Weld appearance and microstructural characteristics of friction stir butt barrier welded joints of aluminium alloy to copper

Abstract

Friction stir butt barrier welding, an improved method based on the friction stir butt welding process, in which a barrier was configured on the butt plate, was applied to the Cu–Al combination. The resultant Cu–Al joints presented good appearance when Al was adopted as the barrier. The pin shifting towards the Al side could improve the interior quality of the weld. However, the effect was limited when the pin offset increased to a certain value. As the tool rotation rate increased, the amount and size of the voids decreased first and then increased. There were two types of joint depending on the interfacial morphology: the smooth interface and the chaotic interface. When the pin offset was zero, the interface was occupied by large Cu fragments. As the pin offset increased, the joint interface transited first to the smooth type and then to the chaotic type. As the rotation rate increased, the laminate density around the interface decreased, and the sublayers in the laminates thinned.