Atom probe tomographic study of elemental segregation at grain boundaries for a peak-aged Al–Zn–Mg alloy

• Atom probe tomography is used to characterize the solute segregation at GBs.
• Mg segregates at GBs within 3 nm for a peak-aged Al–Zn–Mg alloy.
• Zn does not segregate at GBs.
• MgZn2 precipitates are not the H trapping sites, but Mg2Si precipitates are.
• Clusters containing Zn, H and oxides have been found at GBs.

Atom probe tomography (APT) has been used to characterize the element segregation at the grain boundary (GB) for a peak-aged Al–Zn–Mg alloy with high stress corrosion cracking (SCC) susceptibility. The results show that Mg segregates along the GB with a peak concentration of 1.38 at.% and width of 3 nm. Zn does not segregate at GB. However, segregation of Zn and H atoms at oxide-containing clusters on GB has been observed. APT atom maps also reveal that Mg2Si is the H trapping site, but MgZn2 is not.