Tomography analysis of Al–Mg alloys manufactured by wire-arc directed energy deposition with different metal transfer modes

[Display omitted] •Porosity reduction in WAAM 5356 aluminum alloy, without adding any extra equipment, using the pulsed-AC metal transfer mode.•The main cause of the porosity in aluminum alloys is the trapped hydrogen that creates small and spherical pores.•The micropores are mainly located in the contour parts of the walls.•Micropore bands formed with small and spherical pores are observed at the inter-layer boundaries.•The porosity levels are lower in the double-bead walls than in the single-bead walls. The interest in aluminum-magnesium alloy additive manufacturing through Wire-arc Directed Energy Deposition (DED) technology has substantially grown in recent years. The main challenge in additive manufactured aluminum-magnesium alloys is the occurrence of porosity. In this context, Gas Metal Arc Welding (GMAW) based additive technology is suitable for aluminum printing as it allows high deposition rates and reduces porosity levels through alternative metal transfer modes without adding any extra equipment. Therefore, this research explores the effects of these alternative metal transfer modes, which determine the current signal shape and polarity, on the distribution and morphology of micropores using X-ray computed tomography in both single-bead and double-bead walls. The novelty of this paper lies in the comparison of the porosity obtained using alternative transfer modes, which, unlike CMT (Cold Metal Transfer) modes, have not been exhaustively analyzed. Additionally, to date, there has been no comprehensive comparison of the porosity results obtained in single walls and overlapped walls. The results demonstrate that pulsed-AC transfer mode with a current signal featuring variable polarity yields acceptable porosity fraction values of less than 0.04% in single-bead walls and less than 0.01% in double-bead walls, achieving high productivity.