The Aluminium Numbering System

Wrought Aluminium Alloys - The Aluminium Numbering System
Wrought Aluminium Alloys – The Aluminium Numbering System

What is the Aluminium Numbering System?

Aluminium is usually alloyed with several other elements in order to improve various properties such machinability or chemical resistance. As a result, there is a large amount of combinations of various alloying elements that can be combined to achieve the desired properties, this results in a wide variety of aluminium types or grades. To help keep track of all the combinations, an aluminium numbering system is utilised.

The Aluminium Association created the nomenclature and it is the organisation that maintains this designation system that is used internationally. There are many rules for labeling the various types of aluminium alloys. It is important to first know whether the aluminium alloy is wrought or cast. In this article we will focus on wrought aluminium alloys and the numbering system used to identify them.

Wrought Aluminium

Wrought aluminium alloys use a standard 4-digit numbering system. The first digit designates the primary alloying element in the aluminium alloy. An example would be the 1XXX alloy indicating a mostly pure aluminium alloy, whereas a 6XXX alloy would indicate that significant amounts of magnesium (Mg) and silicon (Si) have been added to the aluminium. Below is a useful table detailing the different alloying elements of used in wrought aluminium:

1xxx Pure Aluminium

  • The 1000 series is essentially pure aluminium with a minimum 99% aluminium content by weight. The 1000 series can be work hardened.
2xxx Copper

  • The 2000 series is alloyed with copper and can be precipitation hardened to strengths that are comparable to steel. Formerly referred to as duralumin, these were once the most common aerospace alloys, but due to their susceptibility to stress corrosion cracking, they are increasingly replaced by alloys of the 7000 series in new designs.
3xxx Manganese

  • The 3000 series is alloyed with manganese, and is able to be work hardened.
4xxx Silicon

  • The 4000 series is alloyed with silicon. Some variations of aluminium-silicon alloys intended for casting are also known as silumin, these not included in 4000 series.
5xxx Magnesium

  • The 5000 series is alloyed with magnesium, and offers superb corrosion resistance, making it suitable for marine applications. Additionally, the 5083 alloy has the highest strength of non heat-treated alloys. Most 5000 series alloys include manganese (Mn) as well.
6xxx Magnesium and Silicon

  • The 6000 series is alloyed with magnesium and silicon. Alloys of the series are weldable, easy to machine and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach. The 6061 alloy is one of the most commonly used general-purpose aluminium alloys.
7xxx Zinc

  • The 7000 series is alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminium alloy (ultimate tensile strength up to 700 MPa for the 7068 alloy). Most 7000 series alloys include some magnesium and copper as well.
8xxx Other

  • The 8000 series is alloyed with other elements which are not covered by the above series. Aluminium-lithium alloys are an example of this.

 

The second digit in the above wrought aluminium numbering system would indicate if there has been a special modification to one of the alloying elements. These controls are registered with IADS and require the specific IADS documentation. The last two digits in the above wrought alloy aluminium designation system are used to label and differentiate the specific alloys. These numbers are completely arbitrary except when used in the 1XXX series of aluminium. In the 1XXX series, the last two digits specify the minimum aluminium content between 99% and 100%. As an example, 1050 aluminium would have a minimum pure aluminium content of 99.50%.

Cast aluminium alloys use a similar numbering system except with a decimal point (XXX.X). Similar to wrought aluminium, the first digit in the cast aluminium alloy designation system indicates the major alloying element or elements.

Temper Designations

Temper designations distinguish what processing has been done to the aluminium to increase mechanical properties such as tensile strength and hardness. These designations can follow the digits for both wrought and cast aluminium alloys.

  • F – The “F” designation indicates the alloy is fabricated, and no special processing has been used to increase the alloys mechanical properties.
  • H – The “H” designation indicates the alloy has been strain hardened.
  • O – The “O” designation indicates the alloy is an annealed aluminium alloy.
  • T – The “T” designation indicates that the aluminium alloy has undergone thermal treatment.
  • W – The “W” designation indicates thermal heat treatment has taken place.

Only the 2XXX, 4XXX, 6XXX, and 7XXX series of wrought aluminium alloys are heat treatable. The exception to this is that some of the 4XXX series aluminium alloys are unresponsive to heat treatment.

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Comments (3)

  • jabu skosanaReply

    in numbers or rands how much does aluminium architectural products contribute to the economy of gauteng province+western cape+kzn provinces how big is the aluminium architectural products in these provinces thanx

    30th May 2019 at 10:47 am
    • Shea BethellReply

      Hi Jabu,
      You will need to get the information from GFK or a data statistics company. We dont have the exact statistics you are looking for.
      Best Regards,
      The AT-Group Team.

      3rd Jun 2019 at 10:01 am
  • Leo RobinetteReply

    Wow that was odd. I just wrote an really long comment but after I clicked submit my comment didn’t
    appear. Grrrr… well I’m not writing all that over again. Anyway, just wanted to say fantastic blog!

    26th Nov 2019 at 8:51 am

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