Abstract
Abstract
This study investigates the development of high-strength and corrosion-resistant Al–7Mg-based alloys fabricated by laser-directed energy deposition (L-DED) using Sc/Zr and Zn/Zr modifications. Process optimization enabled the fabrication of crack-free deposits with low porosity. Sc/Zr addition produced substantial grain refinement, reducing the average grain size from 108.06 ± 56.32 µm in the base alloy to 11.70 ± 7.97 µm and 9.93 ± 6.61 µm in the 0.2Sc–0.5Zr and 0.4Sc–0.5Zr alloys, respectively. Zn/Zr modification also markedly refined the microstructure, resulting in average grain sizes of 15.12 ± 10.31 µm and 16.56 ± 13.26 µm in the 2Zn–0.5Zr and 4Zn–0.5Zr alloys, respectively. After heat treatment, Al–7Mg–0.4Sc–0.5Zr exhibited the best mechanical performance, achieving a yield strength of 304.8 ± 6.0 MPa, an ultimate tensile strength of 424.1 ± 6.7 MPa, and an elongation of 11.1 ± 0.8%. Al–7Mg–0.2Sc–0.5Zr demonstrated the highest corrosion resistance, with the lowest weight loss and corrosion rate after neutral salt-spray exposure. The Al–7Mg–4Zn–0.5Zr alloy achieved an ultimate tensile strength of 393.1 ± 2.0 MPa and an elongation of 10.1 ± 1.0%. These findings demonstrate that low-Sc alloying provides an effective strength–corrosion balance, while Zn/Zr modification offers a promising lower-cost strategy for reducing Sc dependence in high-performance L-DED Al–Mg alloys.