Effect of heat treatment on microstructure and corrosion behavior of AlCu alloy fabricated by wire arc additive manufacturing

This study investigated the effect of heat treatment on the microstructure and corrosion behavior of the Wire Arc Additive Manufacturing (WAAM) 2319 Al alloy. The results showed that the solid solution treatment and the artificial ageing significantly increased the microhardness of the alloy, and the second phase of the alloy changed from a continuous to a dispersed distribution. Heat treatment led to an increase in pores, and the number of small-size pores increased significantly with the ageing time; this increased the risk of crevice corrosion. The as-deposited WAAM 2319 Al alloy, characterized by an α-Al matrix and coarse intergranular intermetallics Al₂Cu, underwent galvanic corrosion, which severely damaged the passivation film. The solid solution treatment alleviated this by dissolving the coarse intergranular intermetallics and improving corrosion resistance. During artificial ageing, the corrosion potential decreased gradually as the size and number of precipitated phases increased. Pitting corrosion was the most severe, and corrosion resistance was lowest in the solid solution + peak ageing state.