Microstructures and mechanical properties of Al-Zn-Mg aluminium alloy samples produced by wire + arc additive manufacturing

To study the forming rule, microstructures and mechanical properties of Al-Zn-Mg alloy samples produced by wire + arc additive manufacturing (WAAM), a metal inert gas (MIG) arc was used as the heat source and 1.2-mm-diameter Al-6.2Zn-2.2Mg welding wires were used as the raw materials during single-pass, single-layer deposition and single-pass, multilayer deposition. In the single-pass, single-layer deposition, as the heat input increased, the number of ripples on the weld bead decreased, thereby making the surface smoother. Furthermore, under different parameters, there were always pores in the cross-section of the weld beads. In the as-deposited material, the elements were unevenly distributed due to the layer-by-layer deposition. There were two types of pores in the as-deposited material: pores caused by the presence of hydrogen and those caused by the burning loss of zinc. The as-deposited material exhibited an average hardness of 112 HV. The horizontal test samples exhibited an average tensile strength of 324 MPa, a yield strength of 208 MPa, and an elongation of 9.66%. The vertical test samples exhibited an average tensile strength, yield strength and elongation of 299 MPa, 188 MPa and 8.98%, respectively. Moreover, the samples exhibited mixed ductile-brittle fractures.