Improved properties of wire arc direct energy deposited Sc/Zr-modified Al-Zn-Mg Alloy with low heat input

Wire arc direct energy deposition (DED) is gaining traction for manufacturing Al-Zn-Mg alloys as key materials in aerospace applications. However, current wire arc DED processes often fall short in achieving the desired balance between strength and ductility inherent to these alloys. In this study, we introduce an innovative Al-Zn-Mg alloy wire, enhanced with Sc and Zr, utilizing a low heat input printing method with a specific value of 160.5 J/mm, compared against a higher heat input of 377.1 J/mm as a control. This low heat input approach significantly refines grain structure, optimizes precipitate phases, and dramatically reduces porosity by 96.2%, from 0.73% to 0.028%. The as-deposited mechanical properties of the components achieved a ultimate tensile strength (UTS) of 406.5 ± 2.0 MPa, yield stress (YS) of 266.6 ± 0.7 MPa and an uniform elongation (EL) of 12.3 ± 0.6%. Following a solution treatment at 470°C for 3 hours and subsequent aging at 120°C for 24 hours, the UTS and YS increase to 566.9 ± 4.2 MPa and 512.3 ± 4.3 MPa, respectively, with an elongation of 9.9 ± 1.1%. Notably, the mechanical properties demonstrate an exceptional balance between high strength and ductility, addressing the low elongation challenge typically seen in 7xxx series alloys produced by wire arc DED. The contributions of grain refinement, η' phase, and Al₃(Sc,Zr) nano-strengthening to yield strength are quantified as 13.6%, 61.8%, and 24.6%, respectively. This research establishes a robust framework from both material composition and processing perspectives, advancing the strength capabilities of wire arc DED-produced high-strength aluminum alloys in aerospace applications.