Effect of Phase Fraction Ratio Between Al3Mg2 and Mg2Si on the Oxidation Behavior of Al–Mg–Si Alloys

Abstract

The effect of the phase fraction ratio between Al3Mg2 and Mg2Si on the oxidation resistance of Al–Mg–Si alloys at high temperatures was investigated. With addition of 1 mass%Si in Al-6 mass%Mg alloy, the as-cast microstructures showed formation of Mg2Si phase by eutectic reactions. With increasing Si content more than 3 mass%, the Mg2Si and Si are formed as eutectic phases with no β-Al3Mg2 phase. In addition, with an increase in the Si content from 3 mass%, significantly refined as-cast microstructures and distribution of extended eutectic phase areas were observed. The oxidized cross-sections of Al-6 mass%Mg and Al-6 mass%Mg-1 mass%Si alloys showed coarse and dark areas, which are considered as oxide clusters, nonuniformly grown into the matrix. However, Al-6 mass%Mg-3 mass%Si and Al-6 mass%Mg-5 mass%Si alloys had no significantly grown oxide clusters on the surfaces. Based on the results, it was concluded that the reduction of the ratio between β-Al3Mg2 and Mg2Si phases can reduce the rapid oxidation of Mg.