There are 4 basic temper groupings for aluminium products:

"F" - as fabricated
Shaped by cold working, hot working or casting processes in which no special control over thermal processes or strain hardening is employed.

"O" - Dead soft (i.e. fully annealed)
Applies to wrought products that are annealed to obtain the lowest strength temper and to cast products tha t are annealed to improve ductility and dimensional stability. The "O" may be followed by a digit other than zero. Click for details about "O" condition

"T" - Heat treated (i.e. for age hardening alloys)
Applies to products that are thermally treatable (2000, 6000 and 7000 series), with or without supplementary strain-hardening, to produce stable tempers. The "T" is always followed by one or more digits. Click for details about "T1", "T3", "T4", "T5", T6", "T7" or "T8" conditions.

"H" - Strain hardened (i.e. for non age hardening alloys, wrought products only)
This temper applies to products that have their strength increased by strain hardening, with or without supplementary thermal treatment to produce some reduction in strength. The "H" is always followed by two or more digits:

The first digit following the H indicates the specific combination of basic operations and is comprised between 1 and 4:

• H1x: cold worked only.
  Applies to products that are strain-hardened to obtain the desired strength without supplementary thermal treatment.
• H2x: cold worked and partially annealed.
  Applies to products that are strain-hardened and then reduced in strength to the desired level by partial annealing.
• H3x: cold worked and stabilized.
  Applies to products that are strain-hardened and whose mechanical properties are stabilized, either by a low temperature thermal treatment or as a result of heat introduced during fabrication. Stabilization usually improves ductility.
• H4x: cold worked and lacquered or painted.
  Applies to products which are strain-hardened and which are subjected to some thermal operation during the subsequent painting or lacquering operation.

The second digit following the H indicates the degree of strain hardening (or cold work) as identified by the minimum value of the ultimate tensile strength and is comprised 1 and 9. The minimum tensile strength of tempers Hx8 is calculated from a table and is based on the minimum tensile strength of the alloy in the annealed temper (for more info please refer to European standard EN 515:1993).

Click for details about "Hx2", "Hx4", "Hx6", "Hx8" or "Hx9" conditions.