Aluminum Alloys, Tempers and Terminology

Wrought Aluminum and Aluminum Alloy Designation System     A system for designating wrought aluminum and wrought aluminum alloys was established by the Aluminum Association. Specific limits for chemical composition to which conformance is required are provided by applicable product standards.     A system of four-digit numerical designations is used to identify wrought aluminum and wrought aluminum alloys. The first digit indicates the alloy group as follows: 1XXX Aluminum, 99.00% minimum and greater Pure Aluminum      In the 1XXX group for minimum aluminum purities of 99.00 percent and greater, the last two of the four digits in the designation indicate the minimum aluminum percentage. These digits are the same as the last two digits to the right of the decimal point in the minimum aluminum percentage when it is expressed to the nearest 0.01 percent. The second digit in the designation indicates modifications in impurity limits. If the second digit is zero, it indicates unalloyed aluminum having natural impurity limits; integers 1 through 9, which are assigned consecutively as needed, indicate special control of the of more individual impurities or alloying elements. Aluminum alloys grouped by major alloying elements 2XXX Copper (Cu). 3XXX Manganese (Mn) 4XXX Silicon (Si) 5XXX Magnesium (Mg) 6XXX Magnesium and Silicon (Mg and Si) 7XXX Zinc (Zn) 8XXX Other elements 9XXX Unused series Aluminum Alloys      In the 2XXX through 8XXX alloy groups the last two of the four digits in the designation have no special significance but serve only to identify the different aluminum alloys in group. The second digit in the alloy designation indicates alloy modifications. If the second digit is zero, it indicates the original alloy; integers 1 through 9, which are assigned consecutively, indicate alloy modifications. Temper Designation System      The temper designation system is used for all forms of wrought and cast aluminum and aluminum alloys except ingot. It is based on the sequence of basic treatments used to produce various tempers. The temper designation follows the alloy designation with the two separated by a hyphen. Basic designations consist of a letter while subdivisions of those basic tempers, where required, are indicated by one or more digits following those letters. The system is designed to set down specific sequences of fabrication processes, but only those operations that are recognized as significantly influencing the characteristics of the product involved. Should some other variation of the same sequence of basic operations be applied to the same alloy, resulting in different characteristics, the additional digits will be added to the numerical designation. Basic Temper Designations F As fabricated. Denotes metal that has been fabricated to ordered dimensions without any attempt on the part of the producer to control the results of either strain-hardening operations or thermal treatments. There are no mechanical property limits, and the strength levels may vary form lot to lot and from shipment to shipment. O Annealed. Applies to wrought products that have undergone a thermal treatment to reduce their mechanical property levels to their minimums. Often described as "dead soft" metal. W Solution heat-treated. An unstable temper applying to certain of the (7XXX) heat-treatable alloys that, after heat treatment, spontaneously age harden at room temperature. Only when the period of natural aging is indicated (W 1hr. for example) is this a specific and complete designation. H Strain-hardened. Applies to those wrought products which have had an increase in strength by reduction through strain-hardening or cold working operations. The "H" is always followed by two or more digits. T Thermally treated to produce tempers other than F, O or H. Applies to those products which have had an increase in strength due to thermal treatments, with or without supplementary strain-hardening operations. The "T" is always followed by one or more digits. Subdivisions of "T" Temper-Heat-Treatable Alloys T1 cooled from an elevated temperature shaping process and naturally aged to a substantially stable condition. Usually associated with extruded products and limited to the 6XXX series alloys. T2 cooled from an elevated temperature shaping process, cold worked, and naturally aged to a substantially stable condition. Usually associated with cast products. T3 solution heat-treated, cold worked, and naturally aged to a substantially stable condition. (T4+cold work) T4 solution heat-treated, and naturally aged to a substantially stable condition. T5 cooled from an elevated temperature shaping process and artificially aged. Usually associated with extruded products in the 6XXX series alloys. (T1+artificial age) T6 solution heat-treated, and artificially aged. (T4+artificial age) T7 solution heat-treated, and overaged/stabilized. Applies to alloy products which are thermally overaged after solution heat-treatment to carry them beyond the point of maximum strength to provide control of some special characteristic. T8 solution heat-treated, cold worked, and artificially aged. (T3+artificial age) T9 solution heat-treated, artificially aged and cold worked. (T6+artificial age) T10 cooled from an elevated temperature shaping process, cold worked, and artificially aged. Usually associated with cast products.(T2+artificial age) The following specific digits have been assigned for stress-relieved tempers of wrought products: T_51 Applies to cold finished rod or bar when stress-relieved by stretching 1 to 3 % permanent set. Stretching is performed after solution heat treatment or after cooling from an elevated temperature shaping process. No straightening takes place after stretching. T_510 Applies to extruded products and to drawn tube when stress-relieved by stretching 1 to 3 % permanent set. Stretching is performed after solution heat treatment or after cooling from an elevated temperature shaping process. No straightening takes place after stretching 1 to 3 % permanent set. T_511 Applies to extruded products and to drawn tube when stress-relieved by stretching 1 to 3 % permanent set. Stretching is performed after solution heat treatment or after cooling from an elevated temperature shaping process. These products may receive minor straightening after stretching to comply with standard tolerances. Subdivisions of "H" Temper-Non-Heat-Treatable Alloys H1 Strain-hardened only. Applies to products which are strain-hardened or cold worked to obtain the desired strength level without supplementary thermal treatments. The number following this designation indicates the degree of strain-hardening. H2 Strain-hardened partially annealed. Applies to products strain-hardened or cold worked more than the desired level by partial annealing. The number following this designation indicates the degree of strain hardening remaining after the partial annealing process. H3 Strain-hardened and stabilized. Applies to products in the magnesium-aluminum class which will age-soften at room temperature after strain-hardening. These products are strain-hardened to the desired amount and then subjected to a low temperature thermal operation which results in a improved ductility. The number following this designation indicates the degree of strain-hardening remaining after the stabilization treatment. The digit following the designation H1, H2 or H3 indicates the degree of strain-hardening  as follows: H1 1/8 hard H2 1/4 hard H3 3/8 hard H4 1/2 hard H5 5/8 hard H6 3/4 hard H7 7/8 hard H8 full hard (approximately 75% reduction after a full anneal). H9 extra hard (limited to certain alloys and/or product forms).