Layer-wise comparison of the coupled evolution of pores and microstructure in coaxial wire-laser directed energy deposition of 205C/7075 aluminium alloy: numerical simulation and experiment

Abstract The synergistic distribution characteristics of microstructures and pores in different deposition layers exhibit significant variations in the coaxial wire-laser directed energy deposition (DED) of heterogeneous aluminium alloys due to differences in material properties and thermal distribution. A macro–micro coupled model for grain growth and pore evolution was established to describe the molten pool solidification process in the coaxial wire-laser DED of 205C/7075 aluminium alloys in this study. The temperature field distribution, solidification parameters, pore distribution, microstructure, and the coupled evolution behaviour of grains and pores in different deposition layers were investigated. This study reveals that the sizes of columnar and equiaxed grains, as well as the degrees of solute and hydrogen accumulation are greater in the deposition layers of the 7075 aluminium alloy than in those of the 205C aluminium alloy, whereas the molten pool length exhibits the opposite trend. The average grain size in the pore-adjacent region increases from 84.06 to 138.91 μm from the transition layer C2 to the top deposition layer B of the 7075 aluminium alloy. The porosity and average pore diameter are higher in the transition layer C2 than in the top deposition layer B of the 7075 aluminium alloy. The solute and hydrogen accumulation are greater in the bottom deposition layer A than in the transition layer C1 of the 205C aluminium alloy. This study provides a theoretical basis for the synergistic regulation of microstructure and porosity in the coaxial wire-laser DED of heterogeneous aluminium alloys.