Morphology and growth mechanism of alumina whiskers in aluminum-based metal matrix composites

A process has been invented for growing alumina (Al₂O₃) whiskers in the matrix of the aluminum-based metal matrix composite by the internal oxidation reaction between aluminum (Al) and molybdenum oxide (MoO₃) at 850 °C. The whiskers were formed during the firing stage and distributed uniformly throughout the metal matrix. The fractional volume of the whiskers was about 30%, and their average size was 1 μm in diameter and 10 μm in length. The growth mechanism of the Al₂O₃ whiskers was studied. It was found that the nutrient for the growth of the whiskers was supplied from the molten Al at the base of the whiskers where they reacted with MoO₃ forming the Al₂O₃ whiskers and the Al–Mo intermetallic phases.