One of the advantages of friction stir welding (FSW) is reduced energy consumption as compared to arc welding processes. This advantage has been predicted and qualitatively established. However, a quantitative analysis based on energy measurements during the processes and how to equitably compare them is missing. The objective of this work is to quantitatively compare the energy consumption associated with the creation of full-penetration welds in aluminum 6061-T6 workpieces by FSW and gas metal arc welding (GMAW) processes. The workpiece thicknesses for the two processes (5-mm-thick for FSW and 7.1-mm-thick for GMAW) are chosen such that the maximum tensile force sustained by the joints during tensile testing is similar. This accounts for material saving due to the higher ultimate tensile strength resulting from FSW. The energy consumed for any pre-processes, the welding processes, and post-processes was measured. Finally, a life cycle assessment (LCA) approach was used to determine and compare the environmental impact of FSW and GMAW. For the welding parameters used in this study joining by FSW consumes 42% less energy as compared to GMAW and utilizes approximately 10% less material for the design criteria of similar maximum tensile force. This leads to approximately 31% less greenhouse gas emissions for FSW as compared to GMAW. Both, the lower energy consumption during FSW, and involved pre and post processes contributed in the overall energy reduction.

Comparison of energy consumption and environmental impact of friction stir welding and gas metal arc welding for aluminum

In this study, the effects of tool rotational and traverse speeds on the mechanical properties and the microstructure of the friction stir welded joints from Al 5086-H34 were studied. Insufficient heat generation and inadequate metal transportation at very low rotational speed and high turbulence in the plasticized metal at very high rotational speed emerged tunnel and worm hole defects into the weldment. It was discovered that as rotational and traverse speed increased, the average grain size of the weldment decreased due to more dynamic recrystallization and amplified stirring effect. An increase in the rotational speed increased the ultimate tensile strength and microhardness of the specimens. At the best welding condition, by employing the rotational and traverse speeds of 1250 rpm and 80 mm/min, respectively, 51 % enhancement in the elongation and 8 % increase in the microhardness of the welded samples were obtained. Moreover, the ultimate tensile strength of this welded joint reached to 85 % of the base metal.

Study on the effects of friction stir welding process parameters on the microstructure and mechanical properties of 5086-H34 aluminum welded joints

The never ending appetite of the mankind to produce more and more competitive products results in continuous development of newer and newer manufacturing processes. One of such a kind, a solid stat...

Friction stir welding of aluminium alloys: An overview of experimental findings – Process, variables, development and applications:

In the present study, the effect of tool rotational speed on residual stress, microstructure, and tensile properties of friction stir welded AA 6061-T6 was investigated. AA 6061-T6 plates with a thickness of 16 mm were friction stir welded using three different tool rotational speeds of 500, 700, and 900 rpm and a constant welding speed of 120 mm/min. The results indicate that the longitudinal residual stress distribution is an M-shaped distribution in the transverse direction; in weld region, the tensile longitudinal stress in the advancing side is larger than that in the retreating side. With increasing rotation speed, the values of the tensile longitudinal residual stresses increased slightly, the peak tensile longitudinal stresses appear at the edge of the shoulder in the AS of the joints, and the maximum value of tensile longitudinal residual stress was 153 MPa with the rotation speed of 900 rpm which reaches up to 55 % of the yield strength of AA 6061-T6. Meanwhile, only the appearance of welded joint with 700 rpm is smooth. The grain size in WNZ grows up with increasing the rotation speed. The microhardness variation is determined by microstructure evolution, and the average microhardness decreases with increasing the rotation speed. The welded joint with the rotation speed of 700 rpm performs the maximum tensile strength of 236 MPa which is 76 % of the base material strength.

Effect of tool rotational speed on residual stress, microstructure, and tensile properties of friction stir welded 6061-T6 aluminum alloy thick plate

Influence of tool rotation speeds on mechanical and morphological properties of friction stir processed nano hybrid composite of MWCNT-Graphene-AZ31 magnesium

Effect of small tool pin profiles on microstructures and mechanical properties of 6061 aluminum alloy by friction stir welding

The present work is an experimental comparison between the friction stir welding (FSW) and the conventional gas metal arc welding (GMAW) in joining of Al alloys. Two sets of 3 mm thick aluminum strip pairs were friction stir welded in a regular butting joint configuration. Two rotational speeds of 1750 rpm and 2720 rpm were utilized to perform the FSW process. The axial force and the transverse speed were kept constant at 6.5 KN and 45 mm/min, respectively. Cylindrical tool shoulder and pin geometry were selected. Strip pairs of other similar sets were butt jointed using the conventional GMAW. The welding quality, power input, and macrostructure and microstructure of the butted joints were examined. The types of the fumes and the amount of the released gases were measured and compared. The results showed that the solid state FSW is green, environment-friendly, and of superior welding properties compared to the conventional GMAW.

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Advantages of the Green Solid State FSW over the Conventional GMAW Process

In the present study, four pairs of 6061 aluminium alloy workpieces with different surface roughness were prepared for welding. The friction stir welding (FSW) technique was used for a butt-joint configuration of a single pass. The influence of different surface roughness of the workpieces coincided with a small welding tool shoulder diameter, and the tool pin was examined. The results demonstrated that spherical nano-sized grains of the joints were produced. The mechanical properties of the joints were significantly better at the least possible workpiece surface roughness. The experimental results also indicated that the tensile strength of FSW 6061 aluminium alloy was notably affected by joining at the different workpiece surface roughness selected. However, an improvement of the Vickers microhardness in the heat affected zone (HAZ) was also observed. The microhardness in the nugget zone (NZ) for the welded joint fabricated at the lowest value of the workpiece surface roughness was higher than that of the base metal (BM). The fractural surface of the cross-section of the tensile specimens has a gradient to change from brittle fracture to ductile fracture.

The influence of the surface roughness on the microstructures and mechanical properties of 6061 aluminium alloy using friction stir welding

Friction stir welding is a solid state green welding technique. Its key benefit is to allow welding of aluminum that cannot be readily done by fusion arc welding. In this study, two pure aluminum strips of 2mm thick were friction stir welded together. For all welding pairs, three rotational speeds of 1000, 1500 and 2000 rpm were used. The traverse speed, axial force and tool geometry were kept constant. Parameters optimization based on the results of the micrographic, macrographic, microhardness and tensile strength, indicated that sound joints with the best mechanical and microstructural properties can be obtained at rotational speed of 1500 rpm and welding transverse speed of 60 mm/min. Microscopic examination and local mechanical properties analysis suggested that mechanical mixing is the major material flow mechanism in the formation of the nugget stirred zone.

The Effect of Rotational Speed on Flow Behavior and Weld Properties in Friction Stir Welding of Pure Aluminum

After 10 vol. % SiC particles from the welding volume were inserted into the joint line, the mechanical properties of friction stir-welded joints were assessed. During the Friction Stir Welding (FSW) process, three different rotational speeds (1300, 1750, and 2000 rpm) were used. Field Emission Scanning Electron Microscopy (FESEM) was used to examine the microstructure across the Stir Zone (SZ), revealing a banded structure between the particle-rich and particle-free portions of the SiCp. When the joint was constructed at 1750 rpm, it displayed better mechanical properties. Because of the presence of SiCp, the Ultimate Tensile Strength (UTS) was enriched by 79.6% at 1750 rpm. Because of the pinning effect and larger nucleation sites caused by the SiC powder, this strength significantly increased. Furthermore, the hardened particle powder cracked the initial grains. When compared to the SiC-free sample, the SiC-rich sample had higher ductility at 1750 rpm. Finally, the fracture surface showed a good agreement with the equivalent ductility marks.

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Hasan I. Dawood

Papers

Effect of small tool pin profiles on microstructures and mechanical properties of 6061 aluminum alloy by friction stir welding

Advantages of the Green Solid State FSW over the Conventional GMAW Process

The influence of the surface roughness on the microstructures and mechanical properties of 6061 aluminium alloy using friction stir welding

The Effect of Rotational Speed on Flow Behavior and Weld Properties in Friction Stir Welding of Pure Aluminum

Microstructure, thermal, and mechanical properties of friction stir welded 6061 aluminum alloy with 10% SiCp reinforcement