Microstructures directed metal oxidation

Fig. 5. The microstructure of zirconium diboride-reinforced zirconium carbide composites produced by directed metal oxidation, (a) A composite prepared with 22 vol % metal, (b) A composite produced with less than 2 vol % metal. 

The microstructures of ceramic matrices grown from two different classes of alloys have been reported. The external growth surface of ceramic matrices grown from an Al-Si-Mg alloy in the absence of a reinforcement was covered by a thin ( 1- to 4-gm) layer of MgO that sometimes contained up to 5% MgAl204 [33]. The external MgO layer typically was separated from the interconnected A1203 matrix by a thin aluminum alloy (1- to 3-gm) layer. Only rarely was an A1203 grain found in direct contact with the external oxide layer. Within the bulk of the composite, the metallic channels typically were 3 to 8 /tm in width. 

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