Unraveling the effect of dislocations and deformation-induced boundaries on environmental hydrogen embrittlement behavior of a cold-rolled Al–Zn–Mg–Cu alloy

The effect of dislocation substructure, and deformation-induced boundaries on the hydrogen embrittlement (HE) behavior and the fracture mechanism of a 7xxx series aluminum alloy was investigated using X-ray diffraction line-profile analysis, electron backscatter diffraction, transmission electron microscopy, thermal desorption spectroscopy, and visualization of hydrogen. Hydrogen resides at interstitial lattice sites, statistically-stored dislocations (SSDs), and high-angle boundaries (HABs). SSDs are not the main trap site affecting HE behavior of the alloy. However, the HABs with the high desorption energy act as an almost irreversible trap site, which strongly absorbs hydrogen. It was firstly reported that the higher density of HABs as a strong trap site in a deformed 7xxx series aluminum alloy leads to decreasing the possibility of building up a critical hydrogen concentration required for crack initiation in a typical HAB, resulting in an excellent hydrogen embrittlement resistance.