ALLOY DESIGNATION SYSTEM

A system of four-digit numerical designations for wrought aluminum and wrought aluminum alloys was adopted by The Aluminum Association in 1954 and became effective on October 1 of that year. The first digit of the designation serves to indicate alloy groups. The last two digits identify the aluminum alloy or indicate the aluminum purity. The second digit indicates modifications of the original alloy or impurity limits.

Aluminum and Aluminum Alloy Groups

A system of four-digit numerical designations is used to identify wrought aluminum and wrought aluminum alloys. The first digit indicates the alloy group as follows:

Aluminum, 99.00 percent minimum and greater .......... 1xxx

Aluminum alloys grouped by major alloying element

Copper ...............................................................   2xxx

Manganese .......................................................    3xxx

Silicon ...............................................................    4xxx

Magnesium .......................................................    5xxx

Magnesium and Silicon ....................................   6xxx

Zinc ...................................................................     7xxx

Other element ...................................................    8xxx

Unused series ..........................................................    9xxx

The last two digits identify the aluminum alloy or indicate the aluminum purity. The second digit indicates modifications of the original alloy or impurity limits.

ALUMINUM — In the 1xxx group for minimum aluminum purities of 99.0 percent and greater, 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 when it is expressed to the nearest 0.01 percent. The second digit in the designation indicates modifications in impurity limits. If the second digit in the designation is zero, it indicates that there is no special control on individual impurities; integers 1 through 9, which are assigned consecutively as needed, indicate special control of one or more individual impurities.

ALUMINUM ALLOYS — In the 2xxx through 8xxx alloy groups the last two of the four digits in the designation have no. special significance but serve only to identify the different aluminum alloys in the group. When new alloys are developed to the point where they become commercially used, these last two digits are assigned consecutively beginning with xx01. The second digit in the alloy designation indicates alloy modifications. If the second digit in the designation is zero, it indicates the original alloy; integers 1 through 9, which are assigned consecutively, indicate alloy modifications.

EXPERIMENTAL ALLOYS— Experimental alloys are also designated in accordance with this system but they are indicated by the prefix X.