Some variations provide an aluminum alloy feedstock for additive manufacturing, the aluminum alloy feedstock comprising from 79.8 wt % to 88.3 wt % aluminum; from 1.1 wt % to 2.1 wt % copper; from 3.0 wt % to 4.6 wt % magnesium; from 7.1 wt % to 9.0 wt % zinc; and from 0.5 wt % to 2.8 wt % zirconium as a grain-refiner element. The aluminum alloy feedstock may be in the form of an ingot powder. In some variations, the aluminum alloy feedstock comprises from 81.3 wt % to about 87.8 wt % aluminum; from 1.2 wt % to 2.0 wt % copper; from 3.2 wt % to 4.4 wt % magnesium; from 7.3 wt % to 8.7 wt % zinc; and from 0.5 wt % to 2.8 wt % zirconium.