Welding of additively manufactured aluminium alloy components: challenges and mitigation strategies

Abstract

Additive manufacturing (AM) has contributed to significant advances in the production of aluminium alloys, particularly through powder bed fusion (PBF) and directed energy deposition (DED) processes. However, joining of conventionally and additively manufactured components remains essential. This work focuses on the weldability of AM aluminium alloys using fusion and solid-state welding processes. The study analyses the microstructural evolution and mechanical properties, revealing a relationship between AM technology and joining process. In particular, fusion welding of PBF-laser beam (LB) produced aluminium alloys presented a significant limitation due to the high porosity level, especially in the weld zone near the PBF-LB base material. This region of high porosity, known as the pore belt region, has an enormous detrimental effect on the mechanical properties of the weld. This phenomenon is not observed when the welds are carried out by solid-state welding processes, which makes this group of welding processes very suitable for this type of material. On the other hand, fusion welding of aluminium alloys produced by wire arc additive manufacturing (DED-Arc or WAAM) exhibits a good stability and repeatability, analogous to conventional aluminium alloy welding practices. Rotational friction welding of DED-Arc-produced components presented an unexpected challenge. Due to the difference in ductility compared to conventionally manufactured parts, the process window for optimal process pressure was found to be very narrow and sensitive. The findings are confirmed by metallographic examination, hardness profile measurement, tensile and bend testing.