Effect of solidification structure on the microstructure and the mechanical properties of 7050 aluminum alloy sheet

Lightweight and high-strength 7xxx aluminum alloy has long been the preferred material in aircraft, high-speed railways, and other fields. In the present study, the influence of solidification structure on the microstructure and mechanical properties of aged sheets was investigated. To achieve this objective, firstly, ingots with different grain sizes, dendrite arm spacings, and crystalline phase sizes were prepared with different casting conditions. Then, the microstructure of the aged sheets was systematically characterized and the tensile properties were examined. The results indicate that the number density and area fraction of precipitates of sheets prepared by ingots with coarser grains, finer dendritic arms, and finer crystalline phases are greater than those prepared by ingots with finer grains, coarser dendritic arms, and coarser crystalline phases. As a result, the ultimate tensile strength, and the yield strength of the aged sheet prepared by ingots with coarser grains, finer dendritic arms, and finer crystalline phases are 38 MPa and 39 MPa higher than that of the aged sheet prepared by ingots with finer grains, coarser dendritic arms, and coarser crystalline phases. In addition, sheets produced using ingots with fine crystalline phases exhibited finer residual phases, which results in a better ductility of the sheet. Moreover, compared with the ingot grain size, the amount and size of residual coarse phases play a more important role in determining the grain size of the sheet.