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Temper Designation System for Non-heat Treatable Al Alloys

Strain hardening is a natural consequence of most working and forming operations on aluminium and its alloys. In pure aluminium and the non-heat-treatable aluminium-manganese and aluminium-magnesium alloys, strain hardening increases the strengths achieved through solid solution and dispersion hardening...

Strain hardening is a natural consequence of most working and forming operations on aluminium and its alloys. In pure aluminium and the non-heat-treatable aluminium-manganese and aluminium-magnesium alloys, strain hardening increases the strengths achieved through solid solution and dispersion hardening.

Work hardening is used extensively to produce strain hardened tempers of the non-heat-treatable alloys. The temper designation system, according to ANSI H35.1(M), is shown bellow.

F As-fabricated. Applies to the product of shaping processes in which no special control over thermal conditions or strain-hardening is employed. For wrought products, there are no mechanical property limits.
O Annealed. Applies to wrought products which are annealed to obtain the lowest strength temper, and to cast products which are annealed to improve ductility and dimensional stability. The O may be followed by a digit other then zero.
H Strain hardened (wrought products only). Applies to products which have their strength increased by strain hardening, with or without supplementary thermal treatments 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, as follows:

H1 Strain hardened only. Applies to products which are strain – hardened to obtain the desired strength without supplementary thermal treatment. The number following this designation indicates the degree of strain hardening.
H2 Strain hardened and partially annealed. Applies to products which are strain – hardened more than the desired final amount and then reduced in strength to the desired level by partial annealing. For alloys that age-soften at room temperature, the H2 tempers have the same minimum ultimate tensile strength as the corresponding H3 tempers. For other alloys, the H2 tempers have the same minimum ultimate tensile strength as the corresponding H1 tempers and slightly higher elongation. The number following this designation indicates the degree of strain – hardening remaining after the product has been partially annealed.
H3 Strain hardened and stabilized. Applies to products which are strain – hardened and whose mechanical properties are stabilized either by a low temperature thermal treatment or as a result of a heat introduced during fabrication. Stabilization usually improves ductility. This designation is applicable only to those alloys which, unless stabilized, gradually age-soften at room temperature. The number following this designation indicates the degree of strain-hardening remaining after the stabilization treatment.

The digit following the designations H1, H2 and H3 indicates the degree of strain hardening.

Numeral 8 has been assigned to indicate tempers having an ultimate tensile strength equivalent to that achieved by a cold reduction (temperature during reduction not to exceed 50oC) of approximately 75 percent following a full anneal.

Tempers between O (annealed) and 8 are designated by numerals 1 through 7. Material having an ultimate tensile strength about midway between that of the O temper and that of the 8 temper is designated by the numeral 4; about midway between the O and 4 tempers by the numeral 2; and about midway between 4 and 8 tempers by the numeral 6.

Numeral 9 designates tempers whose minimum ultimate tensile strength exceeds that of the 8 temper by 10 MPa or more. For two–digit H tempers whose second digit is odd, the standard limits for strength are the arithmetic mean, rounded to the nearest multiple of 5 MPa of the standard limits for the adjacent two digit H tempers whose second digit are seven.

The third digit, when used, indicates a variation of a two–digit temper. It is used when the degree of control of temper or the mechanical properties or both differ from, but are close to, that (or those) for the two–digit H temper designation to which it is added, or when some other characteristic is significantly affected.

February, 2001
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