Effect of solid solution heat treatment following age hardening on microstructure and mechanical properties of 7000 series power aluminum alloy

In this paper, Al-11.1Zn-2.7Mg-1.7Cu-1.4Ti-0.2Zr alloy material was prepared by powder metallurgy to study the effect of the different solid-solution aging systems on the microstructure and mechanical properties of this 7000 series aluminum alloy. The microstructure of the alloy under the three different solid-solution processes S1, S2, and S3 were observed using an optical microscope, scanning electron microscope, and X-ray diffraction analysis. The mechanical properties were tested to determine the best solid-solution process. The results show that under the S2 solid-solution process, the alloy has the best mechanical properties, with a compressive strength of 646.7(±6.5) MPa and a fracture strain of 5.9(±0.06)%. The maximum hardness trends in the three solid-solution processes after aging are S2>S3>S1. The maximum hardness 220.7(±5.5 )HV occurs after S2 solid-solution and 121℃×18 h aging. Moreover, after S2 solid-solution treatment, the solid-solution degree is close to saturation, the solid-solution strengthening effect is the best, and dislocations contribute the most to the strength.