Graphite flakes (Gf)/Si/Al composites have been fabricated with different volume fraction of graphite by vacuum gas pressure infiltration. In the composites, the addition of Si played a role of spacing apart graphite layers, which can produce voids between layers for the infiltration of molten aluminum. Microstructural characterization indicated that the reinforcements were fairly distributed in the Al and a clean interface lacking of Al3C4 phase was formed between Al and Gf. With the increase of Gf from 39 to 81 vol%, the longitudinal thermal conductivity (TC) of composites increased from 294 to 390 W/m K, but the open porosity increased from 1.85 to 6.03%. Besides, a joint M1–M2 prediction model was established, which considered that the microstructure of composites lies in between two models: (M1) a layered structure in binary metal-particle composites and (M2) ternary composites that oriented flakes randomly distributed in metal-particle confirmed a better theoretical prediction of TC.
