Although the properties and characteristics of wrought aluminium alloy products are significantly influenced by their complete thermal history, including the heating associated with hot working, the most important effects are those established by the final heat treating operations...
Heat treating, defined broadly, includes all of the controlled heating and cooling operations performed on a metal or alloy in the solid state for the purpose of altering its structure or properties. The thermal processes applied to ingots prior to working and during the intermediate stages of fabrication, as well as those employed after the final working operation, come under this broad definition.
Although the properties and characteristics of wrought aluminium alloy products are significantly influenced by their complete thermal history, including the heating associated with hot working, the most important effects are those established by the final heat treating operations.
The temper designation system, according to ANSI H35.1(M), is used for all forms of wrought and cast aluminium and aluminium alloy, except ingot. It is based on the sequences of basic treatments used to produce the various tempers. The temper designation follows the alloy designation, the two being separated by a hyphen.
Basic temper designations consist of letters. Subdivisions of the basic tempers, where required, are indicated by one or more digits following the letter. These designate specific sequences of basic treatments, but only operations recognized as significantly influencing the characteristics of the product are indicated. If some other variation of the same sequence of basic operations is applied to the same alloy, resulting in different characteristics, additional digits are added to the designation.
The basic temper designations are as follows:
| F | As fabricated. Applies to wrought products that acquire some temper from shaping processes in which no special control is exercised over the amount of strain hardening or thermal treatment. For wrought products in this temper, there are no mechanical-property limits. Applies to castings in the as-cast condition if the alloy is also regularly produced in heat-treated tempers. | | O | Annealed (wrought products only). Applies to the softest temper of wrought products. | | W | Solution heat treated. An unstable temper applicable only to alloys that age at room temperature after solution heat treatment. This designation is specified only when the period of natural aging is indicated; for example: W (0.5 hr). | | T | Heat treated to produce stable tempers other than F or O. Applies to wrought and cast products that are heat treated, with or without supplementary cold working to produce stable tempers. | |
The T is always followed by one or more digits. Numerals 1 through 10 indicate specific sequences of treatments:
| T1 | Naturally aged to a substantially stable condition. Applies to products in which partial solution of the alloying elements is provided by elevated-temperature, rapid-cool fabrication. | | T2 | Annealed (cast products only). Designates a temper produced by a type of annealing treatment used to improve ductility and increase dimensional stability of castings. | | T3 | Solution heat treated, cold worked, and naturally aged to a substantially stable condition. Applies to products that are cold worked to improve strength, or in which the effect of cold work associated with flattening or straightening is recognized in applicable specifications. Different amounts of cold work are denoted by a second digit. | | T4 | Solution heat treated and naturally aged to a substantially stable condition. Applies to products that are not cold worked after solution heat treatment, or in which the effect of cold work associated with flattening or straightening may not be recognized in applicable specifications. | | T5 | Artificially aged only. Applies to products that are artificially aged after an elevated-temperature, rapid-cool fabrication process, such as casting or extrusion, to improve strength and/or dimensional stability. | | T6 | Solution heat treated and artificially aged. Applies to products not cold worked after solution heat treatment, or in which the effect of cold work associated with flattening or straightening may not be recognized in applicable specifications. | | T7 | Solution heat treated and averaged. Applies to products that are solution heat treated and artificially aged beyond the condition of maximum strength, to provide controlled special characteristics, such as dimensional stability, lower residual stresses, or improved resistance to corrosion. | | T8 | Solution heat treated, cold worked, and artificially aged. Applies to products that are cold worked to improve strength, or in which the effect of cold work associated with flattening or straightening is recognized in applicable specifications. Different amounts of cold work are denoted by a second digit. | | T9 | Solution heat treated, artificially aged, and cold worked. Applies to products that are cold worked as a final operation, to improve strength. | | T10 | Artificially aged and cold worked. Applies to products that are artificially aged after an elevated-temperature, rapid-cool fabrication process, such as casting or extrusion, and then cold worked to improve strength. | |
A period of natural aging may occur between the operations listed for tempers T3 through T10. Control of this period may be necessary to achieve the desired characteristics.
The following designations involving additional digits are assigned to stress-relieved tempers of wrought products:
| Tx51 | Stress relieved by stretching (a). Applies to products that are stress relieved by stretching the following amounts after solution heat treatment: plate - 0.5 to 3% permanent set; rod, bar and shapes -1 to 3% permanent set. This designation applies directly to plate and rolled or cold finished rod and bar. These products receive no further straightening after stretching. Additional digits are used in the designations for extruded rod, bar, shapes and tube as follows: Tx510 applies to products that receive no further straightening after stretching; Tx511 applies to products that receive minor straightening after stretching to comply with standard straightness tolerances. | | Tx52 | Stress relieved by compressing (a). Applies to products that are stress relieved by compressing after solution heat treatment, to produce a nominal permanent set of 2.5%. | | Tx53 | Stress relieved by thermal treatment (a). | |
(a) The letter x represents digits 3, 4, 6, or 8, whichever is applicable.
The following temper designations are assigned to some wrought products that are heat treated by the user:
| T42 | Solution heat treated (b). | | T62 | Solution heat treated and artificially aged (b). | |
(b) Exceptions not conforming to these definitions are 4032-T62 and 6101-T62.