F. Eberl, H. Gerard, J. C. Ehrström, Alcan, Voreppe, France; L. Cervi, Alcan CRV, Voreppe, France

Summary:

Welding of aluminum structures is progressing rapidly in the aircraft industry, aiming at manufacturing cost reductions in the order of 20%. After the successful implementation of laser beam welding of fuselage stringers in Airbus A318 and A380, Friction Stir Welding could bring benefit to the fuselage manufacture as a mean to join panels together with less weight and cost penalty compared to riveting. This would reduce also the need for difficult to make very wide sheet.

While ALCAN and others’ studies have demonstrated the improvement to corrosion resistance, and sometimes strength, brought by post-weld aging, the particular application mentioned above would be largely facilitated if friction stir welds could be left in the as-welded temper. Aiming at this objective, a screening study was undertaken, in order to determine the as-welded properties of fuselage sheet with different chemical compositions and initial tempers.

Alloys already on the market (6056, 2024, 2098) and alloys currently under development (2022, 2139, and some 7000 alloys) were friction stir welded. The thickness investigated ranges from 3 to 6 mm. Welding parameters were developed for all alloys. Satisfactory welds are obtained in terms of surface aspect, porosity, cracks and ductility in bending.

Results of microstructure examination, static tensile tests and corrosion tests will be presented. A comparison between the different alloys and tempers available will be made and potential improvement routes will be discussed.