Friction stir overlap welding of 2124 Aluminium plate

Abstract

In this ongoing investigation, experimental results of friction stir welding (FSW) applied to highthickness 2124 aerospace aluminium alloy are discussed. Flanges of 30 mm high are produced onto a44 mm thick plate by two consecutive overlap welds in this non-fusion weldable material, followed by a finalmilling step. This approach results in significant material savings compared to the conventional productionroute, which consists of milling out the entire part starting from a high-thickness plate. Furthermore, theflanges built up by FSW consist fully of fine-grained material. Due to the nature of the processing route, thenugget zone of the first weld pass is partially reheated by the second weld pass. The influence of parentmaterial temper (i.e., T851 or T4) on friction stir welding characteristics is studied; it is noted that in T4temper, a significant increase in welding speed can be obtained compared to T851. The softer T4 temperalso causes less danger of tool fracture, which allows incorporating more features to the pin and shoulderof the tool. During this investigation, the emphasis is put on microstructural characterisation andmicrohardness testing of various zones in the weld.