This project aimed at developing an aluminium alloy, primarily for fuselage skin application, that offers a step change in terms of corrosion resistance versus conventional aluminium alloys used for this application.

As the overall purpose of Clean Sky is to offer more eco-friendly solutions, the proposed alloy must also offer properties that allow some weight saving versus the incumbent alloys. This is achieved through mechanical properties, which determine the component thickness, and through density reduction.

The option proposed was to develop an AlMgLi alloy that inherently offers a 10% weight saving by density versus conventional alloys. Further improvements versus the currently flying aircraft can be achieved by design optimization.

Alcan has developed this type of alloy to a Technology Readiness Level 3. Following lab trials, two campaigns at industrial scale were already performed, that demonstrate the capabilities of this alloy type to fulfil the above requirements.

To bring the alloy to TRL6, the proposition was first to roll and heat treat an existing slab to determine the properties according to the precise requirements of the airframers issuing the call. Corrosion tests relevant to the application, with and without protection, fatigue before and after corrosion protection, and large flat panels damage tolerance tests were performed.

A second step consisted of casting, converting and characterising a slightly modified composition, to be determined according to the results obtained in the first step. Minor elements could be tuned in order to obtain the optimum microstructure. In that second step, properties pertaining to the fabrication of components were assessed in addition to the material properties as described above.

Capitalising on Alcan’s experience in airframe technology, the next step was to support the build and testing of a demonstrator.

The project aimed at starting in September 2011. This date had been fixed in agreement with the topic manager due to project planning and casting facility availability (scheduled month n°11).