Effects of Si Content on Microstructure and Mechanical Properties of 8079 Aluminum Alloy

Because of high strength and low breaking rate, 8079 aluminum alloy has become the main material of double zero aluminum foil. However, there are still many problems in the manufacturing process, such as broken belt, pinhole and so on. As the main influencing element, Si has a great influence on the alloy. In this work, the influences of Si with various contents on microstructural evolution and mechanical properties of 8079 aluminum alloy were analyzed by energy dispersive spectrometer (EDS), optical microscope (OM), X-Ray diffraction analyzer (XRD), universal testing machine and Vickers hardness tester. The results showed that the primary Si phase was tiny and dispersed in the alloy when the content of Si is less than 1.3%. As the second phases dispersion strengthening, the Si phase can improve the strength of the alloy. However, when the Si content was too high, the Si phase increased and coarsened. Meanwhile, Fe-rich phase which increased by Si decreased the fine grain strengthening and the second phases strengthening mechanism. The coarse Si phase and the Fe-rich phase are brittle phase, which are easy to become the crack source in the process of material deformation and reduce the strength and toughness of the alloy. The mechanical property test shows that the performance of 8079 aluminum alloy is the best when the Si content is 1.3%.