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.