Producing combined high strength and high corrosion resistance in Al-Zn- MG-CU alloys

摘要

The method of thermally treating an article composed of an alloy consisting essentially of aluminum, 4 to 8% zinc, 1.5 to 3.5% magnesium, 1 to 2.5% copper, and at least one element selected from the group consisting of 0.05 to 0.3% chromium, 0.1 to 0.5 manganese, and 0.05 to 0. 3% zirconium, which method includes the steps of solution heat treating the article, then precipitation hardening the article at 173° to 325° F., then subjecting the article to a time and temperature within the perimeter ABCD of FIG. 4, and then again precipitation hardening at 175° to 325° F.