Mechanical Behavior and Microstructure of AA6061-T6 Joints Made by Friction Stir Vibration Welding

The friction stir vibration welding (FSVW) method has been proposed as a modified version of the friction stir welding (FSW) method. In the current research, the effect of the FSVW variables on the microstructure and the mechanical properties of the joint made by this welding process was analyzed. In FSVW, the workpiece is vibrated normal to tool traverse direction while FSW is carried out. AA6061-T6 specimens were joined by FSVW as well as FSW, and the obtained joints were compared. The microstructures of the welds were analyzed using metallography techniques. SEM and EBSD were also applied to study the microstructure. The results showed that grain size reduced and hardness increased as the FSVW technique was employed instead of FSW. The results also indicated that the strength and hardness of joints, made by FSVW, increased as vibration frequency increased. It is believed that workpiece vibration, in FSVW, increases the material strain and correspondingly, enhances the dislocation density. More intensified role of dynamic recrystallization in FSVW, compared to FSW, leads to the development of finer grains in the stir zone. It was also concluded that high thermal energy during FSW and FSVW might deteriorate the mechanical properties of the joint and low thermal energy also leads to an unfair joint.