Investigating the role of Cu, Zr and V on the evolution of microstructure and properties of Al-Si-Mg cast alloys

Understanding the evolution of as-cast microstructure (especially eutectic Si and intermetallics) in Al-Si-Mg alloys is critical for improving the mechanical properties because they could be beneficial or detrimental depending on their size, morphology, and distribution. In this study, the effects of transition metal elements Cu, Zr, and V on the microstructure and mechanical properties of Al-Si-Mg cast alloys were investigated. It was found that the addition of Cu reduced the secondary dendrite arm spacing (SDAS) and led to the formation of coarse Si particles. However, SDAS was further refined when Zr and V were added. The yield tensile strength and ultimate tensile strength of Al-Si-Mg cast alloy was increased when Cu was added due to the solid solution and the decrease of SDAS, while additions of Zr and V led to the significant reduction in ductility and ultimate tensile strength of the Al-Si-Cu-Mg alloy due to the needle-shaped phases (Zr-Ti-V-containing phase). Such particles promoted stress concentration, leading to early fracture and reduced ductility.