FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesMedium
A technician must form a complex compound bend in a 2024 aluminum bracket without cracking, and plans to heat-treat the part to the required strength after fabrication is complete. Which temper condition should the raw stock be in prior to forming?
- A2024-T3
- B2024-T6
- C2024-T4
- D2024-O
Show answer & explanationAnswer & explanation
Correct answer: D. 2024-O
The 'O' temper is fully annealed, giving 2024 aluminum its softest and most ductile state for severe forming operations. After forming, the part can be heat-treated (solution treated and aged) to develop the required T-condition strength.
Why the other options are wrong
- A. T3 is solution heat-treated and strain-hardened, too hard for severe forming.
- B. T6 is fully heat-treated to maximum strength, brittle for complex bends.
- C. T4 is solution heat-treated and naturally aged, less workable than annealed stock.
Aluminum O Temper
The fully annealed condition of aluminum alloy, providing maximum ductility for forming operations before subsequent heat treatment.
- O = annealed, softest condition
- Used for severe forming before heat treatment
- T-tempers (T3, T4, T6) are stronger but less ductile
Memory trick: 'O' is Open and soft — bend it before you bake it hard