Thickness estimation (folds and wrinkles) on short time dynamically formed double oxide film in Al-7Si-Mg alloyed with beryllium

Abstract

In this study, the effect of beryllium additions on the morphology and thickness of the short time oxides formed on the Al-7Si-Mg alloyed with beryllium has been investigated. Estimations of the oxide films thickness showed that adding beryllium forms a flexible film with a thickness of about 30–100 nm on the alloy. The suitable locations for estimating the thicknesses of the double oxide films formed during dynamic conditions were introduced and explained. It is suggested that the procedure in which half width of the folds and wrinkles are reported as the film thickness, is not accurate technique because folds and wrinkles play significant roles in determining the minimum thickness of the dynamically formed oxide films. For this matter another method has been introduced. Moreover, by adding the beryllium, the thickness of some locations at the double oxide film middle layer is decreased which is a sign of bond improvement. Investigating the double oxide films using RPT tests showed that adding beryllium due to decreasing the thickness and increasing the flexibility of the oxide films, improve the bonding of the bifilm middle layer. Also, the thickness measurement of the alloy protected with the low and minor addition of beryllium showed that decrease in the bifilm thickness is a result of the beryllium surface protection and diffusion of this element into the oxide layer.