Abstract
In this research, microstructural events and mechanical behaviors in dissimilar friction stir welding (FSW) of aluminium (Al) alloy AA6082‐AA7075 joints have been evaluated to apply aerospace, defense, and military sectors. FSW parametric effects have a more significant impact on the mechanical performances and microstructure of produced joints. FSW tool rotational speed, welding speed, and tool plunge speed were chosen to make the weld joints. The rotational tool speeds of 1600 rpm and 2300 rpm, welding speeds of 40 mm/min and 60 mm/min, and tool plunge speeds of 20 mm/min and 30 mm/min were set as the upper and lower limits. A constant axial force of 5 kN was maintained throughout the joint fabrication process. A taper pin‐profiled tool was utilized to produce the butt welded joints. Mechanical properties of microhardness, tensile strength, yield strength, elongation, and bending strength of the joints were analyzed. The response of the stir zone microstructure to processing parameters was evaluated using optical microscopy (OM) and fractographic analysis of a tensile specimen shown by scanning electron microscope (SEM). The weld joints produced at 2300 rpm, tool traveling rate of 40 mm/min, and tool plunge speed of 30 mm/min showed the greatest tensile strength of the 191 MPa hardness of 145 Hv at the weld center and also the maximum bending strength of 114.23 N/mm2 was achieved. The lowest bending strength of 25.38 N/mm2 was obtained at 1600 rpm with 60 mm/min due to inappropriate mixing of the base metals and poor joint quality. Furthermore, this study revealed that a higher tool plunge speed facilitates the formation of equiaxed grains in the thermomechanically affected zone (TMAZ) on the advancing side (AS). Additionally, the increment in tool rotational speed significantly improved the tensile strength, weld joint quality, and joint efficiency.
Highlights
Aluminum alloys are lightweight and have more applications in the industrial sector
Appearance of Weld Joints. e schematic top view of the friction stir welding (FSW) samples is shown in Figure 3. e FSW process successfully processed the weld samples using a tool steel M35 grade FSW tool with a tapered pin profile. e physical appearance of the weld joints joined with 1600, 2300 rpm tool rotational speeds and 40, 60 mm/min welding speeds seems good without any defects. e pin plunging speed of 20, 30 mm/min was utilized in this process
It shows the size of the grain particle changing from 6 μm to 12 μm. e frictional heat increased at the weld region due to the increment in the rotational tool speed
Summary
Aluminum alloys are lightweight and have more applications in the industrial sector. By conventional fusion welding techniques, aluminum alloys are tough to weld, and the joint quality is unsuitable due to welding defects like distortion, cracks, and porosity [1]. E FSW tool features like shoulder diameter and taper pin profile are instrumental in producing adequate weld surface quality and better mechanical behaviors of sound weld joints [13]. A large amount of frictional heat is produced in the obtained weld joints based on the FSW process parameters like revolving tool speed (rpm), tool traveling speed (mm/min), pin plunge depth (mm), and axial force (kN) [14]. E effects of the FSW parameters and tool pin profile on the tensile strength, microstructural analysis, hardness, and fatigue behavior of weld joints were experimentally investigated. Many researchers have successfully investigated and reported the microstructural characteristics and mechanical behaviors of dissimilar aluminum alloys processed by FSW. The literature available on the bending characteristics of dissimilar aluminum butt joints between the AA6xxx and AA7xxx series is limited. erefore, this research presents the mechanical properties, microstructural analysis, and bending characteristics of AA6082-AA7075 dissimilar weldments fabricated with various FSW parameters
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