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Audrey COCHARD phD defense

PhD thesis entitled : Microstructures and mechanical properties of Duralumin alloys from the Breguet 765 n°504 64-PH.
Historical and material sciences approach.

The thesis will be held Tuesday, November 8th 2:00 p.m. in CEMES conference room.


Jury members

  • M. Loïc Bertrand, Directeur de l’unité IPANEMA, synchrotron Soleil, Saclay (rapporteur)
  • Mme Patricia Donnadieu, DR, SIMaP, Grenoble (rapporteur)
  • M. Philippe Goudeau, DR, Pprime, Poitiers (examinateur)
  • M. Med Kechidi, Prof., LEREPS, université Toulouse I - Capitole (examinateur)
  • M. Philippe Sciau, DR, CEMES (Directeur de thèse)
  • M. Jean-Marc Olivier, Prof., FRAMESPA, université Toulouse II - Jean Jaurès (co-directeur de thèse)
  • Mme Solenn Reguer, Scientifique de ligne DIFFABS, synchrotron Soleil, Saclay (co-encadrante de thèse, invitée)



Industrially produced since 1910 and used for the construction of Breguet XIV in 1916, the duralumins (Al-Cu-Mg alloys) are the first age-hardening aluminum alloys that were at the origin of the aeronautics development. Easier to work and representing a guarantee of security, they quickly supplanted wood and hessian originally used. Although Al-Zn-Cu alloys of the 7xxx family and composite materials are more widely used today, these Al-Cu-Mg alloys of the 2xxx family remain the reference material for aircraft structures. However, although it is an industrial material, with a large production of written documents, the archiving policy applied by manufacturers causes a loss of information. The management of documents is indeed difficult and expensive. Companies throw files away when the data are considered as out of date. There is thus a difficulty to retrieve pertinent chemical and physical data of material used in aircraft construction, but also to understand the choices made about the material and process used by the manufacturers.

The renovation of the Breguet 765 Sahara n°504 64-PH is an opportunity to study aeronautical duralumins of the late 1950s. This aircraft is interesting for two reasons. On the one hand, it is being renovated by the association Ailes Anciennes Toulouse. Due to corrosion, a lot of elements need to be replaced. It is then possible to recover these elements before they are permanently lost, with the information contained therein. Moreover, this aircraft was built in the post-war period. In addition to interest of the French state for aeronautics as recovery symbol, these alloys are well exploited due to the large production of military aircraft during the Second World War.

By comparing laboratory analysis with archival and current literature, it is possible to give a feedback on these ancient materials. We can compare what was done with what was originally planned in the design of the aircraft and complete the known data of these materials with current metallurgical technical analysis. These studies include an analysis of the nature and microstructure of the alloys from the microscopic scale (optical microscopy, scanning electron microscopy, X-ray diffraction) at the nanoscale (transmission electron microscopy, atom probe tomography), but also the mechanical properties (hardness and tensile testing). As analysis reports which can inform us about the initial state of the materials used do no longer exist, archival documents used for reference come from various sources : scientific and technical journals which inform us about the metallurgical and aeronautical context of the era, some Breguet standards which also provide information about the type of materials used by the manufacturers and Breguet 765 specific documents on materials intended for this aircraft. The approach coupling materials analysis and archives documents allows the understanding of these alloys evolution (nature and fabrication) in a a specific context (political and industrial). These alloys can also be a first reference for aeronautical duralumins of the 1950s and contribute to the study of the long-term evolution of mechanical properties compared to minimum values required by the manufacturer.