The Effect of Tool Rotation Speed on the Formation of Eutectic Structure during Friction Stir Welding of Aluminum to Magnesium

Abstract

Friction stir welding (FSW) is a solid-state welding process capable of joining a wide range of light metals. However, liquation and solidification may occur during joining of dissimilar metals which leads to eutectic formation. This article aims to discover the influence of tool rotation speed on the formation of eutectic structure during friction stir welding of aluminum to magnesium. To do so, friction stir welding was performed at 600 and 950 rpm to join pure aluminum and ECO-AZ91 magnesium alloy in a lap configuration. In order to investigate the influence of the welding speed, the welding speeds of 23.5 and 37.5 mm/min were also chosen. Scanning electron microscopy (SEM) was used to study the microstructure of the joints. A shear-tensile test was used to evaluate the joints’ strengths. The fracture surfaces were also studied by SEM. The results revealed that changing the rotation speed directly affects the eutectic formation, whereas the welding speed had no influence. A lower rotation speed resulted in a thin, continuous intermetallic layer, whereas a higher speed led to the formation of a massive Mg-Al12Mg17 eutectic microstructure. The formation of eutectic, as an indicative of liquation, may affect the material flow during the process due to decreasing the friction coefficient between the tool and material. The macrostructure analyses showed that the phase evolution as well as the mechanism of material flow are highly affected by liquation.

Comprehensive Study on the Properties of AZ91/x-Si3N4 Composites for Their Prospective Application

“…Guan et al [22] reported, in their review, 72-84 and 44-65 hardness (HV) for AZ91/CNT and SiC/Mg composites, respectively. Further, Dudek et al [34] found the hardness result to be 80 HBN for Mg recycled waste composites, and similar results have been reported by other researchers [35][36][37][38]. It is evident that the hardness results in the present study reflect the previously reported results.…”

A Review of Optimization and Measurement Techniques of the Friction Stir Welding (FSW) Process

“…Cylindrical threaded Medium-carbon steel [97] AA6061-T6 and Ti6Al4V Cylindrical and tapered WC with 10% Co [98] Pure titanium (CP-Ti) and Ti6Al4V sheets Truncated conical [47] Al 6061-T6 to AISi 316 stainless steel Cylindrical WC-Co [99] AA1050 and AZ91 Cylindrical H13 steel [100] AA6061-T6 and pure Cu Cylindrical --- [101] Pure Al-pure Cu Cylindrical, tapered, straight triangle, and straight square W302 steel [102] Galvanized steel (GS) and mild steel Q235 Conical tapered WC [103] AZ31-AM60 --Tool steel [104] Table 3. FSW machines and characteristics [105].…”