Friction stir overlap welding of 2124 Aluminium plate

In this ongoing investigation, experimental results of friction stir welding (FSW) applied to high- thickness 2124 aerospace aluminium alloy are discussed. Flanges of 30 mm high are produced onto a 44 mm thick plate by two consecutive overlap welds in this non-fusion weldable material, followed by a final milling step. This approach results in significant material savings compared to the conventional production route, which consists of milling out the entire part starting from a high-thickness plate. Furthermore, the flanges built up by FSW consist fully of fine-grained material. Due to the nature of the processing route, the nugget zone of the first weld pass is partially reheated by the second weld pass. The influence of parent material temper (i.e., T851 or T4) on friction stir welding characteristics is studied; it is noted that in T4 temper, a significant increase in welding speed can be obtained compared to T851. The softer T4 temper also causes less danger of tool fracture, which allows incorporating more features to the pin and shoulder of the tool. During this investigation, the emphasis is put on microstructural characterisation and microhardness testing of various zones in the weld.