Numerical and experimental investigation of aluminum alloy additive manufacturing with a coaxial quadruple flat-top laser

To address the limitations inherent in traditional side-axis laser additive manufacturing, such as directional dependence and uneven heating, this study developed a coaxial quadruple flat-top laser directed energy deposition (CWL-DED) system. Using an Al 5052 substrate and ER 5356 filler wire, optimal processing parameters (P=5000W, V=10mm/s, S=2.3m/min) were determined through systematic single-variable experiments. CFD simulations revealed stable liquid bridge heat transfer at the melt pool center with peak temperatures reaching 1239.12 K, and intense trailing-edge convection with a backflow velocity approaching 1 m/s. Microstructural characterization identified a three-zone gradient structure: columnar grains in the lower zone (65.42 μm), mixed grains in the middle zone (88.62 μm), and refined equiaxed grains in the upper zone (49.58 μm), indicating a non-monotonic grain refinement trend from lower to upper area. EBSD analysis revealed a dominant {100}∥Y 1 fibrous texture with peak intensity of 11.05 in the middle zone. Microhardness peaked at 67.91 HV in the upper zone, and lattice distortion was governed by the coupled effects of solidification rate gradient and thermal stress. EDS analysis confirmed preferential Al 3 Mg 2 enrichment at grain boundaries, spatially correlated with melt pool convective transport paths. These findings provide a theoretical basis for optimizing the CWL-DED process for aluminum alloys.