Systematic generation of pores in AlSi10Mg components using specific shielding gas conditions in the GMAW-WAAM process

Wire Arc Additive Manufacturing (WAAM) utilises the process of arc welding for the additive manufacturing of components and is suitable for functionally graded additive manufacturing. The aim of the present study is to illustrate the possibility of systematically generating pores in additively manufactured AlSi10Mg components when customised shielding gas conditions are used. For this purpose, Gas Metal Arc Welding-WAAM was used with variation of shielding gas composition and shielding gas quantity to produce vertical multilayer walls consisting of AlSi10Mg. Micrographs revealed the well-known Al matrix with Al-Si eutectic and statistical analysis showed strong influence of shielding gas composition on porosity, number of pores and pore diameter. Using N₂ + 10 vol% H₂ as shielding gas increased the porosity and pore diameter significantly while using Ar or Ar + 10 vol% H₂ led to smaller pores which, however, are present in larger numbers. Varying the amount of the respective shielding gas between 3 Nl/min, 12 Nl/min, 18 Nl/min and 30 Nl/min had only a minor influence on porosity, number of pores and pore diameter. However, the usage of 3 Nl/min led to higher porosity when Ar shielding gas was used and to less porosity and pore diameter when N2 + 10 vol% H2 was used. Finally, when Ar + 10 vol% H2 was used, the parameter set with 3 Nl/min was not suitable for the manufacturing of a wall with WAAM. The use of the N₂-H₂ gas mixture appears to be a promising approach for manufacturing of continuously porous structures whereby nitride precipitates appear to stabilise the pores during remelting. However, as only few samples were tested, a stable process window has not been established yet.