Microstructure evolution and mechanical properties of Al–Cu–Mn–Cd alloy fabricated by CMT-wire arc additive manufacturing

The high-performance additive manufacturing of relatively small aluminum alloy components has been widely proven successful. However, wire arc additive manufacturing (WAAM) has always been challenging in achieving uniform microstructure and high mechanical properties when manufacturing large-sized parts. Therefore, this study used cold metal transition wire arc additive manufacturing (CMT-WAAM) to prepare Al-5.49Cu-0.4Mn-0.29Cd (ACMC) alloy to obtain a uniform microstructure and improve its mechanical properties. The results show that the as-deposited (AD) samples have an obvious layered deposited structure. The grains in the microstructure are all equiaxed crystals and a large amount of copper-rich eutectic phase precipitates at the grain boundaries. After heat treatment, the vast majority of the eutectic phase dissolves, and θ'phase, with a size of 100–200 nm, uniformly precipitates in the α-Al matrix. The ultimate tensile strength (UTS) and yield strength (YS) of the heat-treated (HT) specimen can reach 483.7 MPa and 412.3 MPa, respectively. There is no significant difference in the mechanical properties between the transverse and longitudinal directions of thin-walled samples. Based on experimental results and theoretical analysis, the strengthening mechanism and fracture mechanism of CMT-WAAM aluminum alloy were revealed. This work provides a theoretical basis for the microstructure optimization and mechanical performance improvement of ACMC alloy, which is of great significance for the high-performance preparation of large-sized components in the aerospace field.