Aluminum is one of the most common metals on earth. Did you know that it is the 3rd most plentiful element known to man? It is unique in being extremely economical to recycle and there is a healthy secondary metal industry that is working on better techniques to improve the use of these recycled aluminum products.
This article covers the interesting characteristics of different classifications for both wrought aluminum alloys and cast aluminum alloys.
Wrought Aluminum Alloys
By: Timothy Kenney
Wrought aluminum alloys are commonly designated by a four digit number such as 6061, or in the UNS system of identification by the letter A and a five digit number beginning with “9”, such as A96061 for the same alloy. The numbering of alloys is determined by the primary alloying elements that are present as noted below.
|6XXX||6061||Magnesium and Silicon|
*The aluminum content is 99.00% or greater with the last two digits designating the amount in excess of 99%. For example 1060 aluminum contains a minimum of 99.60% aluminum.
Aluminums of 99.00% purity or greater generally have excellent corrosion resistance and high electrical and thermal conductivity. The mechanical properties of this family are low, although they can be increased by cold working.
Typical uses for this alloy are chemical handling equipment and architectural trim. This is because of its superior corrosion resistance, or heat exchangers and electrical conductors because of its good conductivity.
This family of alloys requires a solution heat treatment to achieve optimum mechanical properties. A subsequent precipitation treatment is also commonly performed. The corrosion resistance of alloys in this family is generally poorer than other aluminum alloys but their strength can exceed that of low carbon steel.
Typical applications for this alloy are structural, where a good strength to weight ratio is required. Wheels and truck suspensions are also common applications.
This family of alloys is not heat treatable, but may be hardened by cold working. These alloys have good formability and weldability with moderate strength. The 3000 series aluminums are used in highway signs, cooking ware, eating utensils and siding.
The high solubility of silicon (up to 12%) results in a significant lowering of the melting point without subsequent brittleness. Accordingly, this family is commonly used as a brazing alloy. This family of alloys is not generally heat treatable and the high wear resistance of high silicon alloys is sometimes used.
Like the 3000 series aluminum alloys, this group is not heat treatable, but has a moderate to high strength and responds to cold working. This family is readily weldable, and its good corrosion resistance makes it common in marine applications.
This is the most familiar family of the alloys. This family is heat treatable and has moderate strength, formability, weldability and corrosion resistance. Structural applications are the most common use for this alloy family.
The alloys in this family are heat treatable to relatively high strengths. The corrosion resistance of the family is good to poor and particularly is susceptible to stress corrosion cracking. Weldability is faire to poor. Common applications for this alloy family includes transportation equipment and airframes.
Cast Aluminum Alloys
Cast aluminum alloys follow a similar pattern with a three digit designation followed by a decimal digit such as 356.0. In the UNS system of identification, by the letter A and a five digit number beginning with “0” such as A03560 for the same alloy. The first digit in the numbering of alloys is determined by the primary alloying elements that are present as noted below. The second and third digits alloying elements that are present as noted below. The second and third digits have no significance except for identifying various alloys within the group. The digit to the right of the decimal indicates the product form (0 for castings, 1 for ingot, and 2 for a narrower composition).
|Numerical Designation||Example||Alloying Element(s)|
|3xx.x||355.0||Silicon, w/Cu and/or Mg|
*Aluminum content at least 99.00%.
If you would like a pdf version of this article please click the following link Wrought Aluminum Alloys (June 2015).