The stir casting method in aluminum composite manufacturing has the main weakness of particle distribution which reduces the mechanical properties of the composite. One way to increase the interfacial bond strength between reinforcement and matrix is by heating the reinforcement particles. The composite manufacturing process uses 6%wt Al2O3 ceramic reinforcement, the agitation process is carried out with a four blade impeller at 700 rpm at a temperature of 720 °C for 10 min. Composite castings are tested for hardness according to ASTM E-10 and tensile test referring to JIS Z2201. The test results show that the hardness and tensile strength of the composite increases with increasing treatment temperature on the particles. The highest hardness results at a treatment temperature of 300° were 51.31 BHN and 183.98 MPa. This is because preheating the particles can remove water vapor and gas from the surface of the particles which prevents wetting by the liquid metal. Preheat also removes impurities and changes the composition on the surface of the particles. A clean surface provides an opportunity to increase wettability, resulting in a strong interfacial bond.