Ab initio calculation of the tensile deformation of Al–Zn–Mg alloy models was performed to clarify the mechanism for hydrogen embrittlement in the Al–Zn–Mg alloy. The atomistic models of Al/MgZn₂ boundaries containing a hydrogen atom, which the authors obtained previously, were used as the initial stable structures with hydrogen segregated at η1, η2, η4 interfaces (notation used by J. Gjønnes and Chr. J. Simensen). The models were strained uniaxially at a constant rate and their total energies after the structural relaxation were calculated by the ab initio method. It has been found that the hydrogen atom trapped near the Al matrix/MgZn₂ precipitate interface deteriorates the strength of the Al–Zn–Mg alloys by weakening the bonding strength between Al and Mg–Zn. The authors have proposed that the interface strength can be estimated by the maximum of the derivative of the cohesive energy per unit area and have found that η4 shows the highest strength under tensile deformation. The proposed criteria can be applied to estimate the interface strength of various materials.

Corrosion resistant films were fabricated on Al–Zn–Mg alloy by steam coating using Zn(NO₃)₂ aqueous solution at different concentrations. XRD patterns and FT-IR spectra demonstrated that nitrate type Zn–Al layered double hydroxide (LDH) and ZnO films were formed on the Al–Zn–Mg alloys by steam coating at the temperatures of 373 to 433 and 473 K, respectively, using Zn(NO₃)₂ aqueous solution at 1000 mM. γ-AlO(OH) films were found to be prepared on the Al–Zn–Mg alloys by steam coating at 513 K using Zn(NO₃)₂ aqueous solutions at the concentrations of 1 to 100 mM. The corrosion resistance of the films was investigated by potentiodynamic polarization curve measurements. The polarization curve measurements revealed that the γ-AlO(OH) films prepared by steam coating at 513 K using 1 mM of Zn(NO₃)₂ aqueous solution was most effective to suppress pitting corrosion and anodic current density.

Dislocation multiplication and dynamic recovery in the tensile deformed Al–Mg–Si–Cu alloys were characterized by transmission electron microscope (TEM), to reveal the correlation between the dislocation characteristics and the elongation behaviors. 6016 (Al–0.4%Mg–1.0%Si–0.2%Cu (mass%)) and 6014 (Al–0.6%Mg–0.7%Si–0.1%Cu) alloys were aged at 363 K for 18 ks after solution treated and quenched into water. The maximum n-value of 6016 alloy was found higher than that in the 6014 alloy. The n-value reduction rate after reaching its maximum of 6016 alloy was found smaller than that of 6014 alloy. Furthermore, the dislocation multiplication on {111} plane and the formation of dislocation band were formed in 6016 alloy with more than 10% of tensile deformation. Therefore, the slip lines observed by scanning electron microscope (SEM) are finely formed. The homogeneous dispersion of slip lines are probably the cause of higher elongation of 6016 alloy than that of 6014 alloy. It is believed that suppression of the cross slip dislocation may contribute to a higher elongation.