Abstract
The current work presents a detailed investigation for the effect of a wide range friction stir welding (FSW) parameters on the dissimilar joints’ quality of aluminum alloys. Two groups of dissimilar weldments have been produced between AA5083/AA5754 and A5083/AA7020 using tool rotational rates range from 300 to 600 rpm, and tool traverse speeds range from 20 to 80 mm/min. In addition, the effect of reversing the position of the high strength alloy at the advancing side and at retreating side has been investigated. The produced joints have been investigated using macro examination, hardness testing and tensile testing. The results showed that sound joints are obtained at the low heat input FSW parameters investigated while increasing the heat input results in tunnel defects. The hardness profile obtained in the dissimilar AA5083/AA5754 joints is the typical FSW hardness profile of these alloys in which the hardness reduced in the nugget zone due to the loss of the cold deformation strengthening. However, the profile of the dissimilar AA5083/AA7020 showed increase in the hardness in the nugget due to the intimate mixing the high strength alloy with the low strength alloy. The sound joints in both groups of the dissimilar joints showed very high joint strength with efficiency up to 97 and 98%. Having the high strength alloy at the advancing side gives high joint strength and efficiency. Furthermore, the sound joints showed ductile fracture mechanism with clear dimple features mainly and significant plastic deformation occurred before fracture. Moreover, the fracture in these joints occurred in the base materials. On the other, the joints with tunnel defect showed some features of brittle fracture due to the acceleration of the existing crack propagation upon tensile loading.
Highlights
AA5754 and AA5083 are aluminum magnesium alloys, and their most prominent features are the high corrosion resistance and good formability
The friction stir welding (FSW) of dissimilar aluminum alloys combinations has been studied extensively, which proved the potential of the process to join these alloy combinations [4,5,6]
Three commercial aluminum alloys AA5083-O, AA5754-H14 and AA7020-T6 were chosen for producing dissimilar friction stir butt welds
Summary
AA5754 and AA5083 are aluminum magnesium alloys, and their most prominent features are the high corrosion resistance and good formability. The placement of the higher strength aluminum alloys at the advancing side (AS) or at the retreating side (RS) affects material flow as it strongly influences material the stirring and flow behavior [10,11]. This can be a crucial parameter affecting the final joint microstructure, when the selected combinations of base material (BM) have significant differences in their mechanical properties, microstructure and texture [4,12,13,14,15,16]
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