A transition from tetragonal monoclinic structure resulted as a consequence of the application of ball milling.The synthesis of the composite was carried out in the same way by applying mechanical ball milling in order to disperse 2 and 5 wt% of zirconium oxide particles into the Al alloy matrix. It was found that longertimeswere needed for the 5 wt% of Zro2 to achieve a complete dispersion into the matrix. unlike 2 wt% of zro2 sample, being 15 and 10 h, respectively. It was evident that the presence of zro2 particles had a marked influence upon the powder morphology and particle size of the matrix during the milling process. Despite the structural change observed, a relatively good homogenous dispersion ofzroz particles was foundafter ball milling.