Influence of deposition strategy of structural interface on microstructures and mechanical properties of additively manufactured Al alloy

Abstract Mechanical properties of the structural interface are significantly important for the wire + arc additively manufactured (WAAM) component who keeps the substrate as a part. Two deposition strategies using power sources of pulse advanced cold metal transfer (CMT-PA) and pulse metal inert gas (MIG-P) as the first layer were designed to build WAAM 2319 Al alloy walls. The microstructure and mechanical properties of the structural interfaces and the entire parts were investigated. Key findings demonstrated the deposition strategy has little influence on the macro-mechanical properties of the WAAM parts. All the as-deposited parts were fractured on the WAAM metal 5–7 layers away from the interface boundary, although the bottoming arc mode had a great influence on the geometry and microstructure of the interfaces. Microcracks were initiated from the micropores or coarse θ particles. After the T6 heat treatment, the entire WAAM part containing the substrate exhibited a homogeneous feature of mechanical properties. The mean yield stress and ultimate tensile stress achieved over 330 MPa and 430 MPa due to the precipitation of a considerable number of nano-sized metastable θ′ phases. Whereas the bottoming strategy of MIG-P, which will effectively enlarge the load-bearing area and increase materials utilization rate, is suggested during the design of WAAM components.