Evolution of microstructure and properties in 2219 aluminum alloy produced by wire arc additive manufacturing assisted by interlayer friction stir processing

Wire arc additive manufacturing (WAAM) technology has potential advantages in the production of large-scale aluminum alloy components. However, as-deposited Al–Cu alloys produced by WAAM often suffer from porosity defects and coarse eutectic phases distributed along the grain boundaries, resulting in poor mechanical properties and hindering the applicability of WAAM to prepare aluminum alloy components. Herein, 2219 aluminum alloy was prepared using WAAM assisted by interlayer friction stir processing (FSP). Porosity defects in the as-deposited materials were eliminated, and coarse eutectic phases were broken and dissolved into the α-Al matrix via interlayer FSP, improving the mechanical properties of the components. The specimens processed by WAAM + interlayer FSP were subjected to different thermal cycling at different locations. The top-layer stir zone (SZ) was not affected by thermal cycling during the additive manufacturing process, and mechanical properties in the SZ were superior to those in the middle region. Compared with the as-deposited materials prepared by WAAM, the yield strength (YS) and ultimate tensile strength (UTS) in the middle region along the horizontal direction of the components manufactured by WAAM + interlayer FSP increased from 118 to 143 MPa and from 255 to 277 MPa, respectively. Further, the ultimate fatigue strength increased from 97 to 139 MPa. The YS and UTS along the vertical direction were 140 and 268 MPa, respectively, which are slightly lower than those along the horizontal direction. This is due to the small overlapping between the two adjacent SZs. The partially melted zone (PMZ) between the SZs was not completely eliminated, and the θ phase in the PMZ was mostly distributed along the grain boundaries.