Microstructure and aging behavior of spay-formed Al-Zn-Mg-Cu alloys were investigated as a function of alloying element addition. It reveals that the grains of the as-deposited alloys are refined with increasing Zn element, while the function of the Ni addition is to reduce grain boundary particles and eutectic in the as-extruded condition. Particles containing Mg and Zn are found to be increased with Zn content increasing, while the role of Ni is to reduce both number and size of these particles. During artificial aging, the increment of Zn content produces not much effect on peak hardness, in addition to an accelerated overage softening. An addition of about 0.13% Ni, however, gives rise to not only an improved peak hardness but also an improvement of property stability at the aging temperature.
