The structure and strength of Al−xSi−2wt.%Cu (x = 15, 17 and 20wt.%) alloys obtained by directional solidification at a rate of 0.1 and 0.8mm/s are investigated. It is shown that the tensile strength increases with an increase in the rate of solidification due to a decrease in the size of eutectic silicon and the transformation of its crystal flake into a fine-fiber one. In addition, there was an increase in tensile strength due to an increase of the share of the intermetallic phase, exceeding the reduced tensile strength due to an increase in the amount of the α-Al phase. An increase in the silicon content in the samples during solidification at a rate of 0.1 mm/s does not lead to a change in structure and strength. At a higher rate of solidification, there is a reduction of the share of eutectic and a decrease in strength.

Friction coefficient and wear of hypereutectic alloy of aluminum with 15wt.% silicon with supermodified eutectic structure without primary silicon crystals were studied. Such hypereutectic alloy with eutectic structure was obtained by directional solidification with the rate 1mm/s. It has higher strength and plasticity, higher resistance to wear and lower friction coefficient than hypereutectic alloy of aluminum with 20 wt.% silicon. After modification by strontium its tribological properties are superior to those of hypereutectic commercial alloy.

Young’s modulus and the logarithmic decrement of oscillations at a frequency of ~100 kHz as well as the subgrain size and residual stresses in the strontium modified alloy of aluminum with 15 wt % silicon have been studied. The alloy was obtained with a solidification rate of 1 mm/s at the shifted eutectic point. The dependence of inelastic dislocation deformation on the applied oscillating stress has been obtained and analyzed. The effect of strontium modification on the microstrain diagram can be accounted for by transformation of the lamellar fiber structure of eutectic silicon into a superfine fiber structure.