Aluminium alloys

Aluminium alloys (or aluminum alloys; see spelling differences) are alloys in which
aluminium (Al) is the predominant metal. The typical alloying elements are copper,
magnesium, manganese, silicon, tin and zinc. There are two principal classifications,
namely casting alloys and wrought alloys, both of which are further subdivided into the
categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for
wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys
yield cost-effective products due to the low melting point, although they generally have
lower tensile strengths than wrought alloys. The most important cast aluminium alloy
system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good
casting characteristics. Aluminium alloys are widely used in engineering structures and
components where light weight or corrosion resistance is required.

Alloys composed mostly of aluminium have been very important in aerospace manufacturing
since the introduction of metal skinned aircraft. Aluminium-magnesium alloys are both
lighter than other aluminium alloys and much less flammable than alloys that contain a
very high percentage of magnesium.