Grain boundary structures and their correlation with intergranular corrosion in an extruded Al-Mg-Si-Cu alloy

A detailed analysis of grain boundaries in a highly textured Al-Mg-Si-Cu alloy is presented in this work. Electron backscatter diffraction demonstrates the presence of three main categories of grain boundaries in addition to sub-grain boundaries. These grain boundaries have been systematically analysed using high–resolution scanning transmission electron microscopy. Intergranular corrosion (IGC) susceptibility was statistically correlated with the same defined grain boundaries. A high density of metastable Q′-phase grain boundary particles correlates with a reduction in Cu segregation at grain boundaries and increased IGC resistance. Results herein are relevant in further understanding grain boundary structures in Al-Mg-Si-Cu alloys and their susceptibility to IGC, and can be implemented into modelling frameworks.