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.