Effect of Second Step Aging on Microstructure and Properties of 7050 Aluminum Alloy Thick Plate

The influence of the second step aging treatment on tensile properties, fracture toughness and electrical conductivity of 7050 aluminum alloy thick plates was investigated. Meanwhile, the strengthening-toughening mechanism was analyzed by transmission electron microscopy and scanning electron microscopy. The results show that the sizes and distance of precipitates phases increased and the strength of the alloy decreased, the fracture toughness and the stress corrosion resistance increased, the dimple character in shearing and transgranular dimple mixed fracture was more outstanding, and the effect of aging temperature on the alloy properties was more obvious than aging time with the second aging temperature or time increasing when the first step aging conditions was same. The alloy had good comprehensive properties after aging at 120 ℃ for 4 h and 165 ℃ for 28 h.