showed that the major strengthening mechanism in aluminum matrix composites reinforced Al203 is the orowan strengthening by particles; however, he found that when clusters of these ceramic particles were present, the particle strengthening effect diminished. This is the reason why the parameters ofthe MM process need to be studied and optimized in order to obtain a fine dispersion of partially yttria-stabilized zirconia through the AA 7075 matrix by using mechan- ical ball milling and to characterize its microstructural evolution through the process.