Laser metal deposition (LMD) of 7075 aluminum alloy with minimized defects: Process, microstructure and mechanical properties

The fabrication of structural-functional integrated large-size 7xxx aluminum (Al) alloy components via laser metal deposition (LMD) for industrial applications faces significant challenges, including high defect density and insufficient mechanical performance. In this study, to fabricate high-quality 7075 alloy, single-track deposition was first performed to evaluate the influence of process parameters on track morphology. Based on these results, single-layer deposition was subsequently conducted to investigate defect control strategies. The results indicated that the mass energy density and the linear powder feeding rate proposed in this work are key parameters determining the morphology of single-track deposits, while the overlap ratio directly affects the pore defects distribution in the single-layer island. Ultimately, by gaining a comprehensive understanding of the influence of LMD process parameters on single-track morphology and defect control, LMD-fabricated 7075 Al block parts with a porosity as low as 0.34 % were successfully produced. The mechanical test results showed that, the ultimate tensile strength (UTS) and elongation (EL) of the 7075 Al with low porosity were 206.2 ± 22.7 MPa and 3.99 ± 0.44 %, respectively, which were markedly higher than those of the previously reported LMD-fabricated 7075 alloy with high pore defect density. The excellent mechanical performance was attribute to the significantly reduced defect density and fine Al₂MgCu precipitates. This study offers valuable insights for accelerating the LMD process in the fabrication of high-quality 7075 alloy components, thereby meeting the demands of engineering applications.