Friction stir welding of precipitation strengthened aluminium alloys: scope and challenges

High strength aluminium alloys are very attractive for high structural efficiency in aerospace structures. However, the full potential of these alloys is not realised because of lower joint efficiencies. Most of the high strength aluminium alloys use precipitation strengthening as the primary strengthening mechanism. Heat flux during friction stir welding of precipitation strengthened aluminium alloys correlates with the joint efficiency. The best joint efficiency results are observed in a narrow intermediate heat flux region. The origin of this is discussed in terms of precipitate dissolution, reprecipitation and coarsening. Low intensity post-weld plastic deformation and design of dispersion containing aluminium alloys are suggested as approaches to enhance joint efficiency in friction stir welded structures.