Microstructure evolution of Friction Stir Welded Dissimilar Aerospace Aluminium Alloys

Abstract

Aluminium alloys exhibiting properties such as high strength to weight ratio, high corrosion resistance etc. has made them a choice for many industrial applications. Therefore, joining of aluminium alloys is of utmost importance, especially for the aerospace industry. Friction stir welding (FSW), a clean novel solid-state joining process, is being used to effectively join dissimilar materials for making different parts of space shuttles, aircrafts etc. 2.5 mm thick dissimilar aluminium alloys, AA2219-O and AA7475-T761, were joined using FSW. Evolution of microstructure for the traverse cross section of welded joint was studied. As a result, significant refinement of grains was observed in stir zone along with dissolution and coagulation of strengthening precipitates due to high rise in temperature and severe plastic deformation. Partial recrystallization was observed in TMAZ along with coarsening of grains and strengthening precipitates. In HAZ, coarser grains and strengthening precipitates was observed with no extent of plastic deformation.