Duralumin Alloys in World War II Heritage Aircraft: Correlations Between Manufacturing Parameters and Alloys’ Properties

Duralumin-type alloys have been employed for structural and non-structural parts of aircraft since the early 1920s up to now. In the European project “PROtection and Conservation of Heritage AirCRAFT” (PROCRAFT), up to 34 aircraft wrecks from World War II from different nations (United States of America, United Kingdom, France, Germany, Italy) were identified. On most of them, the collection of numerous fragments was possible, thus constituting a large sampling group. A metallographic analysis was carried out, and elemental composition, microstructure and hardness were measured. This article focuses firstly on the elemental composition of this group of historical Al alloys. From these data, some fine characteristics specific to the manufacturing countries will be investigated through principal component analysis. Then, on a restricted group constituted of German alloys, we will discuss how some manufacturing parameters, such as micro-alloying and thermo-mechanical treatments, influence the mechanical properties of the assessed aircraft components. Other influencing parameters, linked to the archaeological nature of the parts, are considered and addressed based on a specific study of an alloy collected on a crashed JU88 aircraft originating from the German company Junkers.