Arc-DED additive manufacturing of high-Zn-content Al-Zn-Mg-Cu alloy assisted by interlayer remelting and mechanical hammering

Arc-directed energy deposition (Arc-DED) is a promising additive manufacturing technology for fabricating medium-to-large-scale and lightweight structural components. The development of high-strength aluminum alloys is crucial for optimising the performance of these Arc-DED-manufactured components. However, achieving a high tensile strength remains a major challenge for Arc-DED fabricated aluminum alloys. In this work, high-Zn-content Al-Zn-Mg-Cu alloys were fabricated by Arc-DED, with a small amount of TiC and Al3Ti introduced for grain refinement. In-situ Zn alloying elevates the Zn content to above 9 wt.%, which plays a dominant role in achieving the ultra-high strength. This in-situ alloying is realised by pre-placing Zn foils on the top surface of each deposited layer. The combined interlayer remelting and mechanical hammering process promotes Zn homogenisation and improves the deposition quality. After T6 treatment, the high Zn content promotes the formation of fine, uniform and high-density nanoprecipitates, resulting in an ultra-high strength of 626 MPa.