What is the purpose of heat treatment for aluminum alloys?

Heat treatment strengthens precipitation-hardenable aluminum alloys. Process: Solution heat treatment - Heat to dissolve alloying elements into solid solution (~480-530C for 7xxx), hold time for dissolution; Quench - Rapid cooling (water, polymer) to retain supersaturated solution; Aging - Natural aging (room temperature, -T4) or artificial aging (elevated temperature, -T6) precipitates strengthening phases. Effects: Strength increases significantly (2024-T3: 70 ksi vs 2024-O: 27 ksi), Hardness increases, and Ductility typically decreases. Common tempers: -T3: Solution treated, cold worked, naturally aged; -T6: Solution treated, artificially aged (maximum strength); -T7: Overaged (lower strength, better stress corrosion resistance). Proper heat treatment is critical; improper quench rate or aging can dramatically reduce properties. Documentation and process control essential for aerospace quality.