Strategy for developing aluminum alloy-based solid structure with homogeneous properties in the overlapping direction using wire arc additive manufacturing

Abstract

This research investigates the strategy for developing large-scale solid aluminum structures with multi-bead multi-layer (MBML) overlapping using wire-arc additive manufacturing (WAAM). The study addresses challenges, i.e. material accumulation, surface irregularities, and inter-bead and inter-layer gaps, by examining deposits’ geometrical characteristics, process parameters, and deposition methods. Initial test coupon solid blocks are printed and analyzed using optical microscopy, and subsequent statistical optimization leads to the successful printing of a defect-free 140 mm × 150 mm × 28 mm solid block. The flat surface achieved in the MBML structure is attributed to maintaining an optimal overlap coefficient and a parabolic profile with the maximum width at the base. Microstructural analysis reveals the absence of fusion gaps, with an average porosity of 11.7 ± 2.45%, due to hydrogen evolution and reheating effects, with few larger pores near fusion lines. The microstructural and mechanical analyses confirm the homogeneity of properties along the overlapping direction (OD), with microhardness averaging 85.80 ± 6.63 HV0.1 and tensile strength of 161.55 ± 1.19 MPa with 2.18 ± 0.08% elongation. Microhardness fluctuations along the OD are attributed to fusion boundaries, partially melted and heat-affected zones. The research revealed that careful consideration of bead geometry and process parameters is crucial for achieving defect-free aluminum solid structures in WAAM through MBML overlapping.