Mechanical properties and welding signal of aluminium alloy aa1100 welded using Bobbin Friction stir welding

• Main Author: Mohd Nasir, Siti Noor Najihah
• Format: Thesis
• Language: English; English
• Published: 2022
• Subjects: T Technology (General); TS Manufactures
• Online Access: http://eprints.utem.edu.my/id/eprint/26972/1/Mechanical%20properties%20and%20welding%20signal%20of%20aluminium%20alloy%20aa1100%20welded%20using%20Bobbin%20Friction%20stir%20welding.pdf; http://eprints.utem.edu.my/id/eprint/26972/2/Mechanical%20properties%20and%20welding%20signal%20of%20aluminium%20alloy%20aa1100%20welded%20using%20Bobbin%20Friction%20stir%20welding.pdf; http://eprints.utem.edu.my/id/eprint/26972/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=122232
• Institution: Universiti Teknikal Malaysia Melaka

Joining Aluminium alloys using fusion welding is challenging due to Aluminium has low melting point and high oxidation layer especially when dealing with AA1100 which has high Aluminium contents. This material mostly applied in industrial application such as fin stock, aeroplane parts and sheet metal work. Fusion welding processes produced high heat which cause material difficult to weld and gives out by-product waste like toxic gas, fume and arc formation. As an alternative, Aluminium alloys can be joined via Bobbin Friction Stir Welding (BFSW). However, BFSW that use a double-sided tool produced higher heat compared to the single sided tool. Secondarily, issues on having minimum literature regarding process signal in term of heat, welding force and energy utilisation has not widely discussed including various materials and its optimisation. Therefore, this study aims to assess feasibility study performance on fixed gap bobbin tool usage in welding of AA1100, evaluate the mechanical properties of the welded AA1100 and to suggest optimum parameters for welding AA1100. Current, temperature and welding forces were measured during the BFSW as signal processing. Findings shows current measurement increased remarkably at average value of 12.1A (5.02kW) and settles to a steady state with about 49.38% of power consumption at weld phase before dropping to average value of 1.6 A (663 W). For temperature measurement, peak temperature of every embedded thermocouple was higher on advancing side (AS) rather than the retreating side (RS). The highest temperature was exhibited by the weld sample processed under spindle speed of 950 rpm and welding speed of 130 mm/min on the AS of the weld with the value of 397 ◦C. For welding force measurement, all force plots depicted a high fluctuation at beginning of the plot following with stable peak variation and had small fluctuation at the end of the plot. The highest torque was 135.18 kNm in Fx direction and 107.55 kNm in Fy direction at spindle speed of 750 rpm and welding speed of 170 mm/min. The highest average hardness in SZ was 35.6 HV for weld sample processed under spindle speed of 950 rpm and welding speed of 150 mm/min. The weld strength was 102.860 MPa achieved by weld produced at spindle speed of 950 rpm and welding speed of 130 mm/min whereas the lowest tensile strength was 92.139 MPa under the same welding speed and spindle speed of 750 rpm. For microstructure analysis, the SZ region has smaller equiaxed recrystallized grains with rough edges while the TMAZ region revealed elongated grains. The HAZ region depicted elongated grain with unclear grain boundary. The grain size in SZ increase from 9.6 ± 0.2μm to 12.3 ± 0.1μm when spindle speed increased. The tensile strength before the optimisation was 102.86 MPa and improved at 103.19 MPa as suggested by the FCCD. On the other hand, for maximum average hardness at SZ region, the hardness before the optimisation was 35.6 HV and optimum value suggested by FCCD was 36.01 HV. Validation test of the transverse tensile strength and average hardness at the SZ region were 102.36 MPa and 35.42 HV respectively which give the experimental error of 0.8 % and 1.64 %. AA1100 weld has been optimized which higher spindle speed and slow welding speed provide strong weld joint.