Synthesis of an Al 2O 3/Al co-continuous composite by reactive melt infiltration

Abstract

The route for the fabrication of an Al 2O 3/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 SiO 2 preform, the chemical reaction of 3SiO 2 + 4Al → 2Al 2O 3 + 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 SiO 2 until all the SiO 2 was transformed into Al 2O 3. A comparison was made between this route and that by direct infiltration of molten aluminium alloy into the open porosity of an Al 2O 3 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 SiO 2 preform than that for the direct infiltration of the Al 2O 3 preform. A fracture surface examination demonstrated a toughening effect provided by the continuous aluminium alloy in the composite.