An attempt was made to establish the elements that are able to affect the kinetics of the origin and growth of products of decomposition in aluminum-silicon alloys (silumins) alloyed with copper that in composition are close to eutectic. Values for the solubility of 32 elements in aluminum and copper at 500/degree/C were determined. Silver, germanium, and gallium were used to experimentally investigate the effect of elements on solid solution decomposition kinetics and alloy strengthening by heat treatment. The effect of additions on the electrical resistance of the alloy with heating and isothermal holding was also evaluated. The separate and joint effects of silver, gallium, and germanium additions on the mechanical properties were established. Electron microscopic investigations were carried out with oxide replicas. Microstructures for various alloy compositions and doping levels were assessed.