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The microstructure and mechanical properties of Al–Cu–Mg–(Ag)–Mn–Zr alloys were studied by means of tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that small additions of Ag to Al–Cu–Mg–Mn–Zr alloy can accelerate the hardening effect of the aged alloy and reduce the time to peak-aged. The mechanical properties can be improved both at room temperature and at elevated temperatures, which is attributed to the fine and uniform plate-like Ω precipitates. Meanwhile the ductility of the studied alloys remains at relatively high level. The major strengthening phases of the Ag-free alloy are θ ′ and less S ′, while that of Al–Cu–Mg–Mn–Zr alloy containing trace amounts of Ag are Ω and less θ ′.

Five kinds of Al-Zn-Mg-Cu-Zr based alloys with different Sc additions were prepared by ingot metallurgy. The effects of minor Sc on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Zr based alloys were investigated using tensile tests, optical microscopy (OM), and transmission electron microscopy (TEM). The results show that the ultimate tensile strength and yield strength are improved by 94 and 110 MPa, respectively, and the elongation to failure remains at a reasonable extent (11.1%) in the Al-Zn-Mg-Cu-Zr based alloy with 0.21 wt.% Sc addition after solution heat treatment at 475°C for 40 min and then aged at 120°C for 24 h. The addition of minor Sc induces the formation of Al3(Sc,Zr) particles, which are highly effective in refining the cast microstructures, retarding recrystallization, and pinning dislocations. The increment of strength is attributed mainly to fine grain strengthening, precipitation strengthening of Al3(Sc,Zr) particles, and substructure strengthening.

The flow behavior of Al–Cu–Mg–Ag alloy and its microstructural evolution during hot compression deformation were studied by thermal simulation test. The flow stress increased with increasing the strain rate, and decreased with increasing the deforming temperature, which can be described by a constitutive equation in hyperbolic sine function with the hot deformation activation energy 196.27 kJ/mol, and can also be described by a Zener–Hollomon parameter. The dynamic recrystallization only occurred at low Z values, which must be below or equal to a constant of 5.31 × 10 13 s −1 . With decreasing Z value, the elongated grains coarsed and the tendency of dynamic recrystallization enhanced. Correspondingly, the subgrain size increased and the dislocation density decreased. And the main soften mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization.

The effects of aging on the microstructure, mechanical properties, intergranular corrosion, and exfoliation corrosion of an Al-3.5Cu-1.5Li-0.22(Sc+Zr) alloy have been investigated. The results show that the alloy has the character of age hardening, and the major phase of precipitation and strengthening is the T1 phase. The aging temperature and aging time have a significant effect on the amount and distribution of the T1 phase. The proper artificial single-aging treatment of the alloy is at 160r°C for 40 h. The intergranular corrosion and exfoliation corrosion of the alloy are caused by the anodic dissolution of the T1 phase and the precipitate-free zone (PFZ). With increasing the aging time to overaged, the T1 phase coarsens, and the PFZ widens, leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion.

Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc, Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 °C/h solution and 120 °C/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.

We melted five types of Al-Zn-Cu-Mg-Zr alloys and added 0.0, 0.1, 0.2, 0.3, and 0.5 (wt.%) of scandium. Its influence on the microstructure of alloys and their mechanical properties is studied with the help of optical transmission and scanning electron microscopes. An insignificant amount of scandium promoted the formation of Al3 (Sc, Zr) particles. These particles efficiently clean the microstructure, decelerate and preserve recrystallization, and fix dislocations and substructures. The strength of the alloys increases for high levels of plasticity. It is shown that the optimal properties of the alloys with 0.21% Sc are attained after holding in a solution for 40 min at 475°C and aging for 24 h at 120°C. The strength of the alloys increases mainly as a result of dispersion solidification and microstructural hardening with Al3 (Sc, Zr) particles.