Influence of the rate of directional crystallization and silicon content on the structure and strength of the Al–Si–Cu alloy

The structure and strength of Al$_x$Si-2wt.%Cu ($x$ = 15, 17 and 20 wt.%) alloys obtained by directional solidification at a rate of 0.1 and 0.8 mm/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 $\alpha$-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.