology and chemical composition of the oxide film have been examined and shown by SEM. Possible consequences of the morphology of the oxide film were discussed.