• oxidation;
  • alumina;
  • aluminum;
  • alloys;
  • kinetics

The growth kinetics of an Al2O3/metal composite by the directed oxidation of an aluminum alloy (10 wt% Si, 3 wt% Mg, balance Al) have been measured as a function of temperature (1398 to 1548 K) and oxygen partial pressure in O2/Ar gas mixtures. The growth rate exhibited an activation energy of ∼370 kJ/mol and a dependence on oxygen partial pressure consistent with a Po1/42 relationship. A dissolution-precipitation growth mechanism is proposed in which the growth rate is controlled by the electronic conductivity of an external Al2O3-doped MgO surface layer in conjunction with grain boundary diffusion of magnesium.