Aluminum Extrusion Alloys & Tempers
What is an extrusion alloy? Simply put, an aluminum extrusion alloy is a predetermined mixture of one or more elements together with aluminum to be heated and hydraulically pressed through an extrusion die.
Pure aluminum has minimal commercial use and is typically alloyed with other elements to gain strength or other desired physical attributes. The major alloy designations, compositions, and characteristics are as follows:
| Alloy Designation | Major Alloying Elements & Alloy Characteristics |
|---|---|
| 1xxx Series | Minimum 99% Aluminum: High corrosion resistance. Excellent finishability. Easily joined by all methods. Non-heat-treatable. Low strength, poor machinability. Excellent workability. High electrical conductivity. |
| 2xxx Series | Copper: High strength. Relatively low corrosion resistance. Excellent machinability. Heat treatable. |
| 3xxx Series | Manganese: Low to medium strength. Good corrosion resistance. Poor machinability. Non-heat-treatable. Good workability. |
| 4xxx Series | Silicon: Not available as extruded products |
| 5xxx Series | Magnesium: Low to moderate strength. Excellent marine corrosion resistance. Very good weldability. Non-heat-treatable |
| 6xxx Series | Magnesium & Silicon: Most popular extrusion alloy class. Good strength. Good corrosion resistance. Good machinability. Good weldability. Good formabiity. Heat treatable. |
| 7xxx Series | Zinc: Very high strength. Poor corrosion resistance. Good machinability. Heat treatable. |
Tempers
Beyond alloy selection, temper, which is the hardness and strength imparted to the metal by mechanical or thermal treatment, determines the ultimate physical performance of an aluminum extrusion.
Non-heat-treatable alloys, including1xxx, 3xxx, and 5xxx series, develop strength via cold work after extruding, if the section shape permits.
Heat-treatable alloys, including 2xxx,6xxx, and 7xxx series, have the highest strength of all aluminum alloys and attain their maximum strength through controlled heat treatment, often in a special furnace. Temper designations are as follows:
| Typical Extrusion Tempers | Description | Details |
|---|---|---|
| r | As Extruded | No special control over thermal conditions or strain-hardening; no mechanical property limits |
| O | Annealed | Thermally treated to obtain the lowest strength temper |
| H112 | Strain-hardened | Strain-hardened; used for nonheat-treatable alloys. |
| T1 | Thermally Treated | Cooled from an elevated temperature and naturally aged. |
| T4 | Thermally Treated | Solution heat-treated and naturally aged. |
| T5 | Thermally Treated | Cooled from an elevated temperature and artificially aged. |
| T6 | Thermally Treated | Solution heat-treated and artificially aged |
A complete alloy-temper designation reads like this: 6063-T5. This indicates a particular 6xxx series (Mg, Si) alloy which is thermally treated by cooling from an elevated temperature and artificially aged.
For additional information, including performance parameters, on commonly used aluminum extrusion alloys, click here.
Note: International alloy designations vary from those used in the US. Click here for a table of those foreign alloys that are essentially equivalent in composition to those commonly used in the US.
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