Structure and corrosion behavior of friction stir weld joint of 2195 Al-Li alloy

Microstructures, electrochemical behavior and corrosion feature of different locations in 2195-T8 Al-Li alloy FSW joint were investigated. The parent metal possesses fiber-like grains, but the nugget zone is featured with fully recrystallized grains with size less than 10 μm. The strengthening precipitates of the parent metal are T1 (Al₂CuLi) and θ' (Al₂Cu). In the thermo-mechanically affected zone, most T1 and all θ' are re-dissolved, but all T1 and θ' are re-dissolved in the nugget zone. From the parent metal to the nugget zone, the potential increases. Accordingly, galvanic corrosion occurs on the FSW joint surface, the parent metal undertakes anodic current and the nugget zone undertakes cathodic current. In the intergranular corrosion medium, superficial corrosion occurs on the nugget zone surface, but corrosion penetrates inside the parent metal.