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In this study, the friction stir spot welding (FSSW) process for the magnesium alloy (AZ91) sheet materials are investigated. Friction stir spot welding (FSSW) is a solidstate welding process and one of the innovative methods to join specifically automotive components. Recently magnesium alloys are promising materials where combination of high strength and low density can be observed to improve vehicle performance and reduce emissions and fuel consumption in structural materials for automotive applications. A finite element model (FEM) established to understand the effect of axial force and rotational speed during the simulation in automotive applications. The FEM investigates the effect of axial force ranging from 1 kN to 8 kN and rotational speeds of 1000 rpm - 4000 rpm. The model analyses the heat flux and the temperature rise that leads defect formation after the process. 4.5 kN, 6 kN and 8 kN axial forces and 3000 rpm- 4000 rpm rotational speeds are evaluated as the critical values in terms of defect and crack formation during the process under specified boundary conditions. Finally, several non-destructive inspection methods are suggested to secure structural integrity after the FSSW process to eliminate the harmful effects of surface and volumetric discontinuities. [ABSTRACT FROM AUTHOR]

A novel method, friction stir spot welding using a consumable sheet (FSSW-C), is introduced here with the aim of joining dissimilar sheets. In this process, faying surfaces of the base materials are kept at a specific gap, and a consumable sheet is placed on the top of the base materials. When the tool progresses into the consumable sheet, the plasticized consumable material gets extruded into the gap and joining occurs between the base materials. The tool never touches the steel base material overcoming the tool wear problem. In the present work, AA6063-T6 and CRCA/IS-513 are the base sheets, and AA6063-T6 is the consumable sheet. The effect of tool rotational speed on the joint formation, interface characteristics, microhardness, temperature evolution, lap shear strength, bend shear strength, and fracture modes have been analyzed. Microstructural zones are also revealed. The rotational speed of 900 rpm is the best choice for FSSW-C of AA6063-T6 and CRCA/IS-513 sheets, keeping 2-mm/min plunge speed, 2-mm plunge depth, 5-s dwell time, and 1.5-mm gap constant. However, additional case studies reveal a plunge depth of 1.5 mm (at 900 rpm) as a better choice due to further lap shear fracture load improvement. [ABSTRACT FROM AUTHOR]

The friction spot welding (FSpW) method was used to weld 2198-T8 Al-Li alloy at rotational speeds of 500 rpm, 1000 rpm, and 1800 rpm. It was shown that the grains in the FSpW joints were transformed from "pancake" grains to fine equiaxed grains by the heat input of welding, and the reinforcing phases of S' and θ were all redissolved into the Al matrix. This leads to a decrease in the tensile strength of the FsPW joint compared to the base material and a change in the fracture mechanism from mixed ductile-brittle fracture to ductile fracture. Finally, the tensile properties of the welded joint depend on the size and morphology of the grains and their dislocation density. At the rotational speed setting of 1000 rpm in this paper, the mechanical properties of welded joints consisting of fine and uniformly distributed equiaxed grains are best. Therefore, a reasonable set of the rotational speed of FSpW can improve the mechanical properties of the welded joints of 2198-T8 Al-Li alloy. [ABSTRACT FROM AUTHOR]

Welding tools of different designs have been used to join friction stir welding 2-mm-thick Al 7075 sheets, to investigate the effect of the tool geometry on the weld performance. Five cylindrical tools with different pin geometries were manufactured from heat-treatable low alloy steel WNr 1.6582/DIN 34CrNiMo6. Additionally, the effect of the welding speed was considered in the work, with six different speeds ranging from 80 mm/min to 300 mm/min. The weld tool rotational speed was kept constant at 1000 rpm and all other parameters were also kept constant in the experiments. The tensile strength was measured to investigate the mechanical properties of the weld. Results were processed with statistical analysis tools, which showed that the mechanical strength was affected by tool geometry as well as welding speed. The weld tool with the highest pin diameter achieved the highest tensile strength. The welding speed affected the tensile strength differently in the different weld tool geometries studied. The highest weld efficiency reported in the tests is 72.20%, achieved with a cylindrical pin weld tool at 250 mm/min. [ABSTRACT FROM AUTHOR]

Friction stir welding equipment was used to weld 3 mm thick 6082 aluminum alloy and T2 copper, through metallurgical microscopy, hardness testings tensile testing, etc.explore the impacts of rotational speed on the organization and mechanical properties of welded joints. The results show that: Intermittent defects always exist at the interface of the joint, alternating distribution of aluminum and copper, and uniform mixing of the two materials; The microhardness distribution of the joint shows that the highest value appears in the weld core area with hardness of 210 HV, aluminum and copper side heat affected zone hardness have decreased, the lowest value for the aluminum side heat affected zone of about 60 H V; with the increase in speedy the tensile strength increases first and then decreases, when the spindle speed of 1 000 r/min, welding speed of 50 mm/min, the optimal weld forming effect, the tensile strength can reach 255 MPa, the fracture shape becomes more uniform with the increase of rotational speed, and the toughness nest increases, showing a stratified distribution. The fracture location is the aluminum copper bond, and the crack extends along the interface defect, showing mixed brittle ductile fracture at low speed and ductile fracture at high speed. [ABSTRACT FROM AUTHOR]

Friction stir lap welding (FSLW) technology was utilized to join 2 mm-thick 2A12-T42 aluminum alloy plates in the current study. Experimental findings demonstrated successful plate joining without welding defects across rotational speeds ranging from 400 to 600 rpm. Higher rotational speeds facilitated ample material flow, resulting in joints that are free of hole defects. The presence of a step can be attributed to a non-synergistic material flow caused by the shoulder and pin. The fracture behavior of the joint is primarily influenced by joint formation factors, such as the distribution of the aluminum cladding (alclad) layer and effective lap width (ELW), as well as the microstructure. The continuous distribution of the alclad layer promotes crack propagation into the nugget zone (NZ). In cases where the ELW is inadequate (at 400 rpm), shear fracture occurs due to crack propagation along the NZ. With an increase in ELW (at 600 rpm), crack propagation is hindered by grain refinement in the NZ, causing the crack to propagate along the weaker thermomechanically affected zone (TMAZ) leading to tensile fracture. [ABSTRACT FROM AUTHOR]

During dissimilar friction stir welding (FSW) of Al-Mg2Si metal matrix composite and AA6061 aluminum alloy, the temperature field and heat generation were investigated using a 3-dimensional computational fluid dynamics (CFD) model and FLUENT software. The simulations were conducted for rotational speeds of 720, 920, and 1120 rpm. The welding experiments were carried out to validate the simulation results. About 70% of the heat is generated at the interface between the shoulder and the workpiece. The maximum temperature is predicted on the advancing side (AS). The difference between the peak temperatures on the AS and the retreating side (RS) is about 115 K. The effect of the rotational speed on the peak temperature is significant. The temperature distribution in the cross sections is asymmetric, which originates from different material velocities on the AS and RS. The peak temperature on the RS develops under the top surface, while the peak temperature on the AS develops on the surface. [ABSTRACT FROM AUTHOR]

The aim of this study was to predict the temperatures on all surfaces of threedimensional models using the ANSYS 15.0 program. Firstly, the temperatures from the welding centre to the edges of the models of two aluminium alloys (AA-7075 & AA-2024) welded by friction stir welding process were perceived. Secondly, the distribution of temperatures from the start of the welding process to its end and the derivation of equations to predict the distribution of temperatures with the time spent in the welding process, along with the distribution of temperatures with the distance from the centre of the welding process were observed at different travel speeds of the welding cart (TS = 20, 40, 60, 100 mm/sec) and different speeds of the welding tool (TRS=900, 1050, 1200 rpm). The results indicate that the temperature increases with the increase in the rotational speed of the welding tool, while the temperature decreases with the increase in the travel speed of the welding cart. Another result is that the temperature distribution is not symmetrical. The highest values are in the welding centre and decrease significantly as the welding centre is moved away, and the highest temperatures can be reached between (75 - 80%) in the welding centre from the melting point of the two aluminium alloys welded together. It was also found that the temperatures increase significantly twenty seconds after the beginning of the welding process and, afterwards, the increase is small, and three equations were derived to predict the temperature distribution. [ABSTRACT FROM AUTHOR]

This study examined the effect of AISI H13 steel-tapered tool on the dissimilar friction stir welding of 7075-T651 and 1200-H19 aluminium alloys. Three mechanical tests which include hardness, tensile strength and impact energy were conducted to study the effect of tilt angle, rotational and welding speeds on the weld integrities, 50 and 175 HV were respectively obtained as hardness values for AA1200- H19 and AA 7075- T651, the hardness values were measured for three selected welding speeds of 30, 60 and 90 mm/min representing low, medium and high at a constant rotational speed of 1500 rpm, a tool tilt angle of 2°.The hardness increases with the welding speed from 81.99 to 98.5 HV as the speed increased from 30 to 60 mm/min and dropped to 77 HV at 90 mm/min.The impact energy increased from 12.9 to 21.4 J with an increase in the welding speed from 30 to 60 mm/min and dropped to 5.4 J at 90 mm/min.The ultimate tensile strength (UTS) increased from 126.04 to 151.54 MPa with an increase in the welding speed from 30–60 mm/min and decreased from 151.54 to 128.37 MPa, the hardness at 1500 rpm and 60 mm/min increased from 70.22 to 98.58 HV with an increase in the tilt angle from 1- 2 ° , a further increase from 2–3 o reduced the hardness from 98.58 to 66 HV, UTS increased from 123.32 to 151.54 MPa as tilt angle increased from 1–2 ° and decreased to 122.2 MPa, the medium tilt angle of 2 ° ,rotational and traverse speeds of 1500 rpm and 60 mm/min respectively gave the highest impact energy of 21.4 J. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is extensively used due to its low processing temperature, cost, and fast operation. The objective of this is research is to determine the optimum rotational and welding speed for welding of Al/Cu butt joint by FSW. FSW is used to produce a butt joint of pure aluminum with pure copper under two conditions; as received, i.e., not annealed, and as annealed. FSW is examined under three different rotational speeds: 910 rpm, 1280 rpm, and 1700 rpm, and each rotational speed is examined at three different welding speeds 16 mm/min, 29 mm/min, and 44 mm/min. The axial and longitudinal welding force components are measured during the welding process. Tensile and hardness tests were done to evaluate the mechanical properties, and the microstructural properties were also examined by XRD, SEM, and an optical microscope. The results showed that the welding force increased and the axial force decreased as the rotational speed increased and the welding speed decreased. Voids, tunnels, and cavities are noticed in case of a low rotational speed and a high welding speed; however, almost defect-free structure obtained at the highest rotational speed examined, i.e., 1700 rpm and the lowest welding speed of 16 mm/min, in case of Al and annealed Cu joint, but in case of non-annealed copper, it was different. It can be concluded that there is an optimal combination between the rotational speed and the welding speed in order to obtain the optimum mechanical and microstructural properties of the Al–Cu-welded joints, and that speed is a function of the material conditions. [ABSTRACT FROM AUTHOR]

In this paper, friction stir welding process of high-density polyethylene was studied. Two tools have been chosen, concave and plate, to explore the influence of the tool on the welding quality of the material. In addition, different parameters, rotational speed and welding speed, were investigated. Tensile tests were performed after welding in order to determine the tensile strength efficiency. The greatest ultimate tensile strength was found for the plates welded by concave shoulder. [ABSTRACT FROM AUTHOR]

In this study, the effect of tool rotational speed on mechanical properties of AA 6082-T6 aluminum alloy was investigated. Different welded joints were produced by using four rotational speed (500, 710, 1000 and 1400 rpm) and constant welding speed at 80 mm/min. Mechanical properties of the welded joints were evaluated by hardness measurement on the transverse section and tensile testing. The experimental results show that the tool rotational speed has a significant effect on weld mechanical properties of joints. [ABSTRACT FROM AUTHOR]

A three-dimensional model was developed based on computational fluid dynamics (CFD) to study the visco-plastic material flow during friction stir welding of AA6061 aluminum alloy and Al-Mg 2 Si composite dissimilar joint. To model the dissimilar joint, the volume of fluid (VOF) method was used. The volumetric equation was defined for the heat which generated through the viscous dissipation. The model was investigated for three rotational speeds of 720, 920 and 1120 rpm. The nugget shape was in good agreement with the corresponding experimental results. The results showed that maximum velocity and strain rate occurred at the top surface of the workpiece and outer edge of the shoulder. Also, peak temperature was obtained at the advancing side. The strain rate at the advancing side and the retreating side was about 975s −1 and 926s −1 , respectively. In a region of the stir zone where material mixing is dominant, the volume fraction of the AA6061 aluminum alloy is 0.4–0.8. [ABSTRACT FROM AUTHOR]

A model is developed to obtain the friction stir welding (FSW) induced stress in structures, which includes the welding process and the cooling process. The characteristics of the welding stress are presented in the analytical results. A detailed numerical simulation is also performed to verify the effectiveness of the proposed model. Numerical results of the welding stress agree well with the welding stress obtained from the analytical model. Then, the effects of process parameters of FSW on the welding stress are studied by using the analytical model. The process parameters involve the depression depth of the welding tool, the rotational speed, and the advancing speed. The calculated results show that the radial stress in the welded structure decreases with the increase of the depression depth. Larger tensile stress appears beneath the tool shoulder with the increase of the rotational speed. Higher advancing speed introduces lower tensile stress in the welded structure. [ABSTRACT FROM AUTHOR]

Friction Stir Spot Welding (FSSW) of AA5052-H32/HDPE/AA5052-H32 sandwich sheets is performed at six different tool rotational speeds to evaluate the optimum range. The mechanical performance, hook formation, grain size, hardness and temperature distribution are evaluated. Lap shear test, cross tension test, peel test and uni-axial tensile test are conducted. A comparative assessment has been made between the bimetallic and the sandwich sheets after FSSW. The optimum rotational speed for joining the sandwich sheet is 1800 rpm and beyond, where the joint strength and extension to failure are found to be acceptable. In hook formation, two hooks are prominently seen in the sandwich sheets, while it is only one hook in the bimetallic sheets. The hook width increases and the hook height decreases with increase in rotational speed. A mechanism has been proposed to explain such phenomenon. The peak temperature increases with increase in rotational speed and it gets reduced in sandwich sheet as compared to bimetallic. The polymer layer takes a part of the heat flux during stirring to reduce the peak temperature in sandwich system. The bimetallic joints are stronger than sandwich sheet joints showing better joint strength and extension at failure in almost all the tests. Joint hardness distribution supports such performance. Nugget pull-out and partial nugget failure are observed during joint failure of sandwich sheets. [ABSTRACT FROM AUTHOR]

This research focused on studying the influence of friction stir welding (FSW) factors - such as the type of the welding tool, the speed of the welding tool and the welding speed - on the impact toughness of the panels made of AA6061 - T6 aluminum alloy sheets with thickness of 3mm. The aluminum alloys have multiple uses in industry, but are quite difficult to be welded by fusion welding processes, including MIG welding, and laser welding. By using a milling machine, it was possible to employ the FSW process, applying four constant welding speeds (800, 1000, 1250, 1600 rpm) and three welding speeds (32, 63, 80 mm/min). Tool pins with square cylindrical and threaded tapered cylindrical profiles were used in the experimental programme. The machined samples were subjected to Charpy V notch impact test at room temperature and the results were compared to the impact energy of the base metal. The results show higher values of the impact energy when the tool pin used has square profile. [ABSTRACT FROM AUTHOR]

The effect of rotational and traverse speeds during dissimilar butt friction stir welding of Al 5083-H321 and 316L stainless steel plates was studied. The macrostructure and microstructure of the joints were examined using optical microscope and scanning electron microscope equipped with energy-dispersive X-ray analysis. The strength of the joints was measured using tensile test. The results showed that with increasing the rotational speed, the tensile strength of the joints increased up to a maximum value and then decreased. In addition, decreasing the traverse speed resulted in higher tensile strength. The 238-MPa maximum value of the tensile strength was achieved at rotational speed of 280 rpm and traverse speed of 160 mm/min. The formation of surface and cross section defects at lower rotational speeds and higher traverse speeds and existence of cracks and microcracks at higher rotational speeds were responsible for the lower tensile strengths of the corresponding joints. In addition, the FeAl intermetallic compound was detected in the interface of the steel particles and Al. [ABSTRACT FROM AUTHOR]

The effect of the rotational speed and dwell time on the joint interface microstructure and tensile-shear strength of friction stir spot welded Al-5083 aluminum/St-12 steel alloy sheets was investigated. Joining of the sheets was performed using an alternative friction stir spot welding (FSSW) process in which the welding tool tip did not penetrate into the lower steel sheet. Rotational speeds of 900 and 1100 rpm were applied in association with the dwell times of 5 to 15 s to weld the samples. Thermal history was recorded during the joining process. Interfacial microstructure, formation of intermetallic compounds (IMCs) at the joint interface and the fracture locations were studied using stereo, optical and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The used alternative process was successful to join the sheets. For both of the applied rotational speeds, there were optimum dwell times (10 and 12 s for the rotational speeds of 1100 and 900 rpm, respectively) to reach the maximum failure loads. The increasing trend of the strength as a function of the dwell time was related to the formation of a thin intermetallic (IM) layer at the joint interface. The decreasing trend was attributed to the formation of a relatively thick IM layer at the joint interface as well as the grain growth of aluminum at the exit-hole periphery where the final fracture occurred. The IM reaction layer thickness of 2.3 μm was found to be a critical thickness. Compared to the rotational speed of 1100 rpm, stronger joints were achieved by application of 900 rpm rotational speed. [ABSTRACT FROM AUTHOR]

This article reports the results of applying the response surface methodology to evaluate the tensile strength in joints obtained by the process of friction-stir welding (SFA), depending on the speed of rotation of the tool and welding speed. The joints were welded with a conventional milling machine capable DECKEL FP4M 3 HP and a threaded cylindrical pin. In the microscopic images clearly shows the effect of the dynamic recrystallization in the stirred zone (ZA). Microhardness profiles show the typical shape of W and with metallography performed on samples tested at tension that Heat Affected Zone (HAZ) is the weakest microstructural areas of the join. The greater tensile strength of the welded joints of the aluminum alloy AA 6261-T5 by SFA (191.63 MPa) was obtained using the threaded cylindrical pin, a welding speed 315 mm / min and a rotation speed of 1600 rpm. [ABSTRACT FROM AUTHOR]

Welding parameters like welding speed, rotation speed, plunge depth, shoulder diameter etc., influence the weld zone properties, microstructure of friction stir welds, and forming behavior of welded sheets in a synergistic fashion. The main aims of the present work are to (1) analyze the effect of welding speed, rotation speed, plunge depth, and shoulder diameter on the formation of internal defects during friction stir welding (FSW), (2) study the effect on axial force and torque during welding, (c) optimize the welding parameters for producing internal defect-free welds, and (d) propose and validate a simple criterion to identify defect-free weld formation. The base material used for FSW throughout the work is Al 6061T6 having a thickness value of 2.1 mm. Only butt welding of sheets is aimed in the present work. It is observed from the present analysis that higher welding speed, higher rotation speed, and higher plunge depth are preferred for producing a weld without internal defects. All the shoulder diameters used for FSW in the present work produced defect-free welds. The axial force and torque are not constant and a large variation is seen with respect to FSW parameters that produced defective welds. In the case of defect-free weld formation, the axial force and torque are relatively constant. A simple criterion, (∂ τ/∂ p) > (∂ τ/∂ p) and (∂F/∂ p) > (∂F/∂ p), is proposed with this observation for identifying the onset of defect-free weld formation. Here F is axial force, τ is torque, and p is welding speed or tool rotation speed or plunge depth. The same criterion is validated with respect to Al 5 xxx base material. Even in this case, the axial force and torque remained constant while producing defect-free welds. [ABSTRACT FROM AUTHOR]

In this study, rolled plates of AA 2198 T3 aluminium alloy are friction-stir welded in butt configuration varying two fundamental process parameters: rotational and welding speeds. Two sets of empirical models based on regression analysis are developed. The first one predicts the stationary values of the in-plane and downwards forging welding forces in dependence of the process parameters under investigation. The second one predicts the mechanical strength, in particular yield and tensile strength, of the friction-stir welded joints as function of the same parameters. For the development of the empirical models, two 3 full factorial designs are used: one having the stationary values of the welding forces and the other having the yield and tensile strength as observed responses, respectively. Statistical tools such as analysis of variance, F tests, Mallows' C, coefficient of determination etc. are used to build and to validate the developed models. By using the desirability function approach, the optimum process parameters to simultaneously obtain maximum possible yield and tensile strength are found within the investigated range. The developed models can be effectively used to predict the stationary forces and the mechanical proprieties of the joints at 95% confidence level. [ABSTRACT FROM AUTHOR]

Abstract: Friction stir welding (FSW) is a solid state welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds. [Copyright &y& Elsevier]

Abstract: AA2219 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio. Compared to the many fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. The welding parameters and tool pin profile play a major role in deciding the weld quality. In this investigation an attempt has been made to understand the influences of rotational speed and pin profile of the tool on friction stir processed (FSP) zone formation in AA2219 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different tool rotational speeds. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square tool pin profile produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles. [Copyright &y& Elsevier]