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What does the “T” temper designation mean (e.g., T5, T6)?

    The “T” temper designation indicates the thermal treatment (aging) the aluminum has undergone to achieve specific mechanical properties.

    • T5: Cooled from the extrusion process with forced air (a form of quenching) and then artificially aged. This is the most common temper for extruded profiles. It provides a good balance of strength and is economical.
    • T6: Solution heat-treated (heated to a high temperature and quenched in water) and then artificially aged. This yields the highest strength and hardness for the alloy but can cause more distortion and is slightly more expensive. Often used for high-stress components like from 6061.
    • Other Tempers: T4 (solution heat-treated, naturally aged), T52 (stress-relieved by stretching), etc. The choice affects yield strength, tensile strength, and elongation.