7000 series aluminium alloys are mainly strengthened by solution treatment and artificial aging. The room temperature tensile strength is mostly between 460 MPa and 630 MPa. The stress corrosion resistance, fatigue property, fracture toughness and other comprehensive properties of the alloy are also significantly affected by different heat treatment conditions. The basic heat treatment states of 7000 series aluminium alloys are O, T6, T73, T76 and T77. Compared with other states, the semi-finished products in T6 state have the highest tensile strength, but the properties of stress corrosion resistance, fracture toughness and notch sensitivity are relatively poor. Compared with T6 state, the stress corrosion resistance and fracture toughness of T73 state are significantly improved, but the strength decreases by about 12%. Compared with the T6 state, the T76 state improves the corrosion resistance, especially the spalling corrosion resistance and fracture toughness, but the tensile strength decreases by about 5%. The stress corrosion resistance and tensile strength of T74 are between those of T73 and T76. The strength of T77 state reached the level of T6 state, while the corrosion resistance reached the level of T76 state.
With the development of alloy composition design, solution treatment and artificial aging technology, the properties of
7000 series aluminium alloys are continuously optimized, and the types and varieties of alloys are becoming more and more perfect. They are widely used in skin, partition, sorghum, girder, wing ribs, joints, pillars and landing gear, and other key boards and important parts of airframe.
