Flow analysis of materials in friction stir welding

Abstract

The aim of this study was to analyze the flow behavior of materials in friction stir welding (FSW) of magnesium (Mg) alloy to aluminum (Al) alloy materials at a low rotational speed of 300 rpm and at a low welding speed of 50 mm/min. It was observed that during the dissimilar welding at 300 rpm, some of the material of the advancing side (AS) rotated almost 360° and transferred to the position just behind the previous position, i.e. initial AS position and some of the material of leading edge region transferred to the trailing edge region and such a change continued. Material transfer takes place layer by layer from front to back portions of the FSW tool; a thin layer of material adhered to the tool in the front portion for every half rotation and transferred to the back portion of the tool and this repeated in subsequent rotations. Wrinkle formation began at the front side of the forward moving tool and as the material transferred to backside they became an onion ring pattern, and this was inevitable because the formation of onion rings instantly in the backside region of the tool was clearly impossible.