FAA Aviation Mechanic Airframe (AMA)Airframe StructuresHard
A technician needs to anneal a work-hardened 2024 aluminum alloy sheet to soften it for extensive forming operations. Which process is correct?
- AHeat to approximately 250°F for a precipitation heat treatment cycle
- BHeat to approximately 950°F and immediately air cool
- CHeat to approximately 500°F and quench rapidly in cold water
- DHeat to approximately 775°F, hold at temperature, then cool slowly at a controlled rate
Show answer & explanationAnswer & explanation
Correct answer: D. Heat to approximately 775°F, hold at temperature, then cool slowly at a controlled rate
Annealing aluminum alloys such as 2024 involves heating to approximately 775°F (413°C), holding at that temperature, and then cooling slowly (typically furnace cooling at a controlled rate) to fully soften the material for forming. Rapid quenching would instead produce a solution heat-treated (hardened) condition, not an annealed one.
Why the other options are wrong
- A. 250°F is characteristic of a precipitation (aging) heat treatment, which hardens rather than softens the alloy.
- B. 950°F is far too high and would risk burning the aluminum alloy.
- C. Rapid water quenching is used for solution heat treatment (hardening), not annealing.
Annealing of Aluminum Alloys
A heat treatment process that softens work-hardened aluminum alloys by heating to approximately 775°F, holding, then slow cooling, restoring maximum workability.
- 2024 aluminum annealing temp ≈ 775°F (413°C)
- Slow controlled cooling (furnace cool) required
- Fully softens metal for extensive forming
- Opposite of solution heat treatment, which quenches rapidly to harden
Memory trick: Anneal is slow like a turtle — heat gently, cool gently.