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.

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.

The first digit following the H indicates the specific combination of basic operations, as follows:

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.