Abstract: Two metal matrix composites(MMCs),Saffil/Al-5.5Mg and Saffil/Al-5.5Zn were manufactured with the squeeze cast technique. The volume fraction of fibres was 10%,15% and 20% respectively. Optical microscopy analysis indicated that fibres appeared to be two-dimensional randomly oriented. The values of ultimate tensile strength CUTS) of matrix and MMCs were measured at room temperature and 300 C.The fracture surfaces were investigated by the scanning electron microscopy. The fracture mechanism and the reasonable formulae for the prediction of strength under various conditions were analysed and discussed.