Group 7000 (AlZnMg) (Topic: 10008)

The 7000-group contains high strength materials similar to AlCuMg, but with zinc instead of copper as the main alloying element. But copper can also be added, in smaller amounts. Compositions within this system have the highest known strength of all commercial aluminium alloys. The high strength is due to precipitation of MgZn2 particles.

The alloys without copper have a tensile strength somewhat above the strongest of the 6000-alloys. The most widely used alloy contains approximately 4,5% Zn and 1,3% Mg. This alloy has extrudability that is slightly worse than for AW-6082, but the alloy is much less quench sensitive and can be air cooled for much greater wall thicknesses.

The alloys obtain full strength after approximately one month storage at room temperature, which in turn makes the alloy attractive for welding.

The alloys containing copper (AlZnMgCu) attain the highest strength of all aluminium alloys, exceeding normal structural steel. The extrudability is very poor and the alloys are not weldable under normal conditions.

The AlZnMg-alloys are used for structural applications where high mechanical strength is needed and in the automotive industry (e.g. car bumpers). The AlZnMg Cu alloys are used for particularly high stressed components in the aviation- and space industry.