Visualization of material flow in 2014 Al alloy friction stir welding process

The material flow in friction stir welding 2014 Al alloy has been investigated using a marker insert technique (MIT). Results show that the material flow is asymmetrical during the friction stir welding process and there are also significant differences in the flow patterns observed on advancing side and retreating side. On advancing side, some material transports forward and some moves backward, but on retreating side, the material only transports backward. At the top surface of the weld, significant material transport occurs due to the action of the rotating tool shoulder. A two-dimension mode was presented, and using this model, the process of material flow can be explained well.