Mechanism of Weld Formation during Friction Stir Welding of Aluminum Alloy

The present work aims at identification of process parameters for sound weld and to understand the mechanism of material matrix movement and weld formation in friction stir welding (FSW) of aluminum alloy. FSW experiments were conducted on 6mm thick AA6061-T6 plates using various rotational and welding speeds. The welded plates were cut along the transverse direction to examine the macro defects. The defect size as a function of welding and rotational speed has been studied, and three parameter zones were identified. They are insufficient material flow zone, defects free zone, and excessive material flow zone. The sound zone is identified in the moderate rotational speed range for each welding velocity that occurs between the insufficient and excessive material flow zone. In the insufficient material flow zone, the defect size is found to be inversely proportional to rotational speed, whereas in the case of excessive material flow zone the defect size is directly proportional to rotational speed. As welding velocity increases, rotational speed is to be increased proportionally to form a sound weld. The relation between weld parameters, temperature, matrix movement, and weld formation has been established.