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Abstract:In order to build a better understanding of the relationship between depositing mode and porosity, microstructure, and properties in wire + arc additive manufacturing (WAAM) 2319-Al components, several Al-6.3%Cu deposits were produced by WAAM technique with cold metal transfer (CMT) variants, pulsed CMT (CMT-P) and advanced CMT (CMT-ADV). Thin walls and blocks were selected as the depositing paths to make WAAM samples. Porosity, microstructure and micro hardness of these WAAM samples were investigated. Compared with CMT-P and thin wall mode, CMT-ADV and block process can effectively reduce the pores in WAAM aluminum alloy. The microstructure varied with different depositing paths and CMT variants. The micro hardness value of thin wall samples was around 75 HV from the bottom to the middle, and gradually decreased toward the top. Meanwhile, the micro hardness value ranged around 72-77 HV, and varied periodically in block samples. The variation in micro hardness is consistent with standard microstructure characteristics.

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Restricted by the type of commercial aluminum wire, 2024 aluminum alloy cannot be built through conventional single wire + arc additive manufacturing technology. By simultaneously feeding two wires (ER2319 and ER5087) and adjusting the wire feed speed, 2024 aluminum alloy deposits can be achieved with double-wire + arc additive manufacturing process. Heat treatment procedures (solution + natural/artificial aging) were conducted for further improving the properties. The microstructure and mechanical properties of as-deposited and heat-treated 2024 aluminum alloy deposits were tested and analyzed. The microstructure differed in different conditions. Obvious dendrite morphology in as-deposited condition disappeared after heat treatment, and the phases turned to be α-Al + Al2Cu from α-Al + Al2Cu + Al2CuMg. After heat treatment, layer distributing characteristics of the phases became obvious. Post-deposition heat treatment can improve the micro hardness, strength and horizontal elongation of WAAM 2024 aluminum alloy deposits. The elongation along vertical direction decreased.