3.6.1 Aircraft alloys

Designers of aircraft require materials that will allow them to produce lightweight, cost-effective structures which are durable and damage tolerant at ambient, sub-zero and occasionally elevated temperatures. As mentioned earlier, strong aluminium alloys date from the accidental discovery of the phenomenon of age-hardening by Alfred Wilm in Berlin in 1906. His work led to the development of the wrought alloy known as Duralumin (Al 3.5Cu 0.5Mg 0.5Mn) which was quickly adopted in Germany for structural sections of Zeppelin airships, and for the Junkers F13 aircraft that first flew in 1919. Since that time, wrought aluminium alloys have been the major materials for aircraft construction which, in turn, has provided much stimulus for alloy development.

Duralumin was the forerunner of a number of 2xxx series alloys including 2014 and 2024 that are still used today. The other major aircraft group of alloys is the 7xxx series. Both classes were considered in Section 3.4 together with the lithium-containing alloys that have been developed as possible substitute lightweight materials.

Materials selection for structural applications in aircraft depends mainly on a daunting variety of performance requirements which are summarised for a typical passenger aircraft in Fig. 3.46. Examples of older and newer alloys that have been used are given below: