Simultaneous Strength and Ductility Enhancement of Wire-Arc Directed Energy Deposited Al-Cu Alloy by Interlayer Laser Shock Peening

Abstract

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 0.7~1.3mm 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%, 17.0%, and 27.3%, respectively. The introduction of high-density dislocations and compressive residual stress, coupled with local recrystallization induction, are the primary effects of LSP on the microstructure. Moreover, the combined effect of the resultant compressive residual stress and the thermal input of the subsequent layers creates a tight metallurgical bond 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.

Keywords: Laser shock peening, Wire-arc directed energy deposition, Defects, Residual stress, Grain refinement.