OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 5 No. 4 2023 Ta b l e 5 Tensile test results of joints fabricated with cylindrical threaded pin profile tool Properties 320 rpm, 40 mm/min 400 rpm, 45 mm/min 575 rpm, 60 mm/min Tensile strength (MPa) 138 130 142 Joint Efficiency (%) 82.6 77.8 85 Ta b l e 6 Tensile test result of joints fabricated with cylindrical taper pin profile tool Properties 320 rpm, 40 mm/min 400 rpm, 45 mm/min 575 rpm, 60 mm/min Tensile strength (MPa) 119 115 123 Joint Efficiency (%) 71.2 68.8 73.6 For the taper cylindrical pin profile, the joint efficiency and the tensile strength are highest at 575 rpm and 60 mm/min i.e. 73.6 % & 123 MPa (table 6). Lower values of rotation speed (320 rpm and 45 mm/min) result in lower joint efficiency and tensile strength i.e. 71.25 % & 119 MPa. Intermediate values of rotation speed (400 rpm and 50 mm/min) also give slightly lower values of the joint efficiency and the tensile strength i.e. 68.86 % and 115 MPa. Overall, it appears that 575 rpm and 60 mm/min are the optimal operating conditions for achieving maximum joint efficiency and tensile strength, regardless of whether a taper cylindrical pin profile or a threaded cylindrical pin profile is used. At these specific parameters, the tensile strength is 142 MPa for the threaded cylindrical pin profile and 123 MPa for the taper cylindrical pin profile. The results show that the subsequently created stir zone is entirely dependent on tool rotational speed, traverse speed. Better mixing of the material is observed at higher rotational speed of tool. The shape of the mixing zone is influenced by the shape of the tip. A wider mixing zone is observed when using a tool with a threaded cylinder tip. Conclusions Research shows that aluminum alloy AA8011 can be joined by different pin profiles at different combination of rotational speed and tool traverse speed. A defect-free joint fabricated using a cylindrical threaded tool at a rotation speed of 575 rpm and a traverse speed of 60 mm/min, is characterized by comparatively higher mechanical properties in terms of maximum tensile strength and the joint efficiency. Regardless of the tool pin type, the mechanical properties and joint efficiency was decreased at lower the rotational speed. However, this may be due to some kind of defects. An increase in tensile strength and the joint efficiency was achieved when using a cylindrical threaded pin, which may be due to the formation of fine grains in the stirring zone. References 1. Thomas W.M., Nicholas E.D., Needham J.C., Murch M.G., Temple-Smith P., Dawes C.J. Friction Stir Butt Welding. Patent GB, no. 9125978.8, 1991. 2. Dawes C., Thomas W. Friction stir joining of aluminum alloys. TWI Bulletin, 1995, vol. 6, pp. 124–127. 3. Rhodes C.G., Mahoney M.W., Bingel W.H., Spurling R.A., Bampton C.C. Effects of friction stir welding on microstructure of 7075 aluminium. Scripta Materialia, 1997, vol. 36 (1), pp. 69–75. 4. Liu G., Murr L.E., Niou C.S., McClure J.C., Vega F.R. Microstructural aspects of the friction-stir welding of 6061-T6 aluminum. Scripta Materialia, 1997, vol. 37 (3), pp. 355–361.
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