Effect of Tool Pin Profile on Mechanical and Wear Properties of Friction Stir Welding of Dissimilar AA6061 and AA5052 Aluminum Alloys

Abstract

The main objective for the existing research needs to identify the appropriate friction stir weld tool pin profile for welding distinct aluminum alloys AA6061 and AA5052. To investigate their effect on tensile strength, micro-hardness and wear characteristics of dissimilar joints, four separate tool pin forms were utilized: straight cylindrical (SC), straight threaded cylindrical (STC), tapered cylindrical (TC), and straight square (SS). Joints were produced with different tool pin profiles even at a constant rotational speed of 1000 rpm and two different table traverse speed of 60 and 80 mm/min. A SC tool pin design has been found to generate surface galling defects, while a TC tool pin profile generates inadequate heat diffusion as well as defective morphology of the surface. The results showed that tool pin profiles had an important influence on the mechanical characteristics of dissimilar joints. Threaded cylindrical tool pin profile yielded a higher tensile strength of 231 MPa besides a joint efficiency around 74.5 %, while the square tool pin profile obtained a maximum microhardness of 94 HV in the stir region. Grain size in the stir zone was enhanced through adjustments in the design of the tool pin profile and the average grain size for the square and threaded cylindrical tool pin profile was 35 and 39 µm. The highest hardness value was observed in the weld NZ near to advancing side of AA6061, and the minimum hardness value was observed throughout the HAZ near retreating side of AA5052 Al Alloys. Among all pin profiles, STC and SS pin profiles had been identified to be appropriate tool pin profiles of friction stir welding of AA6061–AA5052 Al alloy.