Effect of Mg + Si content on the mechanical properties and intergranular corrosion behaviors of Al–Mg–Si alloys

In this study, the influence of the Mg + Si content on the microstructure features, mechanical properties, and intergranular corrosion (IGC) behaviors of T6-aged Al-Mg-Si alloys was investigated. In the present work, the detrimental effect of grain boundary phase formation induced by high total solute content (Mg + Si) on the mechanical and IGC properties of the alloy was identified. A lower solute content formed slightly low-density and fine second-phase particles, due to a moderate nucleation drive. The reduced particle number and size resulted in a marked increase in ductility and a marginal reduction in strength. It is noteworthy that the precipitation of continuous Mg 2 Si and Si-rich phases at grain boundaries is considerably inhibited by the decreased solute supply. Through this effect, along with a narrow precipitation-free zone (PFZ) and a high proportion of low-angle grain boundaries, IGC propagation is effectively disrupted. Thus, an alloy exhibiting an optimal combination of excellent IGC resistance, high ductility, and high cost-effectiveness was identified.