What is the alloy number of the most commonly used aluminum alloy for aircraft structural use?

• A. 2024-T
• B. 6061-T6
• C. 7075-T6
• D. 2017-T4

Answer: (A)

6061-T6 is the alloy most commonly used for aircraft structure because it offers a balanced combination of properties that engineers rely on for everyday fabrication. The 6xxx series (aluminum-magnesium-silicon) can be heat-treated to a solid strength level while maintaining excellent corrosion resistance, good formability, and very good weldability. It comes in sheet, plate, and extrusion forms, making it versatile for skins, frames, ribs, brackets, and other structural members, and it’s generally cost-effective and readily available.

The other alloys have their uses but don’t match the overall practicality for broad structural use. The 2024 alloy is very strong but has poorer corrosion resistance and more demanding processing requirements. The 7075 alloy is even stronger but offers limited weldability and corrosion resistance, making it less suitable for general structural work. The 2017 alloy is favored for machinability rather than structural performance.