Control of abnormal grain growth in friction stir welded aluminium by zirconium additionsWednesday (06.11.2019) 17:00 - 17:20 Part of:
Friction Stir Welding (FSW) is a well-established solid-state joining process for materials such as aluminium. The compositional modification of an alloy is an additional feature of this technique, then called Friction Stir Processing (FSP). In Al-Li-Cu alloys, such as AA2195 aluminium, abnormal grain growth (AGG) can be a crucial issue during post-processing of the produced welds, whilst the alloy contains zirconium for grain boundary stabilisation. Both, the microstructural stability during subsequent heat treatment as well as the mechanical properties in general can be optimized by intermixing specific micrometer-sized metal powders as well as metal foils. By dispersing additional zirconium powder inside a matrix of AA2195 aluminium during FSW, the formation of abnormal grains can be reduced, if suitable processing parameters are used. Using optical microscopy, the reduction of the secondary recrystallized area can be revealed. In addition, the formation of intermetallic phases, acting as pinning particles to hinder AGG, can be evaluated using transmission electron microscopy (TEM). Furthermore, electron backscatter diffraction (EBSD) provides insights on the changes of the crystallographic texture of the welding regions both post-weld and after subsequent heat treatment. The outcomes can be utilized in future research to understand recrystallisation phenomena in fine-grained aluminium after plastic deformation.