FORMATION OF COMPOSITE MATERIAL OF METAL/TWO-PHASE CERAMIC WITH VAGUE INTERFACE BY IN SITU OXIDATION OF MOLTEN ALUMINUM ALLOY

A novel technique by using graphite immersed by K₂CO₃ solution to cover with the surface of molten alloy and setting porous ceramics in advance to transport atmosphere, is realized to in situ oxygenize molten alloy from its surface into its interior. The attractive features of the new technology in comparison with conventional growth technology are densified reaction resultant, smooth macro-surface around samples, and samples of front without rugged cellular stacking on them. It is found by microstructure observation, X-radial diffraction analysis(XRD) and by electron probe X-ray microanalysis(EPMA) that oxides grow in the form of columnar crystal consisting of clumps or grains of micron oxides in whichα-alumina is the main and silica a little, with continuous ingredient variation between two phases and clumps or grains, showing a tendency ofα-alumina wrapping silica without distinct surfaces between them, and having the strong character of directional growth; and alloy phases mainly distribute in the interface of columnar crystal corps.