Ultrasonic assisted second phase transformations under severe plastic deformation in friction stir welding of AA2024

Елисеев, А. А.; Калашникова, Т. А.; Gurianov, D. A.; Рубцов, В. Е.; Ivanov, A. N.; Колубаев, Е. А.

doi:10.1016/j.mtcomm.2019.100660

Cited by 15 publications

(8 citation statements)

References 20 publications

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“…The results show that the deviations of the transfer layer thickness are quite small and are within 6 μm. However, there is a clear dependence of these deviations on the load, which was previously predicted [10]. The diagram resembles a Gaussian or parabola, and its maximum values correspond to the feed to rotation rate ratio during processing at the load 2650-2700 kg.…”

Section: Influence Of Load On the Transfer Layersupporting

confidence: 65%

“…However, the transfer layer thickness can be inconsistent with the given formula or can depend on conditions being neglected in it. For example, in [10] we revealed a variation in the transfer layer thickness when friction stir welding of 2024 aluminum alloy is accompanied by ultrasonic vibrations transmitted into the workpiece. Ultrasonic vibrations activate the acoustoplastic effect, which, in this context, means deformation intensification, making changes in adhesive-cohesive transfer possible.…”

Section: Adhesion-cohesion Concept Of Mass Transfermentioning

confidence: 96%

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Material Transfer by Friction Stir Processing

Елисеев

Калашникова

Филиппов

et al. 2020

Springer Tracts in Mechanical Engineering

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Mechanical surface hardening processes have long been of interest to science and technology. Today, surface modification technologies have reached a new level. One of them is friction stir processing that refines the grain structure of the material to a submicrocrystalline state. Previously, the severe plastic deformation occurring during processing was mainly described from the standpoint of temperature and deformation, because the process is primarily thermomechanical. Modeling of friction stir welding and processing predicted well the heat generation in a quasi-liquid medium. However, the friction stir process takes place in the solid phase, and therefore the mass transfer issues remained unresolved. The present work develops the concept of adhesive-cohesive mass transfer during which the rotating tool entrains the material due to adhesion, builds up a transfer layer due to cohesion, and then leaves it behind. Thus, the transfer layer thickness is a clear criterion for the mass transfer effectiveness. Here we investigate the effect of the load on the transfer layer and analyze it from the viewpoint of the friction coefficient and heat generation. It is shown that the transfer layer thickness increases with increasing load, reaches a maximum, and then decreases. In so doing, the average moment on the tool and the temperature constantly grow, while the friction coefficient decreases. This means that the mass transfer cannot be fully described in terms of temperature and strain. The given load dependence of the transfer layer thickness is explained by an increase in the cohesion forces with increasing load, and then by a decrease in cohesion due to material overheating. The maximum transfer layer thickness is equal to the feed to rotation rate ratio and is observed at the axial load that causes a stress close to the yield point of the material. Additional plasticization of the material resulting from the acoustoplastic effect induced by ultrasonic treatment slightly reduces the transfer layer thickness, but has almost no effect on the moment, friction coefficient, and temperature. The surface roughness of the processed material is found to have a similar load dependence.

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Section: Influence Of Load On the Transfer Layersupporting

confidence: 65%

Section: Adhesion-cohesion Concept Of Mass Transfermentioning

confidence: 96%

Material Transfer by Friction Stir Processing

Елисеев

Калашникова

Филиппов

et al. 2020

Springer Tracts in Mechanical Engineering

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“…Larger and elongated particles are located at grain junctions; small equiaxed particles are most often located inside the grains. As was shown in previous papers [ 16 ] and other works [ 17 ], the volume fraction of these particles is often inversely proportional to the volume fraction of coherent and semi-coherent particles due to the limited amount of alloying elements in the alloy. The incoherent particles appear as bright contrast in the SEM image ( Figure 6 ).…”

Section: Resultsmentioning

confidence: 70%

Gradient Structure of the Transfer Layer in Friction Stir Welding Joints

2022

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Despite a thirty-year history of friction stir welding, some basic aspects still remain unclear. In particular, questions arise about mass transfer and the formation of transfer layers. It is not clear why there are visible boundaries between the layers. The structure of the transfer layer has been studied very little. These issues are not considerably important from the viewpoint of obtaining high-quality welds, but they can help to a better understanding of the welding process. In this paper, the structural evolution in the transfer layer of 2024 aluminum alloy welds produced under various loads and with ultrasonic assistance is discussed. Structural studies revealed a gradient structure in the transfer layer. The grain size, the volume fraction and size of large intermetallic particles decrease towards the center of the layer, while the volume fraction of semi-coherent secondary particles increases. As a result, the microhardness is higher in the center of the transfer layer. A mass transfer mechanism is proposed based on the experimental results: the rotating tool transfers the material back layer by layer during welding; the contacting layers rub against each other and generate heat, due to which the structure at the layer boundary changes. With increasing axial force on the tool, the grain size also increases due to higher heat generation. Ultrasound has almost no effect on the grain structure, but it reduces the volume fraction and size of secondary particles and microhardness.

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“…Using this device for butt joint experiments on 6061-T6 and 2024-T4 aluminum alloys, it was discovered that applying ultrasonic vibration directly to the workpiece surface might improve the welded joint's mechanical and fluidity properties, therefore expanding the process window and increasing the surface forming quality of aluminum alloy welding. In 2017, A.A. Eliseev et al [11] introduced a new ultrasonic loading method for ultrasonic impact treatment of the workpiece that uses a magneto-strictive transducer rigidly mounted on the free edge of the workpiece to be welded and an adaptive ultrasonic generator that provides optimal vibration transfer efficiency at 21-23 kHz. At present, scholars involved in ultrasonic-assisted friction stir welding research mainly include the influence of ultrasound on the mechanical properties and microstructure of the weld, the mechanism of action of ultrasound, etc.…”

Section: Introductionmentioning

confidence: 99%

“…Eliseev's method, mentioned as literature [11] above, involves ultrasonic vibration applied to the workpiece to be welded. Its advantage is that the stirring tool structure changes have less impact on a variety of materials and have universal adaptability.…”

Section: Introductionmentioning

confidence: 99%

Effect of Ultrasonic Vibration in Friction Stir Welding of 2219 Aluminum Alloy: An Effective Model for Predicting Weld Strength

Xue

Zhou

2022

Metals

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Friction stir welding (FSW) is today used as a premier solution for joining non-ferrous metals, although there are many limitations in its application. One of the objectives of this study was to propose an innovative welding technique, namely ultrasonic-assisted friction stir welding (UAFSW) with longitudinal ultrasonic vibration applied to the stirring head. In this paper, UAFSW mechanical properties and microstructure analysis were performed to demonstrate that the fluidity of the weld area was improved and the strengthened phase organization was partially preserved, due to the application of ultrasonic vibration. The addition of 1.8 kW of ultrasonic vibration at 1200 rpm and 150 mm/min welding parameters resulted in a 10.5% increase in the tensile strength of the weld. The ultimate tensile strength of 2219 aluminum alloy UAFSW was analyzed and predicted using mathematical modeling and machine learning techniques. A full factorial design method with multiple regression, random forest, and support vector machine was used to validate the experimental results. In predicting the tensile behavior of UAFSW joints, by comparing the evaluation metrics, such as R2, MSE, RMSE, and MAE, it was found that the RF model was 22% and 21% more accurate in the R2 metric compared to other models, and RF was considered as the best performing machine learning method.

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Ultrasonic assisted second phase transformations under severe plastic deformation in friction stir welding of AA2024

Cited by 15 publications

References 20 publications

Material Transfer by Friction Stir Processing

Material Transfer by Friction Stir Processing

Gradient Structure of the Transfer Layer in Friction Stir Welding Joints

Effect of Ultrasonic Vibration in Friction Stir Welding of 2219 Aluminum Alloy: An Effective Model for Predicting Weld Strength

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