Microstructure and weakening mechanism of additive-manufactured Al–Cu alloy under different heat input

The heterogeneous microstructure and mechanical properties of wire-arc additive manufactured 2219 Al–Cu alloy at several heat inputs (HIs) by adjusting the wire feeding speed were investigated. The partially melted zone (PMZ) was regarded as the weak region, and the weakening mechanism was analysed. Results indicated that the size and volume fraction of equiaxial grain increased with higher HI. The mass fraction of the segregated eutectics increased and the concentration of solid solution Cu in the α-Al matrix decreased. In addition, the morphology and distribution characteristics of eutectics were distinctly different at the inter-layer zone and inner-layer zone. The eutectics at the inter-layer PMZ were coarsened and continuous owing to the Cu solid-state diffusion and liquation.