Wrought Aluminum Alloy Designation System

The Aluminum Association Wrought Alloy Designation System consists of four numerical digits, sometimes with alphabetic prefixes or suffices, but normally just the four numbers:

• The first digit defines the major alloying class of the series starting with that number.

• The second defines variations in the original basic alloy; that digit is always a 0 for the original composition, a 1 for the first variation, a 2 for the second variation, and so forth; variations are typically defined by differences in one or more alloying elements of 0.15–0.50% or more, depending upon the level of the added element.

• The third and fourth digits designate the specific alloy within the series; there is no special significance to the values of those digits, and they are not necessarily used in sequence. Table 1 shows the meaning of the first of the four digits in the wrought alloy designation system. The alloy family is identified by that number and the associated main alloying ingredient(s), with three exceptions:

• Members of the 1000 series family are commercially pure aluminum or special-purity versions and as such do not typically have any alloying elements intentionally added; however they do contain minor impurities that are not removed unless the intended application requires it.

3 Designation Systems 65

• The 8000 series family is an ‘‘other elements’’ series, comprised of alloys with rather unusual major alloying elements such as iron and nickel.

• The 9000 series is unassigned.

The major benefit of understanding this designation system is that one can tell a great deal about the alloy just from knowledge of which it is a member. For example:

• As indicated earlier, the 1xxx series are pure aluminum and its variations; compositions of 99.0% or more aluminum are by definition in this series. Within the 1xxx series, the last two of the four digits in the designation indicate the minimum aluminum percentage. These digits are the same as the two digits to the right of the decimal point in the minimum aluminum percentage specified for the designation when expressed to the nearest 0.01%. As with the rest of the alloy series, the second digit indicates modifications in impurity limits or intentionally added elements. Compositions of the 1xxx series do not respond to any solution heat treatment but may be strengthened modestly by strain hardening.
• The 2xxx series alloys have copper as their main alloying element and, because it will go in significant amounts into solid solution in aluminum, they will respond to solution heat treatment; they are referred to as heat treatable.
• The 3xxx series alloys are based on manganese and are strain hardenable; they do not respond to solution heat treatment.
• The 4xxx series alloys are based on silicon; some alloys are heat treatable, others are not, depending upon the amount of silicon and the other alloying constituents.
• The 5xxx series alloys are based on magnesium and are strain hardenable, not heat treatable.
• The 6xxx series alloys have both magnesium and silicon as their main alloying elements; these combine as magnesium silicide (Mg2Si) following solid solution, and so the alloys are heat treatable. • The 7xxx series alloys have zinc as their main alloying element, often with significant amounts of copper and magnesium, and they are heat treatable.
• The 8xxx series contain one or more of several less frequently used major alloying  elements like iron or tin; their characteristics depend on the major alloying element(s).
The compositions of a representative group of widely used commercial wrought aluminum alloys are given in Table 2, from Aluminum Standards and Data2 and other Aluminum Association publications.

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J. G. Kaufman
Kaufman Associates
Columbus, Ohio

Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright  2006 by John Wiley & Sons, Inc.

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