1. Alloy series and typical grades
2xxx series (Al-Cu-Mg): Typical grades: 2024-T3, 2014-T6, which are hard aluminum alloys. After solution treatment and aging strengthening, the tensile strength can reach 450-500MPa. Application: 2024 bending aluminum flat bar can be used for aviation structural parts (such as aircraft skins and frames) and high-load mechanical parts. 6xxx series (Al-Mg-Si): Typical grades: 6061-T6, 6069-T6, which are forged aluminum alloys. The combination of Mg-Si elements can significantly improve the ductility and strength after heat treatment (such as 6069-T6 is 40% stronger than 6061). Application: 6061 aluminum sheets can be used for automobile body structures, building profiles and ship components. 7xxx series (Al-Zn-Mg-Cu):
Typical grades: 7075-T6, 7050-T74, super-hard aluminum alloy, room temperature strength can reach more than 570MPa, but high temperature environment should be avoided to prevent stress corrosion15.
Application: 7075 aluminum profile is suitable for aerospace load-bearing parts (such as landing gear, wing beam) and military equipment.
2. Core process of heat treatment process Solution treatment:
Heat the alloy to 480-520℃ (adjusted according to the grade) to dissolve the strengthening phase in the aluminum matrix, and then quickly cool (water quenching) to form a supersaturated solid solution.
Aging:
Natural aging: Heat treatable aluminum alloy is placed at room temperature for several days (such as T4 state), which is suitable for some 2xxx series aluminum alloys.
Artificial aging: Heating to 120-200℃ and keeping warm (such as T6 state) promotes precipitation of strengthening phases (such as Mg₂Si, Al₂Cu) to improve hardness and strength.
3. Performance advantages and limitations Advantages :
High strength-to-weight ratio, 7075-T6 density is only 2.8g/cm³, and the strength is comparable to that of steel.
Corrosion resistance can be enhanced by anodizing or coating (such as 5083 marine alloy).
Limitations :
Alloys with high zinc content (such as 7xxx series) are prone to stress corrosion cracking (SCC), and environmental humidity and Cl⁻ concentration need to be strictly controlled.
Some alloys (such as the copper-containing 2xxx series) have poor welding performance and require special processes.
