Investigation of Oxide Film Characteristics in Al-Zn Melt by Oxide-Metal-Oxide Technique

The oxide/metal/oxide sandwich method is one of the techniques for investigating the dynamic oxidation of the melt. For preparation of the oxide/metal/oxide sandwich samples air bubbles, with 0.8-atmosphere pressure, were blown into the melts and the intersection of the entrapped bubbles was taken for the study. The characteristics of surface oxide films in different amounts of zinc (3, 5, and 7 weight percent), including their morphology and thickness, were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). There was no significant difference in the morphology of oxide films in the investigated alloys. However, in higher Zn content, more cracks and locations of stress concentration were found on the oxide film. The thickness of the oxide films of Al-Zn alloys were estimated between 95 to 1070 nm. By adding zinc up to 3% wt., the thickness of the oxide film is increased while adding more than 3% zinc causes decrement in the thickness of the film. Reducing the thickness of oxide films is possibly an indication of the increase in oxidation resistance of the Al-Zn alloys