Abstract:The evolution of microstructure in the oxidative growth of Al₂O₃/Al alloy composites was examined metallographically and analyzed by electron microprobe technique. The development of a nonprotective surface layer of MgO/MgAl₂O₄ allowed the continuous formation of an Al₂O₃-matrix composite containing an interpenetrating network of metal microchannels at 1 373 K. The role of Mg in the composite growth process was discussed by means of the lga_O2-Y_Mgphase diagram assuming that local equilibrium was established at the phase boundaries.

Key words: oxide layer　Al₂O₃/Al alloy composites　oxygen activity