Formation of Al2O3/Metal Composites by the Directed Oxidation of Molten Aluminum-Magnesium-Silicon Alloys: Part II, Growth Kinetics

Authors


  • C. A. Handwerker—contributing editor

  • Supported in part by the Defense Advanced Research Projects Agency and Office of Naval Research under Contract No. N00014–85–C-0015.

  • Technology patented by Lanxide Corporation and included under the Tradename DIMOXTM directed metal oxidation technology.

Abstract

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.

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