Al-4.5 wt. % Cu matrix composites reinforced with in situ SiC particles were synthesized using direct reaction synthesis (DRS). The microstructure and tensile properties of the in situ composites were examined by optical microscopy (OM) and transmission electron microscopy (TEM). The results showed that the in situ SiC particles could be obtained through the appropriate control of the fabrication parameters. The heat released by the formation of TiC effectively promoted the formation of SiC. The size of the in situ SiC particles in the matrix was about 0.2 μm.