The invention belongs to the field of aluminum
alloy production technologies, and relates to a technology capable of reducing generation of coarse grains on the surface of a vehicle
extrusion-forged bar. An aluminum
alloy is prepared from the raw materials in percentage by weight: 1.07-1.12% of Si, less than or equal to 0.1% of Fe, 0.01-0.04% of Cu, 0.62-0.65% of Mn, 0.88-0.93% of Mg, 0.15-0.18% of Cr, less than or equal to 0.03% of Zn, 0.02-0.05% of Ti, less than or equal to 0.03% of a single
impurity, less than or equal to 0.1% of an
impurity total, and the balance of Al, wherein the ratio of the Mg to the Si is 0.79-0.87. An aluminum
alloy cast
ingot prepared through the formula is subjected to
solid solution heat treatment after
extrusion, on-line
water spray quenching treatment and stretch straightening, each technological parameter is controlled seriously, after an aluminum alloy
extrusion bar is subjected to 545 DEG C*1 h
solid solution heat treatment, the section has no the coarse grains, and the surface has no the coarse grains; and after the bar is forged, the thickness of a coarse grain layer of the section is less than or equal to 3 mm, and mechanical performance after170 DEG C*8.5 h can reach: the yield strength RP 0.2 is greater than or equal to 320 Mpa, the tensile strength Rm is greater than or equal to 360 Mpa, and the elongation percentage A is greater than or equal to 10%.