The microstructures of AA5083 in AA5083/SiC co-continuous ceramic composites (C4) fabricated by gas pressure infiltration with 10 and 20 PPI SiC foams and by gravity infiltration with 10 PPI SiC foam were characterized. The porosity and hardness were evaluated through optical microscopy and Vickers hardness testing. This paper examines the effects of pressure and SiC foam pore size on the microstructural properties of AA5083 in these composites. AA5083 in the 10 PPI composite fabricated by gas pressure infiltration had a smaller average grain size, higher average hardness, and lower average porosity than in the 10 PPI composite fabricated by gravity infiltration. It also had a larger average grain size and higher average hardness and porosity than in the 20 PPI composite fabricated by gas pressure infiltration. Hardness was observed to increase with decreasing distance from areas of SiC within each composite.