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Dr. Dmitri Kopeliovich
Classification of aluminum alloys is established by the International Alloy Designation System (IADS), based on the classification developed by Aluminum Association of the United States.
This classification is accepted by most countries.
Each wrought aluminum alloy is designated by a four digit number.
The first digit indicates the alloy group according to the major alloying element:
1xxx Aluminum 99.0% minimum;
2xxx Copper (1.9%...6.8%);
3xxx Manganese (0.3%...1.5%);
4xxx Silicon (3.6%...13.5%);
5xxx Magnesium (0.5%...5.5%);
6xxx Magnesium and Silicon (Mg 0.4%...1.5%, Si 0.2%...1.7%);
7xxx Zinc (1%...8.2%);
8xxx Others.
The second digit indicates modification of the alloy or impurity limits.
Original (basic) alloy is designated by “0” as the second digit. Numbers 1…9 indicate various alloy modifications with slight differences in the compositions.
In the alloys of the 1xxx series the second digit indicates modifications in impurity limits: 0 means natural impurity limit, 1…9 indicate special control of one or more impurities or alloying element.
The last two digits identify aluminum alloy or indicate the alloy purity.
In the alloys of the 1xxx series the last two digits indicate the level of purity of the alloy:
1070 or 1170 mean minimum 99.70% of aluminum in the alloys, 1050 or 1250 mean 99.50% of aluminum in the alloys, 1100 or 1200 mean minimum 99.00% of aluminum in the alloys.
In all other groups of aluminum alloys (2xxx through 8xxx) the last two digits signify different alloys in the group.
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Each cast aluminum alloy is designated by a four digit number with a decimal point separating the third and the forth digits.
The first digit indicates the alloy group according to the major alloying element:
1xx.x Aluminum 99.0% minimum;
2xx.x Copper (4%...4.6%);
3xx.x Silicon (5%...17%) with added copper and/or magnesium;
4xx.x Silicon (5%...12%);
5xx.x Magnesium (4%...10%);
7xx.x Zinc (6.2%...7.5%);
8xx.x Tin;
9xx.x Others.
The second two digits identify aluminum alloy or indicate the alloy purity.
In the alloys of the 1xx.x series the second two digits indicate the level of purity of the alloy – they are the same as the two digits to the right of the decimal point in the minimum concentration of aluminum (in percents): 150.0 means minimum 99.50% of aluminum in the alloy, 120.1 means minimum 99.20% of aluminum in the alloy.
In all other groups of aluminum alloys (2xx.x through 9xx.x) the second two digits signify different alloys in the group.
The last digit indicates the product form: casting (designated by “0”) or ingot (designated by “1” or “2” depending on chemical composition limits.)
A modification of the original alloy or impurity limits is indicated by a serial letter before the numerical designation. The serial letters are assigned in alphabetical order starting with A but omitting I, O, Q, and X (the letter “X” is reserved for experimental alloys).
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