XPS studies of oxide growth and segregation in aluminium-silicon alloys

The oxidation of three aluminium-silicon alloys has been studied as a function of temperature. At temperatures below 473 K a thin passivating oxide film is formed. At higher temperatures the segregation of the trace element magnesium to the surface is observed where it dominates the subsequent oxidation behaviour. In the absence of oxygen, magnesium segregation does not occur. From these results it is concluded that at temperatures in excess of 473 It magnesium segregation controls oxide growth and also that the degree of segregation is temperature dependent. Segregation effects are also observed for sodium, which appears to be concentration limited, and silicon, which is confined to the alumina-rich regions close to the metal surface where the silicon is also oxidized. (C) 1997 by John Wiley & Sons, Ltd