Aluminium–copper alloys

Aluminium–copper alloys (AlCu) are aluminium alloys that consist largely of aluminium (Al) and traces of copper (Cu) as the main alloying elements. Important grades also contain additives of magnesium and silicon (AlCu(Mg,Si)), often manganese is also included to increase strength (see aluminium-manganese alloys). The main area of application is aircraft construction. The alloys have medium to high strength and can be age-hardened. They are both wrought alloy. Also available as cast alloy. Their susceptibility to corrosion and their poor weldability are disadvantageous.

Duralumin is the oldest variety in this group and goes back to Alfred Wilm, who discovered it in 1903. Aluminium could only be used as a widespread construction material thanks to the aluminium-copper alloys, as pure aluminium is much too soft for this and other hardenable alloys such as aluminium-magnesium-silicon alloys (AlMgSi) or the naturally hard (non-hardenable) alloys.

Aluminium–copper alloys were standardised in the 2000 series by the international alloy designation system (IADS) which was originally created in 1970 by the Aluminum Association. 2000s series includes 2014 and 2024 alloys used in airframe fabrication.