Wrought aluminium alloys are identified by a four-digit number registered with the Aluminum Association and widely used in Indian and international standards. The first digit shows the main alloying element:
- 1xxx: 99% or purer aluminium, e.g. 1050, 1100, 1350.
- 2xxx: copper, high strength, e.g. 2014, 2024.
- 3xxx: manganese, e.g. 3003.
- 4xxx: silicon, e.g. 4043 welding wire.
- 5xxx: magnesium, e.g. 5052, 5083.
- 6xxx: magnesium and silicon, e.g. 6063, 6061.
- 7xxx: zinc, e.g. 7075.
- 8xxx: other elements, e.g. 8011 with iron and silicon for foil.
Casting alloys use different systems, such as the three-digit Aluminum Association series (A356, A380), British LM grades and Japanese ADC grades.
Why it matters when buying
- The alloy decides strength, formability, weldability and corrosion behaviour, so always state alloy and temper together.
- 2xxx, 6xxx and 7xxx are heat-treatable; 1xxx, 3xxx and 5xxx gain strength only by cold work.
- Equivalent Indian IS designations exist; ask the supplier to confirm the equivalence on the certificate.
The guide to alloy and temper codes covers this in more depth.