Simultaneous strength and ductility enhancement of wire-arc directed energy deposited Al–Cu alloy by interlayer laser shock peening

Wire-arc directed energy deposition (wire-arc DED), recognized for its ability to produce large-scale parts, has gained considerable attention. However, a critical issue with this method is the high prevalence of internal porosity defects found in the manufactured aluminum components, adversely impacting their mechanical properties. For the first time, this study introduces in-situ interlayer Laser Shock Peening (LSP) during wire-arc DED of 2319 aluminum alloy. The thickness of each deposited layer was meticulously regulated within the 0.7–1.3 mm range utilizing a spiral-path oscillation mode. Following this process, LSP was applied to the top surface of each layer. Compared to the as-deposited samples, interlayer LSP-treated samples showed a significant decrease in pore numbers by 73.9% and a reduction in the total area by 87.4%. Furthermore, the LSP-treated samples displayed improved mechanical properties with increases in ultimate tensile strength, yield strength, and elongation by 20.1%, 19.1%, and 27.3%, respectively. The primary impact of LSP on the microstructure is the generation of high-density dislocations, providing a driving force for grain refinement during subsequent layer heat input. With the combined effects of heat input and dislocation density, samples treated with LSP form a tight metallurgical bound around the closed pores. This process of effective defect elimination and an increased dislocation density between the layers results in a simultaneous improvement in strength and plasticity.