In the present study aluminum-silicon matrix composites reinforced with silicon carbide particles and mixture of silicon carbide and 10% graphite particles were fabricated by gas pressure infiltration of molten alloy in a porous preform and their properties were characterized. For this purpose, a pressure chamber capable of providing vacuums up to 10 -2 bars and pressures up to 20 bars at temperatures up to 800 ° C was designed and built from HP45 super alloy. First, a large number of initial tests were carried out to determine the main parameters that influence the infiltration of the melt in the preforms. To improve the melt infiltration in the preforms, the base alloy was modified by adding magnesium and the silicon carbide particles were modified by an oxidation treatment. It was also observed that machining grooves on the bottom surface of aluminum-silicon ingots improved the melt infiltration in the preform. Infiltratioof the melt was conducted at various temperatures and pressures. Finally, the suitable infiltration temperature and pressure for complete filling of the preforms were determined to be 700 ° C and 10bar, respectively. It was observed that the melt infiltration pattern included the breaking of the oxide layer at the ingot surface, preferential infiltration from preform-mold interface towards the end of the mold followed by lateral infiltration towards the center of the preform. Microstructure evaluation of the optimized samples indicated the complete penetration of the melt in the preforms, good quality of the matrix-reinforcement interfaces and presence of about 60% reinforcement in the fabricated composites. Evaluation of the mechanical properties of the fabricated composites showed 105% and 34% improvement in the hardness and yield strength of the samples reinforced with silicon carbide particles in comparison with the base alloy, respectively. These values were 83% and 16%, respectively, for the sample reinforced with the mixture of silicon carbide and graphite particles. Tribological studies showed that addition of the reinforcement particles did not change the wear mechanism of the base alloy but only reduced its wear rate. Addition of graphite to the reinforcement resulted in smaller coefficient of friction and greater wear rate. Keywords Aluminum matrix composite, Hybrid composite, Gas pressure infiltration