Stir Spot Welded Aluminum Alloy Research Articles

Influence of rotational speed on the electrical and mechanical properties of the friction stir spot welded aluminium alloy sheets

AbstractAn efficient and productive joining technique to weld aluminium has become a priority challenge for promoting the use of aluminium in the electrical industry. One of the challenges is to obtain welds with superior mechanical properties with the consistent quality of weld surface as well as low electrical resistance. In this paper, the influence of rotational speed during the friction stir spot welding of AA 5754-H111 was studied to analyse the mechanical and electrical properties of the welds. The results from two rotational speeds (1000 rpm and 4500 rpm) are presented and compared to the base material. It was observed that the samples welded at 1000 rpm showed a higher average shear failure load (~ 1.1 kN) compared to the samples welded at 4500 rpm (~ 0.94 kN). The microhardness of the samples welded at 1000 rpm was higher than that of the base material, while the microhardness of samples welded at 4500 rpm was lower. It was also found that the friction welded sheets, regardless of the rotational speed used, showed increased electrical resistance compared to the base material, albeit this increase for the samples welded at 1000 rpm was about 42%, compared to samples welded at 4500 rpm where this increase was just 14%.

Impact of post weld heat treatment on mechanical and microstructural properties of underwater friction stir spot welded 6061 aluminium alloy

A lap joint of 6061 aluminium alloy using Friction stir spot welding is produced in two different mediums (air and water) at three different rotational speed to study the effect of medium on the joint properties. Joint properties were analysed by using mechanical and microstructural observation. With the goal of improving the strength of the fabricated joints, weldments are subjected to various heat treatment processes (post-weld ageing). The joint properties were analysed using a combined study of micrographs and micro-hardness results. Findings can be deduced that the properties of water-cooled joints got enhanced to a greater extent relative to the joints produced in air. Different processing conditions have a distinct effect on the hardness distribution with a common highest hardness region found to be located in a heat-affected zone. Additionally, it was observed that artificial ageing at 180 ℃ for 12 h is a feasibly fast and cost-efficient process for ageing PWHT in the industrial arrangement. This paper reports on studies of the outcome of post-weld heating of the spot-welded AA6061 aluminium alloy and its effect on the characteristics of friction stir spot welded aluminium alloy 6061 joints.

Microstructure and joint strength of friction stir spot welded aluminum alloy sheet/plated steel sheet joints

Microstructure and joint strength of friction stir spot welded aluminum alloy sheet/plated steel sheet joints

Load level prediction system model of friction stir spot welded aluminium alloy using support vector machine

The cost and efficiency of experiment and test are still a major issue in manufacturing especially in welding. In this study, a machine learning technique i.e. support vector machine (SVM) was applied to develop a load level prediction system of friction stir spot welded joint aluminium alloy AA5052-H112. This load level prediction system model was proposed based on three levels of load group of the welded joint. Experimental works in friction stir spot welding was conducted on samples specimens of AA5052-H112 2mm thick overlap joint based on 27 combinations of governed parameters i.e. spindle speed, tool depth, and dwell time. Mechanical testing of tensile shear load was then carried out to those specimens to obtain 27 loads data to form the SVM classifier. These data were required for pattern classification and model development via training and testing the proposed prediction system. The result obtained via training and testing showed the classification of load data produced by the proposed system, matched to the required load level with the 100%. This study proved that the proposed load level prediction system offered a useful tool to predict the load level of friction stir welded joint aluminium alloy AA5052-H112 by using respected parameters without required experiments and tests.

Microstructure and mechanical properties of friction stir spot welded aluminum alloy joints

Microstructure and mechanical properties of friction stir spot welded aluminum alloy joints

Microstructures and Mechanical Properties of Friction Stir Spot Welded Aluminum Alloy AA2014

Friction stir spot welding (FSSW) is a relatively recent development, which can provide a superior alternative to resistance spot welding and riveting for fabrication of aluminum sheet metal structures. In the current work, FSSW experiments were conducted in 3-mm thick sheets of aluminum alloy 2014 in T4 and T6 conditions, with and without Alclad layers. The effects of tool geometry and welding process parameters on joint formation were investigated. A good correlation between process parameters, bond width, hook height, joint strength, and fracture mode was observed. The presence of Alclad layers and the base metal temper condition were found to have no major effect on joint formation and joint strength. Friction stir spot welds produced under optimum conditions were found to be superior to riveted joints in lap-shear and cross-tension tests. The prospects of FSSW in aluminum sheet metal fabrication are discussed.

Joint Interface Morphology of Friction Stir Spot Welded Aluminum Alloy Sheets and Plated Steel Sheets

Friction stir spot welding (FSSW) was applied to lap joining of aluminum alloy sheets and steel sheets. A 1.2 mm-thick non-plated carbon steel sheet and plated steel sheets with zinc alloy (ZAM), pure zinc (GI), zinc alloy including Fe (GA) and Al-Si alloy (AS) were prepared. The melting temperature of the plated layer is 330, 420, 880 and 640°C, respectively. A 1.1 mm-thick 6022 aluminum alloy sheet was overlapped on the steel sheet. A rotating tool was inserted from the aluminum alloy sheet side and the probe tip was kept at the position of 0.2 mm above the lapped interface for 3 seconds. For ZAM and GI, original plated layers were removed from the interface and intermediate layers were formed at the joint interface. This is because the melting temperature of the plated layer was lower than the interface temperature under the rotating probe tip during the FSSW. In contrast to that, the partial original plated layer remained after welding, and additional layer formed at the plated layer /aluminum alloy interface for GA. For AS, Al-Fe intermetallic compound layer, which was formed at the original Al-Si alloy plated steel surface remained.

Effects of process time and thread on tensile shear strength of Al alloy lap joint produced by friction stir spot welding

In automotive applications, friction stir spot welding (FSSW) has been practically used in the construction of aluminium car bodies. In this study, the weld strength and factors governing the weld strength in the friction stir spot welded aluminium alloy 6061-T6 were examined. The weld strength increased with the process time during FSSW up to 3 s, beyond which it decreased. The fracture path changed from the lapped interface into the shoulder edge as the process time increased, and the maximum strength was obtained at the process time when the transition of the fracture path occurred. The cross-sectional microstructure depended on the threads on the probe surface, i.e. the elliptical zone was formed in the stir zone by the threads, but an effect of the thread on the weld strength was hardly found. The present study suggests that the weld strength was strongly related to the size of the well-consolidated region, which was larger than the elliptical zone observed in the vicinity of the exit hole.

Comparison of fatigue behaviour between resistance spot and friction stir spot welded aluminium alloy sheets

Tensile shear fatigue tests have been performed using resistance spot welded (RSW) joint and friction stir spot welded (FSSW) joint of aluminium alloy sheets. When fatigue strength was characterised in terms of applied load, RSW joint showed higher fatigue strength than FSSW joint in the entire load range, while the fatigue strength normalised with respect to the nugget area was higher in FSSW joint than in RSW joint. Friction stir spot welded joint exhibited a very small scatter of fatigue life compared with RSW joint, indicating that FSSW is a very stable and reliable joining method. Macroscopic fatigue fracture modes were similar in both joints: nugget shear fracture in high applied load region and parent sheet fracture in low applied load region. It was indicated that geometrical factors around the weld zone played a dominant role in determining the fatigue strength and fracture mechanism of the joints.

Effect of tool geometry on static strength of friction stir spot-welded aluminum alloy

Friction stir spot welding is performed on 5083 Al alloy using tools with a conventional cylindrical pin and the proposed triangular pin. Partial metallurgical bond (called as ‘hook’) is formed in the weld region between the overlapped metal sheets. The tool-pin geometry significantly affects the hook shape. Under the same process condition, welds made with the cylindrical pin have a continuous hook which bypasses the stir zone and points downward towards the weld bottom. By contrast, for welds made with the triangular pin, the hook is directed upwards and then arrested at the periphery of the stir zone. The difference in the hook shape could be attributed to the asymmetric rotation of the triangular pin that may cause the material in the vicinity of the pin to move back and forth in the radial direction resulting in the hook being broken-up (dispersed) in the stir zone. In addition, the triangular pin results in a finer grain structure in the stir zone compared to the cylindrical pin. Static strength of welds made with the triangular pin is twice that of welds made with the cylindrical pin, which is attributed to the finer grain size as well as tensile failure mode as a result of the arrested hook.

摩擦攪拌点接合で得られたアルミニウム合金重ね継手の引張せん断強度に及ぼす接合時間とねじの影響

Friction Stir Spot Welding (FSSW) has been practically used to the construction of aluminum car-body in the automotive application. In this study, the weld strength and factors governing the weld strength in friction stir spot welded aluminum alloy 6061-T6 was examined. The weld strength increased with the process time during FSSW up to 3 s, beyond which it decreased. The fracture path changed from the lapped interface into the shoulder edge as the process time increased, and the maximum strength was obtained at the process time when the transition of the fracture path occurred. The cross-sectional microstructure depended on the threads on the probe surface, i.e. the elliptical zone was formed in the stir zone by the threads, but effect of the thread on the weld strength was hardly found. The present study suggests that the weld strength was strongly related with size of the well-consolidated region which was larger than the elliptical zone observed in the vicinity of the exit hole.