Effect of aging on mechanical properties and localized corrosion behaviors of Al-Cu-Li alloy

The effects of aging on mechanical properties, intergranular corrosion and exfoliation corrosion behaviors of a 2197 type Al-Li alloy were investigated, and the mechanisms were studied through microstructure observation and electrochemical measurement of simulated bulk phase. The main strengthening precipitates of the alloy aged at 175 ℃ and 160 ℃ are δ′ and T1. T1 precipitation in the alloy aged at 160 ℃ is delayed, which results in its slower age strengthening and over-aging behavior than the alloy aged at 175 ℃. Meanwhile, aging temperature of 160 ℃ causes more uniform distribution and finer size of T1, resulting in its better strengthening effect. As aging time and aging temperature are increased, the size of T1 at grain boundaries and the width of PFZ along grain boundaries are increased, leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion. It is suggested that better comprehensive properties can be obtained when the alloy is aged at 160 ℃.