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How are wrought aluminum alloys identified by their four-digit numbers?
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aluminum processing
Rolls of processed aluminum.
Wrought aluminum alloys are identified using a four-digit numerical system established by the Aluminum Association of the United States. In this system, the first digit indicates the major alloying element or group of elements present in the alloy.1
The classification for the first digit is as follows:
- 1XXX: Aluminum (at least 99 percent pure)
- 2XXX: Copper
- 3XXX: Manganese
- 4XXX: Silicon
- 5XXX: Magnesium
- 6XXX: Magnesium-Silicon
- 7XXX: Zinc
- 8XXX: Other elements1
While the first digit identifies the primary alloying constituent, the subsequent digits provide further specification for the specific alloy composition.1