Evaluation of friction-stir welded thick preforms for Aeronautics applications
By Hugo Robe (Institut de Soudure), Amarilys Ben Attar (Institut de Soudure), David Chartier (STELIA Aerospace)

In the aeronautics industry, reduction of the “buy-to-fly” ratio is of great interest especially when using high-performance as well as costly materials. In the large range of aluminium alloys, Al-Li alloys are recent grades which provide an answer to several issues encountered by aircraft manufacturers. However, these materials only have limited use due to their cost. In this work, friction stir welding (FSW) of 2050-T34 aluminium alloys was investigated to manufacture thick preforms for aero-structures. The friction stir welding process enables thick parts to be welded while preserving mechanical properties, developing strategies for weight and raw material savings, reducing chips during machining, and lowering quality issues.

The development of process parameters has been performed and the sensitivity to post-weld heat treatment on the mechanical performance of the structure was evaluated by means of monotonic tensile tests along with fatigue testing. Representative demonstrators (4.5 meters long) have then been successfully manufactured for further testing.

A specific non-destructive testing (NDT) procedure making use of ultrasounds has been developed to inspect the welds and ensure the detectability of potential defects on a lap-joint configuration.
In addition, suggestion of industrial routing including all the manufacturing steps (welding, NDT, machining…) was proposed and discussed in this study. Industrial perspectives will be presented.