The main characteristics of aluminum alloys for aerospace are: large-scale and integration, thin-walled and lightweight, precision of section size and geometric tolerance, uniformity and quality of microstructure and properties. According to different service conditions and parts of aircraft, aluminum alloys for aerospace are mainly high-strength aluminum alloy, heat-resistant aluminium alloy and corrosion-resistant aluminum alloy. High strength aluminum alloy is mainly used for aircraft fuselage components, engine compartment, seats, control systems, etc., and is the most widely used,For example, 5086 aluminum alloy.
The biggest characteristic of aviation aluminum alloy is that it can improve the strength by deformation heat treatment. Deformation heat treatment is a comprehensive process that combines the deformation strengthening of plastic deformation with the phase transformation strengthening during heat treatment to unify the forming process and formability. During the plastic deformation process of aviation aluminum alloy, the defect density inside the crystal increases, and these crystal defects will cause the change of the internal microstructure of the material. In the process of plastic deformation of aviation aluminum alloy, dynamic recovery, dynamic recrystallization, sub dynamic crystallization, static recrystallization, static recovery and other crystal structure changes will occur. These changes in crystal structure, if properly controlled, will significantly improve the mechanical properties of the material and enhance the service life of the material.
Aeronautical aluminum alloys are generally strengthened by precipitation of dispersed phase in supersaturated solid solution. The general precipitation sequence is: segregation region (or GP region) ~ transition phase (metastable phase) ~ equilibrium phase. In the process of deformation heat treatment, deformation induces precipitation, precipitation affects deformation, deformation and precipitation affect each other, and dynamically affect the properties of the material.
The precipitation strengthening process of deformation heat treatment is greatly affected by temperature. Deformation heat treatment can be divided into high temperature deformation heat treatment and low temperature deformation heat treatment. The basic processes of low temperature deformation heat treatment are: quenching of aviation aluminum alloy, cold deformation at room temperature and aging heat treatment. After this treatment, the strength of aviation aluminum alloy is greatly improved, but the plasticity is reduced. High temperature deformation heat treatment process: quenching, high temperature deformation and aging. After high temperature deformation heat treatment, the strength of the material is higher, the plasticity and toughness are improved, and the heat resistance strength of the alloy is also improved.