Method for manufacturing aluminum alloy extruded material with high strength and excellent in SCC resistance and hardenability

A method for manufacturing an aluminum alloy extruded material, the method comprising:

• casting a billet of an aluminum alloy composition including, by mass:
• 6.0 to 8.0% of Zn, 1.5 to 3.0% of Mg, 0.20 to 1.50% of Cu, 0.10 to 0.25% of Zr, 0.005 to 0.05% of Ti, 0.15 to 0.35% of Mn, 0.25% or less of Sr, and 0.25 to 0.50% of a total of [Mn+Zr+Sr], and a balance including Al and unavoidable impurities;
• cooling the billet at a rate equal to or higher than a cooling rate of 50° C./hr after homogenization treatment at 480 to 520° C. for 1 to 14 hours;
• extruding an extruded material by using the billet subjected to the homogenization treatment;
• cooling the extruded material at a rate of a cooling rate of 50 to 750° C./min after the temperature of the extruded material is dropped by 48° C. or more to 325 to 400° C. directly after extruding;
• and
• applying two-stage artificial aging treatment at 90 to 130° C. for 1 to 8 hours and at 130 to 180° C. for 1 to 20 hours to the extruded material.