Study of desirable precipitate-strengthening effects on friction-stir welded joints of third-generation Al–Cu–Li alloys

A friction-stir welded Al–Cu–Li alloy plate with desirable mechanical performance has been obtained using specific parameters. The microstructures of the nugget zone were systematically characterised and nano-sized phases, including δ′, θ′ and T1 were found in its matrix. These phases enhance the strength of the joint to a level comparable with the base metal. The results provide the means of obtaining a reliable and low-cost friction-stir weld (FSW) joint for T3-tempered Al–Cu–Li alloy plates without any post-welding heat treatments. This study shows that, by using appropriate parameters of FSW, the microstructures and mechanical precipitates of the nugget zone can be controlled to enhance the weld quality.