| dc.description.abstract | This study used microstructure observation, differential scanning calorimetry, corrosion properties and mechanical property (exfoliation corrosion, polarization corrosion, and stress corrosion resistance) tests, etc., to discuss the effects of Cu content (1.2, 1.9 wt%) and enhanced solution treatment (EST) on mechanical properties and corrosion resistance of Al-9.0Zn-2.3Mg-xCu-0.05Zr high-strength forging aluminum alloy. The results showed that the strength of the alloy increased significantly with the increasing of Cu content, which led to a decrease in the corrosion potential of the alloy, thus impairing the corrosion resistance of the alloy. However, the alloy with low Cu content reduced the strength of the alloy due to the decrease in the precipitation of the η′-MgZn2 phase (and η-MgZn2 phase), but it could effectively reduce the residual S-Al2CuMg phase. Therefore, the alloy′s corrosion resistance was improved.
In addition, compared with the single-stage solution treatment (SST), the alloy subjected to the enhanced solution treatment (EST) could not only increase the precipitation power and the precipitation of η′-MgZn2 phase (and η-MgZn2 phase) to strengthen the alloy, but also significantly reduce the S-Al2CuMg phase. The Cu concentration of the η-MgZn2 phase on the boundary was also greatly increased, which further increased the corrosion potential around the alloy grain boundary, so that the alloy had better stress corrosion resistance.
Based on the above experimental results, it was found that Al-9Zn-2.3Mg-xCu-0.05Zr alloy with high Cu content (1.9 wt%) treated with the enhanced solution treatment could obtain the best mechanical properties and good corrosion resistance. Moreover, the solid solution temperature and hot working temperature of the alloy could also increase without overheating, which would help to increase the alloy hot working rate. | en_US |