The invention relates to a cast aluminum-
silicon alloy for an engine
cylinder head and a heat treatment process. The
alloy comprises the following
chemical ingredients in percentage by weight: 5.0 to 7.0 percent of Si, 3.0 to 4.0 percent of Cu, 0.2 to 0.4 percent of Mg, 0.1 to 0.3 percent of Mn, 0.10 to 0.20 percent of Zr, 0.15 to 0.25 percent of Ti, 0.01 to 0.05 percent of B, 0.02 to 0.09 percent of Sr, 0.1 to 0.3 percent of
rare earth (RE), less then 0.3 percent of Fe and the balance Al, wherein the
rare earth (RE) adopts mixed
rare earth. The heat treatment process comprises the following steps: carrying out primary solution at a temperature between 490 DEG C and 505 DEG C, and carrying out heat insulation for 4 to 6h; carrying out secondary solution at a temperature between 510 DEG C and 525 DEG C, carrying out heat insulation for 6 to 10h, and carrying out
quenching by hot water of 60 to 80 DEG C; and carrying out aging treatment with parameters of the aging temperature being 155to 165 DEG C and the heat insulation time being 5 to 9h, and carrying out cooling in the air. All
alloy elements of the cast aluminum-
silicon alloy provided by the invention are reasonably matched, good mechanical performance is realized, at a normal temperature, the tensile strength reaches 325 to 355MPa, the tensile stretch is 2.5 to 5.5 percent, at a high temperature of 250 DEG C, the tensile strength reaches 240 to 270MPa, and the tensile stretch is 3.0 to 5.5 percent, after the heating
processing technology, the
heat resistance performance of the alloy is improved, and the
casting defect is reduced.