Effects of natural aging and reversion treatments on artificial aging behavior of 6000 series aluminum alloys

Three 6000 series commercial alloys (6061, 6022 and 6 N01) were aged at room temperature, reverted at temperatures above 473 K and finally aged at 448 K. The negative effect of room-temperature pre-aging on age-hardening at 448 K in 6061 and 6022 alloys was not varied by times of pre-aging longer than 10 days. In the 6061 alloy, reversion treatment at 573 K for 30 s resulted in a significant reduction in age hardening at 448 K. It is conjectured that rapid precipitation occurred during the reversion treatment because of the high degree of super saturation caused by its high solute content. Hardening by paint baking at 448 K for 1.2 ks of automotive body panels was largely improved by reversion treatments for 30 s at 523 K in 6061, at 523 K or 548 K in 6022 and at 548 K in 6N01. Concerning with maximum age-hardening at 448 K, improvement by reversion in the negative effect was the same temperature that improved paint bake response the most. The range of reversion temperatures at which the hardening was most improved tended to become narrower with increasing Mg and Si contents.