The effects of amount, dispersion, nature and doping method of reinforcing particles on the structural parameters and mechanical properties of the AK15 aluminium alloy are investigated. Micro-sized particles of aluminium oxide, silicon carbide and VK6 hard alloy (94% WC, 6% Co) are used as the reinforcing phases. The particles content varied from 0.5 to 5% wt. in the composites. As established, the composites have a more dispersed structure than the original matrix alloy, $i.e.$ the particles act as refining agents. The silumin with 0.5–1% microparticles shows increased tensile strength and specific elongation, which may be associated with the refinement of the alloy structural elements. However, a further increase in the reinforcing phase content leads to a deterioration of the mechanical properties, which is explained as a result of the particles agglomeration.