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

摘要

A process has been invented for growing alumina (Al_2O_3) whiskers in the matrix of the aluminum-based metal matrix composite by the internal oxidation reaction between aluminum (Al) and molybdenum oxide (MoO_3) at 850 deg 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 l mu m in diameter and 10 mu m in length. The growth mechanism of the Al_2O_3 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 MoO_3 forming the Al_2O_3 whiskers and the Al-Mo intermetallic phases.