In recent years magnesium matrix composites, due to their low density and high specific strength are used extensively in automobile and space industry. One of the advanced routes for manufacturing the magnesium-matrix composites is infiltration casting into ceramic foams. In this research, magnesium-matrix composite AZ91-Al 2 O 3 production has been investigated. Therefore, AZ91 alloy molten is prepared by usage of torch furnace under protection of MAGREX flux, then, poured in preheated mould at 250°C with preheated alumina foam at 800°C. For investigating the casting temperature on the microstructure and mechanical properties, melting temperature was set at 700-790°C, and then, pressures at 50, 75 and 100 MPa in 1 minute applied until solidification was completed. For comparison, similar experiments were done without applying pressure. The results showed that solidification under pressure reduced porosity noticeably in comparison with gravity casting to 60%. By addition the ceramic reinforcement to the base alloy, mechanical strength reduced due to formation of MgAl 2 O 4 spinel phase at interface and formation of residual compression stresses because of thermal mismatch between matrix and reinforcement. When experimental temperature is increased (300°C), due to enlarging of grain size and alloy flowing, the strength of base alloy decreased to 20% of strength at room temperature. Although, the ductility is not increased sharply (23%). Also, because of relaxation of residual stresses, composite strength is not decreased noticeably in relation with room temperature strength. The mechanical strength and ductility of the samples are increased by rising of applied pressure to (0-100 MPa) due to decrease grain size and better strength interface of alumina and alloy. When pouring temperature is increased, strength of alloy and composite and ductility increase (ca. 17%). Additionally, wear rate due of composite decreased in comparison to base alloy declined markedly (about 53%). This may be due to higher intrinsic alumina strength. Also, by applying pressure on molten metal during solidification, wear rate is noticeably lesser than similar gravity sample due to decreasing the grain size and markedly declining the porosity. The dominant mechanism for base alloy is adhesive wear and for composite is abrasive wear and delamination. Keywords Composite, Magnesium, Alumina, Infiltration casting, Spinel phase, Wear.