Process–Porosity–Property Relationships in Directed Energy Deposition (DED-Arc) of Al-Mg-Si Alloy

Directed Energy Deposition-Arc (DED-Arc) was employed to fabricate walls from a heat-treatable Al-Mg-Si alloy (EN-AW 6063) in order to investigate the influence of inter-pass thermal management on porosity evolution, microstructural development, and mechanical performance. Two deposition strategies were examined: Group I, which incorporated intermittent air cooling between successive layers, and Group II, which used a short inter-pass dwell time of 15 s without active temperature control, resulting in higher cumulative heat input. Mechanical characterization revealed superior tensile properties in Group II, with higher yield strength (Rp0.2) and ultimate tensile strength (Rm) in both build and scan directions compared to Group I. Hardness measurements along the build height showed systematic increase from the substrate toward the top of the wall, reflecting reduced thermal cycling and diminished over-aging in the upper regions. X-ray computed tomography demonstrated a pronounced reduction in porosity for Group II, which exhibited a lower porosity fraction and significantly finer pore morphology, with a mean equivalent pore diameter of 0.3 mm compared to 0.8 mm in Group I. Overall, the results demonstrate that minimizing inter-pass cooling time, despite higher cumulative heat input, promotes finer porosity and improved mechanical performance in DED-Arc fabricated EN-AW 6063.