Abstract: A cast aluminum alloy vehicle wheel has a central disk, a rim, and a rim carrying portion located between the rim and the central disk. The rim has an end or tip portion that is the farthest portion of the rim from the disk, and a barrel portion is located between the rim carrying portion and the rim end. The microstructure of the metal provides a dendritic arm spacing (DAS) that is smaller at the rim end than at the rim barrel. Additionally, the DAS of the barrel portion is less then at the central disk. The DAS of the rim carrying portion is equal or less then the DAS of the barrel portion on the rim. A high strength wheel is provided, especially at the rim.

Abstract: A casting mold has a main body provided with a vent hole opened up in a casting space of said main body. The improvement is characterized in that the vent hole is provided with air discharging means and air feeding means which are disposed at the vent hole and the air discharging means and air feeding means are suitably selected so that air within the casting space can be discharged and a pressurized air can be fed toward the casting space through the vent hole.

Abstract: A paint film structure formed on an aluminum member or aluminum alloy member has a first paint film layer formed on a surface of the aluminum member or aluminum alloy member and a second paint film layer formed on a surface of the first paint film layer, the first and second paint film layers being chiefly composed of a colloidal silica, an organoalkoxysilane part hydrolysis condensation product, and a polymer or copolymer of an unsaturated ethylenic monomer, polymeric content or copolymeric content of the unsaturated ethylenic monomer in the first paint film layer being less than polymeric content or copolymeric content of the unsaturated ethylenic monomer in the second paint film layer.