Products of aluminum matrix composites in the aerospace, military and automotive industries are mostly fabricated by stir casting method. However, fabrication of composite materials by this method when nanoparticles are used as reinforcements lead to the formation of lots of structural defects. In this study, copper coating of alumina reinforcement particles is investigated as a technique for improving the structure of Al-Al2O3 composites. Microstructural investigations using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and transmission electron microscopy (TEM) showed alumina particles are coated uniformly with copper shells. Copper coating of reinforcing particles significantly increases wettability of particles in the molten aluminum alloy, forms strong matrix-reinforcements interface and improves distribution of reinforcing particles within the matrix. Hardness, compressive strength, yield stress, tensile strength and elongation of composite samples are enhanced as results of improving the microstructure of composite materials by copper coating the alumina particles.

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