Method of manufacturing high-strength aluminum alloy extruded product excelling in corrosion resistance and stress corrosion cracking resistance

Abstract

A method of manufacturing a high-strength aluminum alloy extruded product which excels in corrosion resistance and stress corrosion cracking resistance, and is suitably used in applications as structural materials for transportation equipment such as automobiles, railroad carriages, and aircrafts. The method includes extruding a billet of an aluminum alloy containing 0.5% to 1.5% of Si, 0.9% to 1.6% of Mg, 0.8% to 2.5% of Cu, while satisfying the following equations (1), (2), (3), and (4),3≦Si%+Mg%+Cu%≦4  (1)Mg%≦1.7×Si%  (2)Mg%+Si%≦2.7  (3)Cu%/2≦Mg%≦(Cu%/2)+0.6  (4)and further containing 0.5% to 1.2% of Mn, with the balance being Al and unavoidable impurities, into a solid product by using a solid die, or into a hollow product by using a porthole die or a bridge die, thereby obtaining the solid product or the hollow product in which a fibrous structure accounts for 60% or more of an area-fraction of the cross-sectional structure of the product.