Synthesis of an Al2O3/Al co-continuous composite by reactive melt infiltration

The route for the fabrication of an Al2O3/Al co-continuous composite by reactive melt infiltration was investigated using scanning electron microscopy, energy dispersive X-ray microanalysis and X-ray diffraction analysis. It was found that in the process of molten aluminium infiltration into the SiO2 preform, the chemical reaction of 3SiO2 + 4Al → 2Al2O3 + 3Si occurred at the infiltration front, and generated a transition zone containing a new type of continuous porosity about 100 μm in width. The reaction continued with further infiltration of molten aluminium alloy into this porosity which reacted with the residual SiO2 until all the SiO2 was transformed into Al2O3. A comparison was made between this route and that by direct infiltration of molten aluminium alloy into the open porosity of an Al2O3 preform. As a result of the increased wetting ability of the molten aluminium alloy by the chemical reaction, reactive melt infiltration took place at a higher rate for the SiO2 preform than that for the direct infiltration of the Al2O3 preform. A fracture surface examination demonstrated a toughening effect provided by the continuous aluminium alloy in the composite.