On the Intergranular Corrosion and Hardness Evolution of 6xxx Series Al Alloys as a Function of Si:Mg Ratio, Cu Content, and Aging Condition

The intergranular corrosion (IGC) and hardness associated with 6xxx series aluminum alloy sheets, varying in composition (namely Si: Mg ratio and Cu content), were systematically studied in four different aging conditions. The IGC of each alloy was studied using ASTM G110, scanning electron microscopy, and optical microscopy. Scanning transmission electron microscopy was also used to rationalize the grain boundary chemistry of the relevant alloys. It was revealed that the severity of IGC depends on the continuity and type of grain boundary phases. The property space reported herein reveals prospects for the optimization of 6xxx series alloy compositions.