Wrought and cast aluminium alloys use different identification systems. Wrought aluminium is identified with a four digit number which identifies the alloying elements. Cast aluminium alloys use a four to five digit number with a decimal point. The digit in the hundreds place indicates the alloying elements, while the digit after the decimal point indicates the form (cast shape or ingot). The temper designation follows the cast or wrought designation number with a dash, a letter, and potentially a one to three digit number, e.g. 6061-T6. The definitions for the tempers are:[5][6] -F -H As fabricated Strain hardened (cold worked) with or without thermal treatment -H1 Strain hardened without thermal treatment -H2 Strain hardened and partially annealed -H3 Strain hardened and stabilized by low temperature heating Second digit A second digit denotes the degree of hardness -HX2 = 1/4 hard -HX4 = 1/2 hard -HX6 = 3/4 hard -HX8 = full hard -HX9 = extra hard -O -T Full soft (annealed) Heat treated to produce stable tempers -T1 Cooled from hot working and naturally aged (at room temperature) -T2 Cooled from hot working, cold-worked, and naturally aged -T3 Solution heat treated and cold worked -T4 Solution heat treated and naturally aged -T5 Cooled from hot working and artificially aged (at elevated temperature) -T51 Stress relieved by stretching -T510 No further straightening after stretching -T511 Minor straightening after stretching -T52 Stress relieved by thermal treatment -T6 Solution heat treated and artificially aged -T7 Solution heat treated and stabilized -T8 Solution heat treated, cold worked, and artificially aged -T9 Solution heat treated, artificially aged, and cold worked -T10 Cooled from hot working, cold-worked, and artificially aged Solution heat treated only
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