Influence of rotational tool speed on metallurgical characterization of friction stir welded joint of AZ91D and AA2024

Abstract

This study investigated the dissimilar friction stir welding (FSW) of AA2024 and AZ91D and aimed to explore the effect of rotation tool speed (RTS) on welding quality and the formation of intermetallic compounds (IMCs) in the welded region. The optimal welding parameters for achieving a sound weld were determined to be a traverse speed (TS) of 35 mm/min and an RTS of 700 r/min. The presence of two specific intermetallic phases, Al3Mg2 and Al12Mg17, was observed in all joints, with Al12Mg17 showing a tendency to migrate toward the weld surface adjacent to the AZ91D plate, possibly resulting in constitutional liquation during solidification. The results revealed that the morphological characteristics and input heat significantly influenced the formation of IMCs. Moreover, the study highlighted that improper selection of processing parameters, particularly using lower RTS and TS, led to the development of dense layers of IMCs, such as Al12Mg17 and Mg + Al12Mg17, within the stir zone (SZ). Consequently, this led to a decrease in the ultimate tensile strength (UTS) of the FSWed joints. The highest UTS value of 147.26 MPa was achieved with an RTS of 700 r/min and a TS of 35 mm/min, while the lowest UTS value of 113.47 MPa was observed at an RTS of 500 r/min and a TS of 35 mm/min.