P. Lequeu, Alcan Pechiney Rhenalu, Issoire, France; F. Eberl, Alcan Rhenalu, Issoire Cedex, France; S. Jambu, PECHINEY Aviatube, Montreuil-Juigné, France; T. Warner, A. Danielou, Alcan, Voreppe, France; B. Bes, Alcan CRV, Voreppe, Cedex, France
Aluminium-lithium alloys of the so-called third generation were introduced mostly as plates in the early 1990’s. The drawbacks of the previous Al-Li alloy generation, like low ST properties and poor thermal stability, were eliminated thanks to the adoption of lower Li contents. Alloys such as 2195 or 2297 found their first industrial application in space and fighter aircraft application.
Recently, increases in fuel price and the subsequent need to reduce aircraft weight have led the commercial airframe manufacturers consider anew the use of such low density alloys in various structural parts currently produced in standard 2xxx and 7xxx qualities. Since 3rd generation Al-Li alloys were driven by military and space applications, they often exhibit damage tolerance properties which are not fully compatible with their use on commercial aircraft. This is the reason why Alcan Aerospace has worked over the last few years to develop appropriate Al-Li chemistries and their associated thermo-mechanical processing, based on commercial aircraft typical requirements.
The paper will illustrate some of the fundamentals behind the choice of chemistries, as well as the property balance generated at an industrial scale on a selection of those alloys. It will be shown that Al-Li properties can match and often exceed those of the corresponding baseline alloys, with the additional benefits of lower density, higher modulus and better corrosion resistance.
Examples will include alloys like 2050 for medium to thick plates, 2196 for heavy & small gauge extruded sections, as well as 2198 for sheet. Data on new high strength and / or high damage tolerance Al-Li alloys will also be shown for the full range of typical wing and fuselage applications.
Summary: Presentation is highlighting status of aluminium lithium development activities at Alcan, in the form of plates, sheets and extruded sections for typical wing and fuselage applications. Rationale behind the choice of chemistries and thermo-mechanical processing will also be explained.
