Microstructure and properties research of Al-Zn-Mg-Cu alloy with high strength and high elongation fabricated by wire arc additive manufacturing

In this study, Al-Zn-Mg-Cu alloys with high strength and ductility were successfully prepared by wire arc additive manufacturing technology. Innovatively, the effect of composite processing (heterogeneous particles and heat treatment) on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy arc additive manufacturing deposition was studied. After composite processing, the grain morphology of the deposition was successfully transformed from coarse columnar crystals to dense equiaxed crystals, and the precipitation of nano-precipitated phases was greatly promoted. The influence of microstructure on mechanical properties was deeply investigated. Because of the modification of the microstructure, the tensile strength of the depositions increased from 206.8 ± 14.3 MPa to 503.6 ± 10.1 MPa (horizontal direction) and 256.2 ± 13.1 MPa to 501.2 ± 10.0 MPa (vertical direction), and the elongation increased from 4.1 ± 0.9 % increased to 10.9 ± 1.0 % (horizontal direction) and 6.6 ± 0.3 % to 13.4 ± 0.3 % (vertical direction), and the hardness was also increased from 117.9 HV to 197.9 HV. Finally, investigations revealed that the composite processing not only promotes the simultaneous increase of strength and elongation, but also greatly improves the anisotropy of the deposition. Fine grain strengthening is the main mechanism of increasing elongation. Precipitation strengthening is the main mechanism of strength enhancement. This research can provide theoretical guidance for improving the strength and elongation of Wire Arc Additive Manufacturing Al-Zn-Mg-Cu alloys, thus promoting engineering applications.