The addition of 3 wt-% Zn to the traditional Al–Mg alloy doubled its strength. To understand the strengthening mechanism, the enhancement in strength with the variation in Mg content was studied. The grain boundary and solid solution strengthening decrease with the reduction in the Mg content; however, their contributions to the yield strength are insignificant. The contribution of precipitation strengthening to the yield strength is more than 80%; however, due to the unchanged precipitate characteristics, the strengthening effect changes slightly with the variation in the Mg content. The reduction in strength is primarily due to Mg solid solution strengthening. The variation in the ductility of Al–Mg–Zn alloys was studied by fracture analysis.

The higher hot cracking tendency during fusion welding in traditional high-strength 7000 series alloys has been an obstacle for its further application. In this study, the cracking susceptibility can be suppressed by fabricating Al–Mg–Zn–Cu alloys with Zn/Mg≤1 and Cu/Mg≤0.25 while simultaneously maintaining the high strength. A T-shaped device combined with non-equilibrium solidification is developed to simulate the solidification during fusion welding, and it is effective to predict the shrinkage load, temperature and solid fraction. The effect of solidification temperature range, the amount of eutectics at the terminal stage of solidification and the shrinkage load during solidification on the hot cracking susceptibility are discussed in detail.