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When aluminum that is to be used as an extrusion is combined with a predetermined mixture of one or more elements, it is called an aluminum extrusion alloy. Its end-product performance is determined by both the alloy composition and the method of production. The production method, in turn, strongly influences the final temper of the alloys. Temper is the combination of hardness and strength imparted to a metal by mechanical or thermal treatments. The temper designation is characterized by its metallurgical structures and mechanical properties.

Effects of Alloying Elements
The properties and characteristics of aluminum, such as density, conductivity, corrosion resistance, finish, mechanical properties, and thermal expansion, are modified by the addition of alloying elements. The resulting effect depends upon the principal alloying elements used, as detailed in the table below.

Wrought Alloy Designation

Major Alloying Elements and Typical Alloy Characteristics
1xxx Series Minimum 99% aluminum
High corrosion resistance. Excellent finishability. Easily joined by all methods. Low strength. Poor machinability. Excellent workability. High electrical and thermal 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. Good workability.
4xxx Series Silicon
Not available as extruded products. 
5xxx Series Magnesium
Low to moderate strength. Excellent marine corrosion resistance. Very good weldability. 
6xxx Series Magnesium & Silicon
Most popular extrusion alloy class. Good extrudability. Good strength. Good corrosion resistance. Good machinability. Good weldability. Good formability. Heat treatable. 
7xxx Series Zinc
Very high strength. Good machinability. Heat treatable. 
 

 

Tempers
All aluminum alloys, regardless of product form, are classified as either heat-treatable or nonheat-treatable, depending upon the method used to attain their maximum strength.

  • Nonheat-treatable alloys: 1xxx, 3xxx, and 5xxx series develop strength characteristics through cold work after extruding, if the section shape permits.
  • Heat-treatable alloys: 2xxx, 6xxx, and 7xxx series, which have the highest strength of all aluminum alloys, attain their maximum strength through controlled heat treatment, sometimes at the extrusion press and sometimes in a separate furnace.

The modification methods applied to heat- and nonheat-treatable alloys are listed in the Temper Designation System below.

   F
 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 
H
 Strain-hardened  Cold working used to increase strength and hardness 
T
 Thermally Treated  Thermally treated to produce stable tempers other than F, O, or H 

A complete alloy-temper designation reads like this: 6063-T5. This designation indicates a particular alloy of the 6xxx series (Mg and Si), which is thermally treated by being cooled from an elevated temperature and artificially aged. 

Typical Tempers for Extrusions
O            Fully annealed.
H112      Strain-hardened; used for nonheat-treatable alloys.
T1          Cooled from an elevated temperature and naturally aged.
T4          Solution heat-treated and naturally aged.
T5          Cooled from an elevated temperature and artificially aged.
T6          Solution heat-treated (which may be accomplished for some alloys in-line
              at the extrusion press) and artificially aged.

International Alloy Designations
Follow the link for the Aluminum Association (AA) wrought alloys and the corresponding foreign alloys that are covered by standards used in Austria, Canada, France, Germany, Great Britain, Italy, Spain, Switzerland, and in the Recommendations of the International Organization for Standardization (ISO).  
 
 
 
 
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