Experimental and numerical study on the influence of wire feeding rate on the metal transfer, molten pool behavior, and surface morphology in direct energy-deposited Al‑Zn‑Mg‑Cu alloy

Abstract

To address the challenges of deposition accuracy in wire-arc directed energy deposition (DED) caused by complex thermal dissipation, this work investigates the deposition characteristics of Al-Zn-Mg-Cu alloy deposits through a combined experimental and numerical approach. Experimentally, a high-speed camera with background laser and current/voltage sensors was employed to capture metal transfer dynamics and electrical waveforms under different wire feeding rates (WFRs). Numerically, a three-dimensional transient computational fluid dynamics model integrating electromagnetic, thermal, and fluid flow fields was established using ANSYS Fluent, with an adaptive grid technique and a “heat-force-current” coupling algorithm to simulate molten pool behavior. Results demonstrate that at a low WFR, insufficient lateral spreading causes “bead-like” defects and interlayer trenches, while excessive WFR (> 5 m/min) triggers molten pool overflow and spatter due to elevated current levels. A transition in the dominant flow pattern from the traveling direction to the lateral direction was identified as WFR increased. Optimal deposition accuracy was achieved at a WFR of 4 m/min, yielding surface roughness values of S_a = 115 μm, S_z = 724 μm. Furthermore, layer width exhibited higher sensitivity to WFR variations than layer height. These findings provide a critical quantitative regulation framework for optimizing the deposition stability and geometric fidelity of DED high-strength aluminum alloys.