Intergranular corrosion of an Al-Cu-Li alloy: The influence from grain structure

The intergranular corrosion in a partially recrystallized 2A97 Al-Cu-Li alloy at various tempers was investigated. Immersion tests showed that the T6-tempered alloy was susceptible to intergranular corrosion (IGC) and intersubgranular corrosion (ISGC), and local corrosion preferentially initiated and propagated at subgrain boundary. The IGC and ISGC sensitivity decreased notably in the T8-tempered alloy and intragranular pitting dominated the corrosion in this case. The precipitates and solutes distribution at grain and subgrain boundary in T6- and T8-tempered alloy were characterized by TEM, STEM-EDX and APT to address the key influencing factor to the localized corrosion. ● Subgrain boundary is more sensitive to corrosion than grain boundary at T6 temper. ● Locally enriched Al 2 Cu phase on subgrain boundary facilitates local corrosion. ● Pre-stretching decreases the corrosion susceptibility of grain and subgrain boundary. ● Cu-rich film protects grain boundary from being attacked at T8 temper.