Effect of Fe and Si Content on Microstructure, Mechanical Properties, and Corrosion Resistance of 7050 Alloy

In this work, the effect of Fe and Si content on microstructure, mechanical properties, and corrosion resistance of 7050 alloy was systematically investigated by room temperature tensile, fracture toughness, and exfoliation corrosion tests, complemented by microstructural characterization through SEM and TEM. The results demonstrate that the impurity elements Fe and Si induce the formation of insoluble Fe-rich phases and Mg₂Si phases in the alloy, respectively. The coexistence of Fe and Si leads to a severe synergistic deterioration effect on mechanical properties. Furthermore, the study reveals that Si has a more profound negative impact on mechanical properties than Fe. While Fe primarily reduces ductility and fracture toughness by initiating microcracks through Fe-rich phases with minimal effect on strength, Si not only forms brittle Mg₂Si phases that impair toughness but also significantly depletes the Mg content in the matrix, thereby reducing the quantity of strengthening phases. This results in a comprehensive and severe decline in strength, plasticity, and toughness. In addition, Fe and Si impurities markedly degrade the exfoliation corrosion resistance of the alloy.