Influence of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution and material mixing during FSW of AA6063 aluminum alloy sheets

Influence of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution and material mixing during FSW of AA6063 aluminum alloy sheets | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Influence of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution and material mixing during FSW of AA6063 aluminum alloy sheets Radmir Adilbekovich Rzaev, Nafis Fanisovich Khayretdinov, Dilara Byazitovna Kabirova, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6927846/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Sep, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract The aim of the work was to investigate the effect of the scroll groove depth and welding pressure on the temperature distribution and material mixing in pinless friction stir butt welding of AA6063 aluminum alloy sheets using the method of mathematical modeling. The tool was a shoulder with two scroll grooves, the depth of which varied from 0 to 0.5 mm with a step of 0.1 mm. Modeling showed a significant effect of the groove depth on the temperature distribution and the formation of surface defects. The maximum temperature and the largest area of strong heating were observed at a groove depth of 0.2 mm, which ensured a complete connection of sheets at a welding pressure of 12.5 MPa. The effect of the groove depth on the magnitude and distribution of temperature was explained based on the concepts of the action of two material heating mechanisms: 1) frictional heating and 2) heating from plastic deformation of the material volume. Strong and uniform heating at a groove depth of 0.2 mm was achieved by summing the heat from frictional heating and heat from plastic deformation. A full-scale experiment using a shoulder with a scroll groove depth of 0.2 mm showed good agreement with the simulation results. Pinless friction stir welding mathematical modeling shoulder geometry aluminum alloy welding pressure Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1 Introduction Friction stir welding (FSW) was invented and patented in 1991 by TWI [ 1 , 2 ] and has since been widely used in manufacturing. FSW has proven to be much more efficient and provide higher mechanical properties than previously used welding methods such as metal inert gas (MIG) welding [ 3 ], tungsten inert gas (TIG) welding [ 4 , 5 ], laser welding [ 6 , 7 ], and resistance welding [ 8 ]. The FSW tool consists of two parts – a shoulder and a pin. According to various estimates, 75–80% of the heat flow is generated at the shoulder-workpiece boundary, and the remaining 20–25% is released at the pin-workpiece boundary [ 9 – 12 ]. When applied to aluminum alloys, FSW allows joining workpieces up to 76.2 mm thick [ 13 ]. The disadvantage of using a tool consisting of a shoulder and a pin for thin sheets is the presence of a depression from the pin at the end of the weld, the so-called weld keyhole, which worsens the mechanical properties. To eliminate this defect, flat shoulders without a pin were used in a number of studies. In this case, the heat flow during stirring was created only by the friction force at the shoulder-workpiece interface. Zhang et al. [ 14 ] used a simple cylindrical shoulder with a diameter of 15 or 20 mm to weld sheets of technically pure aluminum with a thickness of 1.8 mm in a friction stir lap welding manner. The absence of the pin had little effect on the heating behavior and cross-sectional profile of the joint after welding. It was also shown that the forging effect can be enhanced by tilting the tool, which is necessary to enhance the contact between the top and bottom sheets. Forcellese et al. [ 15 ] investigated the influence of FSW parameters, tool geometry and size on the macro - and micromechanical properties of joints in 1.5 mm thick AZ31 magnesium alloy sheets. Two tools with shoulder diameters of 8 and 19 mm were used, each manufactured in pin and pinless versions. It was found that the shoulder diameter plays an important role in pinless FSW: an increase in the shoulder diameter from 8 to 19 mm led to an increase in the strength and ductility of the welded joints. Kim et al. [ 16 ] obtained satisfactory properties of a butt joint of 0.5 mm thick 430M2 ultra-thin ferritic stainless steel sheets after FSW using a pinless tool made of WC-Co carbide. The pinless flat shoulder has also been applied for FSW of dissimilar alloys. Thus, Simoncini et al. [ 17 ] successfully welded 1 mm thick AA5754 and AZ31 alloy sheets. Li et al. [ 18 ] successfully spot welded AZ31 magnesium alloy sheets to 1 mm thick 22MnB5 high-strength steel. Alaeibehmand et al. [ 19 , 20 ] overlap welded DP600 high-strength steel and AA6061 aluminum alloy of 2 mm thickness directly or through intermediate layers of Zn foil, brass coating of steel. Zhang et al. [ 21 ] conducted experiments on overlap welding of 2 mm thick T2 copper strip to 1060 pure aluminum rod using the pinless friction stir spot welding (FSSW) process. A 0.5 mm deep scroll groove shoulder was first used by Tozaki et al. [ 22 ] for FSSW. The tool was used to weld 2 mm thick 6061-T4 aluminum alloy sheets. The experimental observations showed that the scroll tool had comparable or superior performance to the conventional probe tool. The scroll groove played a significant role in mixing the material, and the shoulder penetration depth was an important welding process parameter. The authors compared it with a flat shoulder. In the case of a flat shoulder, the mixing was localized near the upper surface of the top sheet, indicating the absence of a downward flow of material. In the case of a shoulder with a scroll groove, the mixing was more intense. Under the action of the scroll groove, the material softened by frictional heating first moved toward the center of the welded area, then the flow was directed downward. Subsequently, the plasticized material moved toward the outer circumference of the shoulder indentation. It was also found that the weld structure depends significantly on shoulder plunge depth. Zhang et al. [ 23 ] also used a pinless tool to weld thin sheets of 2024-T3 aluminum alloy with a thickness of 1.6 mm. Three types of shoulders were considered: an inner-concave-flute shoulder, a concentric-circles-flute shoulder, and a three-spiral-flute shoulder. The best mixing and tensile strength close to the base material were demonstrated by the joint obtained by FSW with a shoulder with spiral flutes. Unfortunately, the authors of [ 23 ] did not indicate the groove depth. Later, shoulders with a larger number of grooves and more complex geometry appeared. Ni et al. [ 24 ] performed butt FSW on 0.5 mm thick AA7075-T6 alloy sheets using a shoulder with three “helical grooves”. The FSW was performed at high rotation and welding speeds. The groove depth was not specified. Rohani Yazdi et al. [ 25 ] performed FSSW on 2 mm thick 6061-T6 aluminum alloy sheets. They compared the performance of two shoulders with different groove configurations. One was a Tozaki design with scroll grooves [ 22 ], and the other had five L-shaped grooves with a depth of 0.5 mm. Welds produced using the L-groove shoulder exhibited slightly higher average shear strength than those with the scroll grooves. The increase in strength resulted from both the increased stir zone and the stir intensity caused by the sharp-angled grooves. Bakavos et al. [ 26 ] used five designs of pinless tool for FSSW: (a) the featureless flat tool, (b) the short flute wiper tool, (c) the long flute wiper tool, (d) the fluted scroll tool, and (e) the proud wiper tool. The depth of the grooves in the tools (a-d) and the height of the ridges in the tool (e) were 0.2 mm. The authors concluded that the weld strength depends on the groove configuration and that welds produced using grooved and non-grooved tools can have similar strength values depending on the welding conditions. Liu et al. [ 27 ] used four kinds of pinless tools (the six-groove tool, the large-curvature tool, the small-obliquity tool and the through-groove tool) and 2A12-T4 aluminum alloy was selected as the object of study. It was found that the six-groove tool provided the better transfer of plasticized material. In the above-mentioned works, much attention was paid to the shoulder design, the number and distribution of grooves. However, the role of the groove depth has not been studied at all. Meanwhile, the groove depth determines the volume of the displaced metal and the degree of its mixing, heat supply and, ultimately, determines the quality of the joint. It is obvious that a shoulder with scroll grooves is very effective for FSW of thin sheet metal. In the absence of a pin, the scroll grooves on the shoulder perform its role, improving mixing and facilitating the connection of workpieces. Since welding of thin sheets is an urgent task, it is of interest to study in more detail the operation of such a shoulder, optimize the depth of the scroll grooves and the welding pressure. The aim of this work was to investigate the effect of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution, material mixing, and formation of surface defects by mathematical modeling. Then, based on the modeling results, manufacture a shoulder with the optimal depth of the grooves and conduct an experiment to study the effect of pressure on the formation of a welded joint during butt welding of AA6063 aluminum alloy sheets. 2 Computer modeling methodology The temperature and mass transfer distribution during butt FSW were modeled using the CEL method, which is based on the combined use of Euler and Lagrange elements in the computer modeling process [ 28 , 29 ]. The idea behind the CEL approach is that the welded workpieces and the void represent Euler regions, and the tool is a Lagrangian body. This allows the Lagrangian body to penetrate into the workpiece at the tool-workpiece interface without distorting the mesh [ 30 ]. This modeling of the tool makes it possible to study the influence of the shoulder geometry and its interaction with the welded materials during FSW (Fig. 1 , a). On the surface of a shoulder with a diameter of 16 mm, two scroll grooves were modeled, shifted by 180 o relative to each other. The thickness of ridges between scroll grooves was 0.6 mm, and their pitch was 4 mm/revolution. During the modeling, the depth of the scroll grooves was varied from 0.0 to 0.5 mm with a pitch of 0.1 mm. AISI H13 steel was selected as the shoulder material (Fig. 1 b). In all calculation models, the data of the experiment [ 31 ] were used, where AA6063-T4 alloy sheets with a thickness of 3 mm were used as the material. The shoulder rotation speed was 1000 rpm, and the welding speed was 30 mm/min, the welding compression force was varied in the range of 1–3 kN. The welding pressure was calculated by dividing the welding force by the area of the flat shoulder. To capture the formation of burrs during welding, a void region (without any material assigned to it at the start of the simulation) was created above the Euler region of the workpiece. When the tool was plunged into the workpiece, the metal was extruded, forming burrs, and the void region captured this outgoing weld metal. Without the void region in the simulation, the burrs could not be analyzed and were lost in the environment. Since the Eulerian mesh is rigid, material velocity constraints were applied to both the bottom and side edges of the workpieces to prevent material escaping from the Eulerian volume. In the FSW simulation, the Eulerian workpieces were fixed in the x, y, and z directions, and rotational and translational boundary conditions were applied to the Lagrangian tool (Fig. 1 a). To meet the requirement for realistic simulation, convection and exchange heat transfer boundary conditions were considered. The natural convection between the workpiece/tool contact surface and the environment was defined by a convective heat transfer coefficient of 25 W/m 2 ×°C. The heat transfer between the base plate and the bottom surface of the workpiece was specified by a heat transfer coefficient of 4000 W/m 2 ×°C. At the beginning of the plunging stage, the temperature field around the workpieces was taken to be 25°C. The temperature distribution and material flow were modeled using the SIMULIA/Abaqus software package. Since the main factor in the formation of a joint during FSW is plastic flow, it was taken into account in computer modeling. In the mathematical model for modeling the plastic flow of a material, the Johnson-Cook plasticity equation [ 32 ] was used to simultaneously predict the plastic deformation of the material and the formation of defects: where m is the coefficient of thermal softening, \(\:\stackrel{-}{{\epsilon\:}}\:\) and are the effective plastic strain and strain rate, is the reference plastic strain rate, A is the initial yield strength of the material, B is the strain hardening coefficient, C is the strain rate sensitivity, n is the material hardening index during deformation, T r and T m are room temperature and melting temperature, respectively. The values of the parameters of the plasticity Eq. ( 1 ) are presented in Table 1 . Table 1 Values of the parameters of the Johnson-Cook plasticity model for the AA6063 alloy. Material А, MPa B, MPa С m n \(\:{\dot{}}_{0}\) Т r ( 0 С) Т m ( 0 С) AA6063 311 114 0.002 1.34 0.42 1 25 600 It is known that the thermal and mechanical properties of the material change nonlinearly with temperature. To simplify the calculations of the computer model, a number of values of the thermal properties of aluminum alloy and steel, independent of temperature, were used (Table 2 ). The coefficient of friction was chosen to be 0.4. Table 2 Thermophysical properties of the used materials. Thermophysical values AA6063 Steel - AISI H13 Density, ρ (kg/m 3 ) 2700 7850 Specific heat capacity, c (J/kg⋅K) 945 489 Specific heat of fusion, λ (kJ/kg) 390 210 Thermal conductivity, χ (W/m⋅K) 200 52 Coefficient of thermal expansion of metal, α ( \(\:\raisebox{1ex}{$1$}\!\left/\:\!\raisebox{-1ex}{${}^{0}С$}\right.\) ) 2.35×10 − 5 1.2×10 − 5 Modulus of elasticity, E (GPa) 70 210 Poisson’s ratio 0.33 0.3 For the flat aluminum alloy sheets, Euler elements of the EC3D8RT type (an 8-node thermally bonded element providing the benefits of reduced integration) were used (Fig. 2 ). For the mesh in the tool, the C3D4T element (a 4-node thermally bonded tetrahedron) was used. For the finite element mesh in the void region, EC3D8R elements were used. 3 Results of computer modeling and discussion Figure 3 Simulated distribution surface of the nodal temperature (NT11) of a welded joint of an aluminum alloy depending on the depth of the scroll grooves (1000 rpm, 30 mm/min, 5 MPa): a 0.5 mm; b 0.4 mm; c 0.3 mm; d 0.2 mm; e 0.1 mm; f 0 mm At groove depths of 0.5 and 0.4 mm (Fig. 3 a, b), a defect in the form of a space unfilled with material is observed near the lower surface of the sheet, as well as a large volume of burrs on the upper surface of the sheet. The greater the depth of the scroll grooves of the tool, the greater the volume of the discontinuity. The rupture of the sheet is caused by the movement of the welded metal by the scroll grooves and its displacement in the form of burrs. In this case, the area on the upper surface of the aluminum alloy heated to a high temperature is small, and the heating is observed mainly on the periphery of the shoulder. At a groove depth of 0.3 mm, there is no rupture of the lower surface of the sheet, and the area of the upper surface of the sheet heated to a high temperature is higher than at 0.4 mm. Heating is observed on the periphery of the shoulder (Fig. 3 c). The maximum heating of the surface of the welded sheets is observed at a groove depth of 0.2 mm (Fig. 3 d). In this case, the largest area of intense heating is formed, in which the maximum temperature of 435 o С is reached. With a shoulder with a groove depth of 0.1 mm and a flat shoulder (0 mm), the area of the heated material is insignificant (Fig. 3 e and f). In both cases, a narrow strip of material on the retreating side is heated most intensely. With a groove depth of 0.1 mm, a small heating area is observed in the center of the shoulder (Fig. 3 e). Figure 4 shows the result of modeling the effect of welding pressure on material mixing in the joint zone with a shoulder groove depth of 0.2 mm. Visualization of the flows and mixing of the welded materials is based on taking into account the output variable of the Eulerian material volume fraction (EVF). The output variable EVF measures the relative share of a specific portion of material in the Euler element. An EVF value of one (red scale color) indicates that the element is completely filled with the original portion of material. If the Euler volume fraction value is zero (blue scale color), then the original portion of material is completely outside the specified element. For elements in which the original portion of material is partially preserved, and the other part is filled with material from other cells of the same or neighboring workpiece, the program sets the color by interpolating the EVF values in neighboring elements. Since it is of interest to visualize primarily the mixing of material between the sheets rather than within each of them when welding the sheets, the EVF data output for the left (EVF_ASSEMBLY_AL1) and right (EVF_ASSEMBLY_AL2) sheets was performed separately to visualize the mixing area of the welded materials. In order to avoid overlapping of the sheet’s material, their images were manually shifted relative to each other. Thus, the gap size between the sheet images was proportional to the depth of interpenetration of the sheet materials. As the pressure increases, the depth of interpenetration of the sheet material increases (Fig. 4 ). At a pressure of 5 MPa, the width of the interpenetration zone is about 2 mm, and mixing is localized in the upper part of the joint. At 7.5 MPa, the width of the interpenetration zone of the material almost did not change, but the mixing depth towards the lower surface of the workpieces increased. At a pressure of 10 MPa, the width of the interpenetration zone was 3.8 mm. The mixing area reached the lower surface of the sheets, but the values of the EVF variable have an intermediate value, indicating that the original portions of the material were preserved in these cells. At 12.5 MPa, it is difficult to accurately determine the width of the interpenetration zone of the material, but it varies in the range of 3.5–5.3 mm. The mixing area reached the lower surface of the sheets, and the values of the EVF variable are zero, indicating that complete replacement of the original material in these cells occurred. At 15 MPa, mixing and interpenetration of the material of the sheets is most active, and the width of the interpenetration zone reaches about 8 mm. From the analysis of Fig. 4 it follows that with a scroll groove depth of 0.2 mm, complete joining of the alloy sheets is possible already at a pressure of 12.5 MPa. The obtained results can be explained if we take into account that the heating of the material during FSW occurs not only due to the friction forces on the contact surface of the tool with the material, but also due to the heat from the plastic deformation of the material volume. Recht proposed a mathematical model describing the temperature T in an infinitely thin shear band [ 34 , 35 ]. It was found that for a shear band, the temperature explicitly depends on the magnitude of the local strain \(\:\gamma\:\) and the strain rate \(\:\dot{\gamma\:}\) in accordance with the equation: $$\:T=\frac{{\tau\:}_{y}}{J}{\left[\frac{\dot{\gamma\:}(\gamma\:-{\gamma\:}_{y})}{\pi\:K\rho\:C}\right]}^{1/2}$$ 2 , where \(\:{\tau\:}_{y}\:\) and \(\:{\gamma\:}_{y\:}\:\) are the flow stress and shear strain, respectively; \(\:J\) is the mechanical equivalent of heat; \(\:K\) is the specific thermal conductivity; ρ is the density; \(\:C\) is the specific heat capacity; \(\:\gamma\:\) and \(\:\dot{\gamma\:}\:\) are the shear strain and strain rate in the shear plane, respectively. During FSW, high strains are achieved at high strain rates, so heat generation during deformation must be taken into account. Heat generation depending on the depth of the scroll grooves should be considered here. With a flat shoulder (0 mm) and a shoulder with a groove depth of 0.1 mm, the heat flow is insignificant, since it is generated mainly due to the friction force at the shoulder-workpiece interface. Since heat generation in friction pairs is directly proportional to the sliding velocity in all thermophysical friction models [ 36 ], maximum heating is observed at the periphery of the shoulder plunge area. In the case of deeper grooves, plastic deformation of the inner layers of the material is activated, due to which the heat of plastic deformation makes a significant contribution to the heating of the material. At 0.2 mm, the contribution from the heat of plastic deformation is maximum, and heat generation is observed over the entire surface of the shoulder-workpiece contact. At a groove depth of 0.4 and 0.5 mm, due to too strong mixing, a large volume of material is destroyed and carried to the surface in the form of a burr. In this case, a significant volume of material does not participate in the frictional and deformation heating of the material, and the temperature of the mixing zone decreases. 4 Verification of simulation results Based on the simulation results, a pinless shoulder with a diameter of 16 mm and two scroll grooves with a depth of 0.2 mm was made of AISI H13 steel with a hardness of 46 HRC. Sheets of AA6063-T4 aluminum alloy with a thickness of 3 mm were used for FSW. FSW mode: rotation speed − 1000 rpm, welding speed − 30 mm/min, shoulder pressure on the sample was varied in the range of 5–15 MPa. After FSW, the sheets were cut on an electrical discharge wire-cut machine perpendicular to the welding direction. Sections were prepared by polishing with diamond pastes of various powder granularities and a colloidal suspension based on silicon oxide. The macrostructure of the samples was examined using a Tescan Mira scanning electron microscope in the backscattered electron mode. Figure 5 shows macrosections of the joining area. It is evident that as the pressure increases, the thickness of the joint increases. Defect-free welding of two sheets occurred at a pressure of 15 MPa. Figure 6 shows the dependence of the formed joint thickness and sheets thickness on the welding pressure. As the pressure increases, the formed joint thickness increases, and the thickness of the sheets decreases. After welding at 15 MPa, the joint zone reaches the lower surface of the sheets, and the thickness of the sheets is 2.75 mm. Thus, there is good agreement between the experimental and simulation results. According to the simulation data, at a scroll groove depth of 0.2 mm, the area of mutual mixing of the sheet material reaches the lower surface of the sheets at 12.5 MPa. In the experiment, the welded joint was completely formed at a pressure of 15 MPa. The presented results show the possibility of significant reduction of labor intensity of experimental works on improvement of FSW technology, in particular optimization of welding tool profile, due to use of computer modeling. Some deviation of results of full-scale experiment from those obtained during modeling may be connected with the following assumptions: 1) created computer CEL model allows to predict depth of mixing zone in samples with accuracy of up to 8%; 2) during modeling the friction coefficient was set constant and equal to 0.4; 3) to simplify calculations of computer model a number of values of thermophysical properties of aluminum alloy and steel, independent of temperature, were used. 5 Conclusions The simulation showed a significant effect of the depth of the scroll grooves on the surface of the welding tool shoulder on the temperature distribution and the formation of surface defects during FSW. The use of scroll grooves allows us to increase the intensity of mixing and the temperature of the mixed area. The effect of the groove depth on the magnitude and distribution of temperature can be explained by the simultaneous action of frictional heating and heating from plastic deformation of the material volume. At a groove depth of 0.5 and 0.4 mm, the material is heated weakly and only near the periphery of the shoulder. In this case, a rupture of the material occurs near the lower surface of the sheets, and a large volume of burrs is formed on the upper surface. At a groove depth of 0.3 mm, there is no rupture of the lower surface of the sheets, and the area of the upper surface of the sheets heated to a high temperature is higher than at 0.4 mm. Heating is observed mainly at the periphery of the shoulder. The strongest heating on the surface of the welded sheets is observed at a groove depth of 0.2 mm. In this case, the largest area of strong heating is formed, in which the maximum temperature of 435 o С is reached. Strong and uniform heating at a groove depth of 0.2 mm is achieved due to the summation of heat from frictional heating and heat from plastic deformation of the material volume. In the case of a shoulder with a groove depth of 0.1 mm and a flat shoulder (0 mm), the area of the heated material is insignificant. In both cases, a narrow strip of material on the retreating side is heated most strongly. At a groove depth of 0.1 mm, a small heating area is observed in the center of the shoulder. In the last two cases, heating occurs mainly due to frictional action. Computer simulation showed that as the welding pressure increases, the depth of interpenetration of the sheet material increases. At a pressure of 5 MPa, the width of the interpenetration zone is about 2 mm, and mixing is localized in the upper part of the joint. At 7.5 MPa, the width of the material interpenetration zone almost did not change, but the depth of mixing towards the lower surface of the sheets increased. At a pressure of 10 MPa, the width of the interpenetration zone was 3.8 mm. The mixing area reached the lower surface of the sheets, but the values of the EVF variable have an intermediate value, indicating that the original portions of the material were preserved in these cells. At 12.5 MPa, the width of the material interpenetration zone is in the range of 3.5–5.3 mm. The mixing area reached the lower surface of the sheets, and the values of the EVF variable are zero, indicating that complete replacement of the original material in these cells occurred. At 15 MPa, the mixing and mutual penetration of the sheet material is the strongest, and the width of the mutual penetration area reaches 8 mm. With a scroll groove depth of 0.2 mm, complete joining of the alloy sheets is possible already at a pressure of 12.5 MPa. The results of computer modeling were verified by a full-scale experiment, which showed a good correlation with the modeling results. With a groove depth of 0.2 mm, the butt joint of the AA6063 alloy sheets was completely formed during FSW under a pressure of 15 MPa. Declarations Acknowledgments The work was supported by the Ministry of Science and Higher Education of the Russian Federation according to the State Assignment of the IMSP RAS (124022900006-2). The work was performed using the facilities of the shared services center “Structural and Physical Mechanical Studies of Materials” at the Institute for Metals Superplasticity Problems of Russian Academy of Sciences. The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. The authors have no relevant financial or non-financial interests to disclose. All authors contributed to the study conception and design. All authors have read and approved the final version of the manuscript for publication. Author contribution : Radmir Adilbekovich Rzaev – methodology, formal analysis, visualization, writing- original draft Nafis Fanisovich Khayretdinov – methodology, data curation Dilara Byazitovna Kabirova – investigation, data curation Rustem Fauzievich Fazlyakhmetov – resources Marcel Fanirevich Imayev - project administration, conceptualization, validation, supervision, writing – review and edition Leonid Moiseevich Gurevich – methodology, software Data availability The data can be obtained from the authors upon the submission of a reasonable request. Informed consent Not relevant Institutional review board statement Not relevant. Conflict of interest The authors declare no competing interests. References Thomas W M, Nicholas E D, Needham J C, Murch M G, Temple-Smith P and Dawes C J (TWI), 'Improvements relating to friction welding'. European Patent Specification EP 0 615 480 B1. 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DOI: 10.1016/s1003-6326(10)60632-2 Forcellese F, Gabrielli F, Simoncini M (2012) Mechanical properties and microstructure of joints in AZ31 thin sheets obtained by friction stir welding using ‘‘pin’’ and ‘‘pinless’’ tool configurations. Materials and Design 34: 219–229. doi:10.1016/j.matdes.2011.08.001 Kim K H, Bang H S, Bang H S, Kaplan A F H (2017) Joint properties of ultra thin 430M2 ferritic stainless steel sheets by friction stir welding using pinless tool. J of Materials Processing Technology 243: 381–386. http://dx.doi.org/10.1016/j.jmatprotec.2016.12.018 Simoncini M, Forcellese A (2012) Effect of the welding parameters and tool configuration on micro- and macro-mechanical properties of similar and dissimilar FSWed joints in AA5754 and AZ31 thin sheets. Materials and Design 41: 50–60. http://dx.doi.org/10.1016/j.matdes.2012.04.057 Taotao Li, Xiaolong Xie, Jingfeng Xu, Ruifeng Li, Kai Qi, Xiaoqiang Zhang, Hangyu Yue, Yue Zhao, Lei Qiao (2023) Research on AZ31 Mg alloy/22MnB5 steel pinless friction stir spot welding process and interfacial temperature field simulation. J of Materials Research and Technology 26, (9-10): 3710-3725. https://doi.org/10.1016/j.jmrt.2023.08.169 Saleh Alaeibehmand, Seyyed Ehsan Mirsalehi, Eslam Ranjbarnodeh (2021) Pinless FSSW of DP600/Zn/AA6061 dissimilar joints. J of Materials Research and Technology 15: 996-1006. https://doi.org/10.1016/j.jmrt.2021.08.071 Saleh Alaeibehmand, Eslam Ranjbarnodeh, Seyyed Ehsan Mirsalehi (2021) Joining mechanism in pinless FSSW of aluminum-steel with or without Zn and brass interlayers. Materials Characterization 180(10): 111400. https://doi.org/10.1016/j.matchar.2021.111400 Jinchen Zhang, Qiang Liu, Yongde Huang (2024) Influence of heat input on pinless friction stir spot welding of aluminum‑copper dissimilar materials. Materials Characterization 218: 114456. https://doi.org/10.1016/j.matchar.2024.114456 Tozaki Y, Uematsu Y. K. Tokaji (2010) A newly developed tool without probe for friction stir spot welding and its performance. J Mater Process Technol 210(6-7): 844. doi:10.1016/j.jmatprotec.2010.01.015 Liguo Zhang, Shude Ji, Guohong Luan, Chunlin Dong and Li Fu (2011) Friction stir welding of Al alloy thin plate by rotational tool without pin. J Mater Sci.Technol 27(7): 647–652 Ni Y, Fu L, Chen H Y (2019) Effects of travel speed on mechanical properties of AA7075-T6 ultra-thin sheet joints fabricated by high rotational speed micro pinless friction stir welding. J of Materials Processing Tech 265: 63–70. https://doi.org/10.1016/j.jmatprotec.2018.10.006 Rohani Yazdi S, Beidokhti B, Haddad-Sabzevar M (2019) Pinless tool for FSSW of AA 6061-T6 aluminum alloy. J of Materials Processing Tech. 267: 44–51. https://doi.org/10.1016/j.jmatprotec.2018.12.005 Dimitrios Bakavos, Yingchun Chen, Laurent Babout, Phil Prangnell (2011) Material interactions in a novel pinless tool approach to friction stir spot welding thin aluminum sheet. Metallurgical and Materials Transactions A 42: 1266–1282. https://doi.org/10.1007/s11661-010-0514-x Zhenlei Liu, Hutao Cui, Shude Ji, Minqiang Xu, Xiangchen Meng (2016) Improving joint features and mechanical properties of pinless fiction stir welding of Alcald 2A12-T4 aluminum alloy. J of Materials Science and Technology 32(12): 1372-1377. http://dx.doi.org/10.1016/j.jmst.2016.07.003 Das D, Bag S, Pal S (2021) A finite element model for surface and volumetric defects in the FSW process using a coupled Eulerian– Lagrangian approach. Sci Technol Weld Join 26: 412–419. https://doi.org/10.1080/13621718.2021.1931760 Li K, Jarrar F, Sheikh-Ahmad J, Ozturk F (2017) Using coupled Eulerian Lagrangian formulation for accurate modeling of the friction stir welding process. Procedia Engineering 207: 574–579. https://doi.org/10.1016/j.proeng.2017.10.1023 Meyghani B, Awang M B, Emamian S S, Nor M.K.B.M, Pedapati S R (2017) A comparison of different finite element methods in the thermal analysis of friction stir welding (FSW). Metals 7(450): 1- 23. https://doi.org/10.3390/met7100450 Sugonyako I S, Kabirova D B, Khayretdinov N F, Fazlyakhmetov R F, Imayev M F (2023) Growth of Al 3 Ni particles during friction stir processing of AA6063+NiO composite. Letters on Materials 13(4s): 431-437. https://doi.org/10.22226/2410-3535-2023-4-431-437 El-Moayed M H, Shash A Y, Rabou M A, El-Sherbiny M D (2021) A coupled statistical and numerical analysis of the residual properties of AA6063 friction stir welds. J of Advanced Joining Processes 3: 100042. DOI: 10.1016/j.jajp.2021.100042 Shash AY, El-Moayed M H, Rabou M A, El-Sherbiny M D (2022) A coupled experimental and numerical analysis of AA6063 friction stir welding. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science: 1- 9. DOI:10.1177/09544062221085884 Recht R F (1963) J. Appl. Mech., Paper No. 63-WA-67, 11:1-5 Meyers M A, Murr L E (1981) Shock waves and high-strain-rate phenomena in metals concepts and applications. Plenum Press Amosov A P (2011) Elementary Thermophysical Models of Friction. Izvestiya of Samara Scientific Center of the Russian Academy of Sciences 13 (4-3): 656-662. Cite Share Download PDF Status: Published Journal Publication published 20 Sep, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 21 Jul, 2025 Reviewers agreed at journal 06 Jul, 2025 Reviewers invited by journal 06 Jul, 2025 Editor assigned by journal 25 Jun, 2025 First submitted to journal 20 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6927846","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":481326391,"identity":"6e457f24-e5be-4d17-b214-8aef028e7638","order_by":0,"name":"Radmir Adilbekovich Rzaev","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Radmir","middleName":"Adilbekovich","lastName":"Rzaev","suffix":""},{"id":481326392,"identity":"c04323c2-6668-42a0-9c05-3c276ad34134","order_by":1,"name":"Nafis Fanisovich Khayretdinov","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Nafis","middleName":"Fanisovich","lastName":"Khayretdinov","suffix":""},{"id":481326393,"identity":"2f7866c8-ce59-40cf-a235-ce3f72aca534","order_by":2,"name":"Dilara Byazitovna Kabirova","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Dilara","middleName":"Byazitovna","lastName":"Kabirova","suffix":""},{"id":481326394,"identity":"10cd2eea-486b-4550-b614-7f932776ba53","order_by":3,"name":"Rustem Fauzievich Fazlyakhmetov","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Rustem","middleName":"Fauzievich","lastName":"Fazlyakhmetov","suffix":""},{"id":481326395,"identity":"e71926ea-8ece-46fb-a6ce-55b9376779c7","order_by":4,"name":"Marcel Fanirevich Imayev","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAnUlEQVRIiWNgGAWjYNCCAhseUrUYpJGu5TAJinXbzz788MHgvIxu/9kDzJVtRGgxO5NuLDnD4DaP2Y28BMazRGk5kMbGzAPWwmPA2EiUlvPP2Jj/GJzjMTt/hlgtN4C2MBgc4DE7kEO0lmfMkj0GyWC/HGw4R5TD0hg//Kiwszc7f/bgw4YyIrQgAR6GA6RpAGkZBaNgFIyCUYAVAABqNTMrQuOO5AAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-9386-7313","institution":"FSBIS Institute of Superplasticity in Metals Problems RAS: FGBUN Institut problem sverhplasticnosti metallov Rossijskoj akademii nauk","correspondingAuthor":true,"prefix":"","firstName":"Marcel","middleName":"Fanirevich","lastName":"Imayev","suffix":""},{"id":481326396,"identity":"0345dafe-1f0a-4daf-8c6a-a8ba56438df4","order_by":5,"name":"Leonid Moiseevich Gurevich","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Leonid","middleName":"Moiseevich","lastName":"Gurevich","suffix":""}],"badges":[],"createdAt":"2025-06-19 06:06:02","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6927846/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6927846/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-025-16540-5","type":"published","date":"2025-09-20T15:57:29+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86487667,"identity":"9a2ad319-39b1-447b-929f-e4851f4703e2","added_by":"auto","created_at":"2025-07-11 08:31:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":185200,"visible":true,"origin":"","legend":"\u003cp\u003eAssembly of the CEL-based model: \u003cstrong\u003ea\u003c/strong\u003e location of the Euler regions of the workpieces, the Lagrangian body of the tool and the welding boundary conditions; \u003cstrong\u003eb\u003c/strong\u003e drawing of the shoulder\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/19dab53fd241e23e75c10abf.png"},{"id":86487668,"identity":"f5776e1a-7f7c-424d-b976-ef1a9d28d6ba","added_by":"auto","created_at":"2025-07-11 08:31:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":348396,"visible":true,"origin":"","legend":"\u003cp\u003eFinite element mesh for welded materials and welding tool\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/7e304d17ef37a128f00020eb.png"},{"id":86487669,"identity":"eba15149-96af-4735-befc-459aea6a1f85","added_by":"auto","created_at":"2025-07-11 08:31:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":529529,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated distribution surface of the nodal temperature (NT11) of a welded joint of an aluminum alloy depending on the depth of the scroll grooves (1000 rpm, 30 mm/min, 5 MPa): \u003cstrong\u003ea\u003c/strong\u003e0.5 mm; \u003cstrong\u003eb\u003c/strong\u003e 0.4 mm; \u003cstrong\u003ec\u003c/strong\u003e 0.3 mm; \u003cstrong\u003ed\u003c/strong\u003e 0.2 mm; \u003cstrong\u003ee\u003c/strong\u003e 0.1 mm; \u003cstrong\u003ef\u003c/strong\u003e 0 mm\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/e7906dbaf87ea7ead3c3efce.png"},{"id":86487670,"identity":"b3417bf4-58dc-4c95-9970-2cb7ceeaf3cf","added_by":"auto","created_at":"2025-07-11 08:31:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":421189,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of the material of the simulated microsection from the welding pressure at a scroll groove depth of 0.2 mm: \u003cstrong\u003ea\u003c/strong\u003e 5 MPa; \u003cstrong\u003eb\u003c/strong\u003e 7.5 MPa; \u003cstrong\u003ec\u003c/strong\u003e 10 MPa; \u003cstrong\u003ed\u003c/strong\u003e 12.5 MPa; \u003cstrong\u003ee\u003c/strong\u003e 15 MPa\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/32ee96659207f76e560790f9.png"},{"id":86489013,"identity":"642cbf6d-747c-4808-a713-a635c806f733","added_by":"auto","created_at":"2025-07-11 08:47:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":191441,"visible":true,"origin":"","legend":"\u003cp\u003eImage of the joining area of AA6063 alloy sheets after FSW at different pressures: \u003cstrong\u003ea\u003c/strong\u003e 5 MPa; \u003cstrong\u003eb\u003c/strong\u003e 7.5 MPa; \u003cstrong\u003ec\u003c/strong\u003e 10 MPa; \u003cstrong\u003ed\u003c/strong\u003e 12.5 MPa; \u003cstrong\u003ee\u003c/strong\u003e 15 MPa. Polished surface. The advancing side is on the right\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/4c1683f41543854e67a3239b.png"},{"id":86488585,"identity":"1b193324-5af6-461d-82b6-a6cf920a1c3c","added_by":"auto","created_at":"2025-07-11 08:39:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":58443,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of welding pressure during FSW on the formed joint thickness and AA6063 alloy sheets thickness\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/91280165112f8bcfa8473c5e.png"},{"id":91889867,"identity":"98ad8dfd-e422-434b-87e4-8b393fd07987","added_by":"auto","created_at":"2025-09-22 16:02:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2202453,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6927846/v1/b9e58f1f-cd29-4a00-b8c6-ed66ddf91b2d.pdf"}],"financialInterests":"","formattedTitle":"Influence of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution and material mixing during FSW of AA6063 aluminum alloy sheets","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eFriction stir welding (FSW) was invented and patented in 1991 by TWI [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] and has since been widely used in manufacturing. FSW has proven to be much more efficient and provide higher mechanical properties than previously used welding methods such as metal inert gas (MIG) welding [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], tungsten inert gas (TIG) welding [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], laser welding [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], and resistance welding [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The FSW tool consists of two parts \u0026ndash; a shoulder and a pin. According to various estimates, 75\u0026ndash;80% of the heat flow is generated at the shoulder-workpiece boundary, and the remaining 20\u0026ndash;25% is released at the pin-workpiece boundary [\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. When applied to aluminum alloys, FSW allows joining workpieces up to 76.2 mm thick [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The disadvantage of using a tool consisting of a shoulder and a pin for thin sheets is the presence of a depression from the pin at the end of the weld, the so-called weld keyhole, which worsens the mechanical properties. To eliminate this defect, flat shoulders without a pin were used in a number of studies. In this case, the heat flow during stirring was created only by the friction force at the shoulder-workpiece interface. Zhang et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] used a simple cylindrical shoulder with a diameter of 15 or 20 mm to weld sheets of technically pure aluminum with a thickness of 1.8 mm in a friction stir lap welding manner. The absence of the pin had little effect on the heating behavior and cross-sectional profile of the joint after welding. It was also shown that the forging effect can be enhanced by tilting the tool, which is necessary to enhance the contact between the top and bottom sheets. Forcellese et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] investigated the influence of FSW parameters, tool geometry and size on the macro - and micromechanical properties of joints in 1.5 mm thick AZ31 magnesium alloy sheets. Two tools with shoulder diameters of 8 and 19 mm were used, each manufactured in pin and pinless versions. It was found that the shoulder diameter plays an important role in pinless FSW: an increase in the shoulder diameter from 8 to 19 mm led to an increase in the strength and ductility of the welded joints. Kim et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] obtained satisfactory properties of a butt joint of 0.5 mm thick 430M2 ultra-thin ferritic stainless steel sheets after FSW using a pinless tool made of WC-Co carbide.\u003c/p\u003e\u003cp\u003eThe pinless flat shoulder has also been applied for FSW of dissimilar alloys. Thus, Simoncini et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] successfully welded 1 mm thick AA5754 and AZ31 alloy sheets. Li et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] successfully spot welded AZ31 magnesium alloy sheets to 1 mm thick 22MnB5 high-strength steel. Alaeibehmand et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] overlap welded DP600 high-strength steel and AA6061 aluminum alloy of 2 mm thickness directly or through intermediate layers of Zn foil, brass coating of steel. Zhang et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] conducted experiments on overlap welding of 2 mm thick T2 copper strip to 1060 pure aluminum rod using the pinless friction stir spot welding (FSSW) process.\u003c/p\u003e\u003cp\u003eA 0.5 mm deep scroll groove shoulder was first used by Tozaki et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] for FSSW. The tool was used to weld 2 mm thick 6061-T4 aluminum alloy sheets. The experimental observations showed that the scroll tool had comparable or superior performance to the conventional probe tool. The scroll groove played a significant role in mixing the material, and the shoulder penetration depth was an important welding process parameter. The authors compared it with a flat shoulder. In the case of a flat shoulder, the mixing was localized near the upper surface of the top sheet, indicating the absence of a downward flow of material. In the case of a shoulder with a scroll groove, the mixing was more intense. Under the action of the scroll groove, the material softened by frictional heating first moved toward the center of the welded area, then the flow was directed downward. Subsequently, the plasticized material moved toward the outer circumference of the shoulder indentation. It was also found that the weld structure depends significantly on shoulder plunge depth. Zhang et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] also used a pinless tool to weld thin sheets of 2024-T3 aluminum alloy with a thickness of 1.6 mm. Three types of shoulders were considered: an inner-concave-flute shoulder, a concentric-circles-flute shoulder, and a three-spiral-flute shoulder. The best mixing and tensile strength close to the base material were demonstrated by the joint obtained by FSW with a shoulder with spiral flutes. Unfortunately, the authors of [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] did not indicate the groove depth.\u003c/p\u003e\u003cp\u003eLater, shoulders with a larger number of grooves and more complex geometry appeared. Ni et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] performed butt FSW on 0.5 mm thick AA7075-T6 alloy sheets using a shoulder with three \u0026ldquo;helical grooves\u0026rdquo;. The FSW was performed at high rotation and welding speeds. The groove depth was not specified. Rohani Yazdi et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] performed FSSW on 2 mm thick 6061-T6 aluminum alloy sheets. They compared the performance of two shoulders with different groove configurations. One was a Tozaki design with scroll grooves [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], and the other had five L-shaped grooves with a depth of 0.5 mm. Welds produced using the L-groove shoulder exhibited slightly higher average shear strength than those with the scroll grooves. The increase in strength resulted from both the increased stir zone and the stir intensity caused by the sharp-angled grooves. Bakavos et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] used five designs of pinless tool for FSSW: (a) the featureless flat tool, (b) the short flute wiper tool, (c) the long flute wiper tool, (d) the fluted scroll tool, and (e) the proud wiper tool. The depth of the grooves in the tools (a-d) and the height of the ridges in the tool (e) were 0.2 mm. The authors concluded that the weld strength depends on the groove configuration and that welds produced using grooved and non-grooved tools can have similar strength values depending on the welding conditions. Liu et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] used four kinds of pinless tools (the six-groove tool, the large-curvature tool, the small-obliquity tool and the through-groove tool) and 2A12-T4 aluminum alloy was selected as the object of study. It was found that the six-groove tool provided the better transfer of plasticized material.\u003c/p\u003e\u003cp\u003eIn the above-mentioned works, much attention was paid to the shoulder design, the number and distribution of grooves. However, the role of the groove depth has not been studied at all. Meanwhile, the groove depth determines the volume of the displaced metal and the degree of its mixing, heat supply and, ultimately, determines the quality of the joint. It is obvious that a shoulder with scroll grooves is very effective for FSW of thin sheet metal. In the absence of a pin, the scroll grooves on the shoulder perform its role, improving mixing and facilitating the connection of workpieces. Since welding of thin sheets is an urgent task, it is of interest to study in more detail the operation of such a shoulder, optimize the depth of the scroll grooves and the welding pressure.\u003c/p\u003e\u003cp\u003eThe aim of this work was to investigate the effect of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution, material mixing, and formation of surface defects by mathematical modeling. Then, based on the modeling results, manufacture a shoulder with the optimal depth of the grooves and conduct an experiment to study the effect of pressure on the formation of a welded joint during butt welding of AA6063 aluminum alloy sheets.\u003c/p\u003e"},{"header":"2 Computer modeling methodology","content":"\u003cp\u003eThe temperature and mass transfer distribution during butt FSW were modeled using the CEL method, which is based on the combined use of Euler and Lagrange elements in the computer modeling process [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The idea behind the CEL approach is that the welded workpieces and the void represent Euler regions, and the tool is a Lagrangian body. This allows the Lagrangian body to penetrate into the workpiece at the tool-workpiece interface without distorting the mesh [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. This modeling of the tool makes it possible to study the influence of the shoulder geometry and its interaction with the welded materials during FSW (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, a).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOn the surface of a shoulder with a diameter of 16 mm, two scroll grooves were modeled, shifted by 180 \u003csup\u003eo\u003c/sup\u003e relative to each other. The thickness of ridges between scroll grooves was 0.6 mm, and their pitch was 4 mm/revolution. During the modeling, the depth of the scroll grooves was varied from 0.0 to 0.5 mm with a pitch of 0.1 mm. AISI H13 steel was selected as the shoulder material (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). In all calculation models, the data of the experiment [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] were used, where AA6063-T4 alloy sheets with a thickness of 3 mm were used as the material. The shoulder rotation speed was 1000 rpm, and the welding speed was 30 mm/min, the welding compression force was varied in the range of 1\u0026ndash;3 kN. The welding pressure was calculated by dividing the welding force by the area of the flat shoulder.\u003c/p\u003e\u003cp\u003eTo capture the formation of burrs during welding, a void region (without any material assigned to it at the start of the simulation) was created above the Euler region of the workpiece. When the tool was plunged into the workpiece, the metal was extruded, forming burrs, and the void region captured this outgoing weld metal. Without the void region in the simulation, the burrs could not be analyzed and were lost in the environment.\u003c/p\u003e\u003cp\u003eSince the Eulerian mesh is rigid, material velocity constraints were applied to both the bottom and side edges of the workpieces to prevent material escaping from the Eulerian volume. In the FSW simulation, the Eulerian workpieces were fixed in the x, y, and z directions, and rotational and translational boundary conditions were applied to the Lagrangian tool (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). To meet the requirement for realistic simulation, convection and exchange heat transfer boundary conditions were considered. The natural convection between the workpiece/tool contact surface and the environment was defined by a convective heat transfer coefficient of 25 W/m\u003csup\u003e2\u003c/sup\u003e\u0026times;\u0026deg;C. The heat transfer between the base plate and the bottom surface of the workpiece was specified by a heat transfer coefficient of 4000 W/m\u003csup\u003e2\u003c/sup\u003e\u0026times;\u0026deg;C. At the beginning of the plunging stage, the temperature field around the workpieces was taken to be 25\u0026deg;C. The temperature distribution and material flow were modeled using the SIMULIA/Abaqus software package.\u003c/p\u003e\u003cp\u003eSince the main factor in the formation of a joint during FSW is plastic flow, it was taken into account in computer modeling. In the mathematical model for modeling the plastic flow of a material, the Johnson-Cook plasticity equation [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] was used to simultaneously predict the plastic deformation of the material and the formation of defects:\u003c/p\u003e\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"512\" height=\"45\"\u003e\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003em\u003c/em\u003e is the coefficient of thermal softening, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{{\\epsilon\\:}}\\:\\)\u003c/span\u003e\u003c/span\u003eand \u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAwAAAASCAYAAABvqT8MAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAACYSURBVDhPxZLrDUQREIXHlqAFxdAKnShBBfqgsFljZ3Kvx01W9sd+yYQTjmOEwgYc8OLxax4NWmtIKbG6OE447mEwKKV4tiLbfn8l51xPkgoh8ApDCYL3Ho0xrBBjjJTO6sOgcs5orWW1Z7Q3aq39VKqdeUmYrzAzNF1KgdYHqwfY2JmblES6prDk00vRJinSd/74vfcAvAHSoQ89tf4XAQAAAABJRU5ErkJggg==\" width=\"12\" height=\"18\"\u003eare the effective plastic strain and strain rate, \u003cimg src=\"data:image/png;base64,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\" width=\"16\" height=\"20\"\u003e is the reference plastic strain rate, \u003cem\u003eA\u003c/em\u003e is the initial yield strength of the material, \u003cem\u003eB\u003c/em\u003e is the strain hardening coefficient, \u003cem\u003eC\u003c/em\u003e is the strain rate sensitivity, \u003cem\u003en\u003c/em\u003e is the material hardening index during deformation, \u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003er\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e are room temperature and melting temperature, respectively. The values of the parameters of the plasticity Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eValues of the parameters of the Johnson-Cook plasticity model for the AA6063 alloy.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMaterial\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eА, MPa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eB, MPa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eС\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003em\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\dot{}}_{0}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003e\u003cem\u003eТ\u003c/em\u003e\u003csub\u003e\u003cem\u003er\u003c/em\u003e\u003c/sub\u003e (\u003csup\u003e0\u003c/sup\u003eС)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003eТ\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (\u003csup\u003e0\u003c/sup\u003eС)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAA6063\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e311\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e114\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e600\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIt is known that the thermal and mechanical properties of the material change nonlinearly with temperature. To simplify the calculations of the computer model, a number of values of the thermal properties of aluminum alloy and steel, independent of temperature, were used (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The coefficient of friction was chosen to be 0.4.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThermophysical properties of the used materials.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThermophysical values\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAA6063\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSteel - AISI H13\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDensity, ρ (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2700\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7850\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecific heat capacity, c (J/kg\u0026sdot;K)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e945\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e489\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecific heat of fusion, λ (kJ/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e390\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThermal conductivity, χ (W/m\u0026sdot;K)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCoefficient of thermal expansion of metal,\u003c/p\u003e\u003cp\u003eα (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\raisebox{1ex}{$1$}\\!\\left/\\:\\!\\raisebox{-1ex}{${}^{0}С$}\\right.\\)\u003c/span\u003e\u003c/span\u003e )\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.35\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.2\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eModulus of elasticity, E (GPa)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePoisson\u0026rsquo;s ratio\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFor the flat aluminum alloy sheets, Euler elements of the EC3D8RT type (an 8-node thermally bonded element providing the benefits of reduced integration) were used (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). For the mesh in the tool, the C3D4T element (a 4-node thermally bonded tetrahedron) was used. For the finite element mesh in the void region, EC3D8R elements were used.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"3 Results of computer modeling and discussion","content":"\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e Simulated distribution surface of the nodal temperature (NT11) of a welded joint of an aluminum alloy depending on the depth of the scroll grooves (1000 rpm, 30 mm/min, 5 MPa): \u003cb\u003ea\u003c/b\u003e 0.5 mm; \u003cb\u003eb\u003c/b\u003e 0.4 mm; \u003cb\u003ec\u003c/b\u003e 0.3 mm; \u003cb\u003ed\u003c/b\u003e 0.2 mm; \u003cb\u003ee\u003c/b\u003e 0.1 mm; \u003cb\u003ef\u003c/b\u003e 0 mm\u003c/p\u003e\u003cp\u003eAt groove depths of 0.5 and 0.4 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, b), a defect in the form of a space unfilled with material is observed near the lower surface of the sheet, as well as a large volume of burrs on the upper surface of the sheet. The greater the depth of the scroll grooves of the tool, the greater the volume of the discontinuity. The rupture of the sheet is caused by the movement of the welded metal by the scroll grooves and its displacement in the form of burrs. In this case, the area on the upper surface of the aluminum alloy heated to a high temperature is small, and the heating is observed mainly on the periphery of the shoulder. At a groove depth of 0.3 mm, there is no rupture of the lower surface of the sheet, and the area of the upper surface of the sheet heated to a high temperature is higher than at 0.4 mm. Heating is observed on the periphery of the shoulder (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The maximum heating of the surface of the welded sheets is observed at a groove depth of 0.2 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). In this case, the largest area of intense heating is formed, in which the maximum temperature of 435 \u003csup\u003eo\u003c/sup\u003eС is reached. With a shoulder with a groove depth of 0.1 mm and a flat shoulder (0 mm), the area of the heated material is insignificant (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee and f). In both cases, a narrow strip of material on the retreating side is heated most intensely. With a groove depth of 0.1 mm, a small heating area is observed in the center of the shoulder (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee).\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the result of modeling the effect of welding pressure on material mixing in the joint zone with a shoulder groove depth of 0.2 mm. Visualization of the flows and mixing of the welded materials is based on taking into account the output variable of the Eulerian material volume fraction (EVF). The output variable EVF measures the relative share of a specific portion of material in the Euler element. An EVF value of one (red scale color) indicates that the element is completely filled with the original portion of material. If the Euler volume fraction value is zero (blue scale color), then the original portion of material is completely outside the specified element. For elements in which the original portion of material is partially preserved, and the other part is filled with material from other cells of the same or neighboring workpiece, the program sets the color by interpolating the EVF values in neighboring elements.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSince it is of interest to visualize primarily the mixing of material between the sheets rather than within each of them when welding the sheets, the EVF data output for the left (EVF_ASSEMBLY_AL1) and right (EVF_ASSEMBLY_AL2) sheets was performed separately to visualize the mixing area of the welded materials. In order to avoid overlapping of the sheet\u0026rsquo;s material, their images were manually shifted relative to each other. Thus, the gap size between the sheet images was proportional to the depth of interpenetration of the sheet materials. As the pressure increases, the depth of interpenetration of the sheet material increases (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). At a pressure of 5 MPa, the width of the interpenetration zone is about 2 mm, and mixing is localized in the upper part of the joint. At 7.5 MPa, the width of the interpenetration zone of the material almost did not change, but the mixing depth towards the lower surface of the workpieces increased. At a pressure of 10 MPa, the width of the interpenetration zone was 3.8 mm. The mixing area reached the lower surface of the sheets, but the values of the EVF variable have an intermediate value, indicating that the original portions of the material were preserved in these cells. At 12.5 MPa, it is difficult to accurately determine the width of the interpenetration zone of the material, but it varies in the range of 3.5\u0026ndash;5.3 mm. The mixing area reached the lower surface of the sheets, and the values of the EVF variable are zero, indicating that complete replacement of the original material in these cells occurred. At 15 MPa, mixing and interpenetration of the material of the sheets is most active, and the width of the interpenetration zone reaches about 8 mm. From the analysis of Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e it follows that with a scroll groove depth of 0.2 mm, complete joining of the alloy sheets is possible already at a pressure of 12.5 MPa.\u003c/p\u003e\u003cp\u003eThe obtained results can be explained if we take into account that the heating of the material during FSW occurs not only due to the friction forces on the contact surface of the tool with the material, but also due to the heat from the plastic deformation of the material volume. Recht proposed a mathematical model describing the temperature \u003cem\u003eT\u003c/em\u003e in an infinitely thin shear band [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. It was found that for a shear band, the temperature explicitly depends on the magnitude of the local strain \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\gamma\\:\\)\u003c/span\u003e\u003c/span\u003e and the strain rate \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\dot{\\gamma\\:}\\)\u003c/span\u003e\u003c/span\u003e in accordance with the equation:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:T=\\frac{{\\tau\\:}_{y}}{J}{\\left[\\frac{\\dot{\\gamma\\:}(\\gamma\\:-{\\gamma\\:}_{y})}{\\pi\\:K\\rho\\:C}\\right]}^{1/2}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e\u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{y}\\:\\)\u003c/span\u003e\u003c/span\u003eand \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\gamma\\:}_{y\\:}\\:\\)\u003c/span\u003e\u003c/span\u003eare the flow stress and shear strain, respectively; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:J\\)\u003c/span\u003e\u003c/span\u003e is the mechanical equivalent of heat; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:K\\)\u003c/span\u003e\u003c/span\u003e is the specific thermal conductivity; ρ is the density; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:C\\)\u003c/span\u003e\u003c/span\u003e is the specific heat capacity; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\gamma\\:\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\dot{\\gamma\\:}\\:\\)\u003c/span\u003e\u003c/span\u003eare the shear strain and strain rate in the shear plane, respectively. During FSW, high strains are achieved at high strain rates, so heat generation during deformation must be taken into account. Heat generation depending on the depth of the scroll grooves should be considered here. With a flat shoulder (0 mm) and a shoulder with a groove depth of 0.1 mm, the heat flow is insignificant, since it is generated mainly due to the friction force at the shoulder-workpiece interface. Since heat generation in friction pairs is directly proportional to the sliding velocity in all thermophysical friction models [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], maximum heating is observed at the periphery of the shoulder plunge area. In the case of deeper grooves, plastic deformation of the inner layers of the material is activated, due to which the heat of plastic deformation makes a significant contribution to the heating of the material. At 0.2 mm, the contribution from the heat of plastic deformation is maximum, and heat generation is observed over the entire surface of the shoulder-workpiece contact. At a groove depth of 0.4 and 0.5 mm, due to too strong mixing, a large volume of material is destroyed and carried to the surface in the form of a burr. In this case, a significant volume of material does not participate in the frictional and deformation heating of the material, and the temperature of the mixing zone decreases.\u003c/p\u003e"},{"header":"4 Verification of simulation results","content":"\u003cp\u003eBased on the simulation results, a pinless shoulder with a diameter of 16 mm and two scroll grooves with a depth of 0.2 mm was made of AISI H13 steel with a hardness of 46 HRC. Sheets of AA6063-T4 aluminum alloy with a thickness of 3 mm were used for FSW. FSW mode: rotation speed \u0026minus;\u0026thinsp;1000 rpm, welding speed \u0026minus;\u0026thinsp;30 mm/min, shoulder pressure on the sample was varied in the range of 5\u0026ndash;15 MPa. After FSW, the sheets were cut on an electrical discharge wire-cut machine perpendicular to the welding direction. Sections were prepared by polishing with diamond pastes of various powder granularities and a colloidal suspension based on silicon oxide. The macrostructure of the samples was examined using a Tescan Mira scanning electron microscope in the backscattered electron mode.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;5 shows macrosections of the joining area. It is evident that as the pressure increases, the thickness of the joint increases. Defect-free welding of two sheets occurred at a pressure of 15 MPa.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the dependence of the formed joint thickness and sheets thickness on the welding pressure. As the pressure increases, the formed joint thickness increases, and the thickness of the sheets decreases. After welding at 15 MPa, the joint zone reaches the lower surface of the sheets, and the thickness of the sheets is 2.75 mm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThus, there is good agreement between the experimental and simulation results. According to the simulation data, at a scroll groove depth of 0.2 mm, the area of mutual mixing of the sheet material reaches the lower surface of the sheets at 12.5 MPa. In the experiment, the welded joint was completely formed at a pressure of 15 MPa.\u003c/p\u003e\u003cp\u003eThe presented results show the possibility of significant reduction of labor intensity of experimental works on improvement of FSW technology, in particular optimization of welding tool profile, due to use of computer modeling. Some deviation of results of full-scale experiment from those obtained during modeling may be connected with the following assumptions: 1) created computer CEL model allows to predict depth of mixing zone in samples with accuracy of up to 8%; 2) during modeling the friction coefficient was set constant and equal to 0.4; 3) to simplify calculations of computer model a number of values of thermophysical properties of aluminum alloy and steel, independent of temperature, were used.\u003c/p\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe simulation showed a significant effect of the depth of the scroll grooves on the surface of the welding tool shoulder on the temperature distribution and the formation of surface defects during FSW. The use of scroll grooves allows us to increase the intensity of mixing and the temperature of the mixed area. The effect of the groove depth on the magnitude and distribution of temperature can be explained by the simultaneous action of frictional heating and heating from plastic deformation of the material volume. At a groove depth of 0.5 and 0.4 mm, the material is heated weakly and only near the periphery of the shoulder. In this case, a rupture of the material occurs near the lower surface of the sheets, and a large volume of burrs is formed on the upper surface. At a groove depth of 0.3 mm, there is no rupture of the lower surface of the sheets, and the area of the upper surface of the sheets heated to a high temperature is higher than at 0.4 mm. Heating is observed mainly at the periphery of the shoulder. The strongest heating on the surface of the welded sheets is observed at a groove depth of 0.2 mm. In this case, the largest area of strong heating is formed, in which the maximum temperature of 435 \u003csup\u003eo\u003c/sup\u003eС is reached. Strong and uniform heating at a groove depth of 0.2 mm is achieved due to the summation of heat from frictional heating and heat from plastic deformation of the material volume. In the case of a shoulder with a groove depth of 0.1 mm and a flat shoulder (0 mm), the area of the heated material is insignificant. In both cases, a narrow strip of material on the retreating side is heated most strongly. At a groove depth of 0.1 mm, a small heating area is observed in the center of the shoulder. In the last two cases, heating occurs mainly due to frictional action.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eComputer simulation showed that as the welding pressure increases, the depth of interpenetration of the sheet material increases. At a pressure of 5 MPa, the width of the interpenetration zone is about 2 mm, and mixing is localized in the upper part of the joint. At 7.5 MPa, the width of the material interpenetration zone almost did not change, but the depth of mixing towards the lower surface of the sheets increased. At a pressure of 10 MPa, the width of the interpenetration zone was 3.8 mm. The mixing area reached the lower surface of the sheets, but the values of the EVF variable have an intermediate value, indicating that the original portions of the material were preserved in these cells. At 12.5 MPa, the width of the material interpenetration zone is in the range of 3.5\u0026ndash;5.3 mm. The mixing area reached the lower surface of the sheets, and the values of the EVF variable are zero, indicating that complete replacement of the original material in these cells occurred. At 15 MPa, the mixing and mutual penetration of the sheet material is the strongest, and the width of the mutual penetration area reaches 8 mm. With a scroll groove depth of 0.2 mm, complete joining of the alloy sheets is possible already at a pressure of 12.5 MPa.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe results of computer modeling were verified by a full-scale experiment, which showed a good correlation with the modeling results. With a groove depth of 0.2 mm, the butt joint of the AA6063 alloy sheets was completely formed during FSW under a pressure of 15 MPa.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e The work was supported by the Ministry of Science and Higher Education of the Russian Federation according to the State Assignment of the IMSP RAS (124022900006-2). The work was performed using the facilities of the shared services center \u0026ldquo;Structural and Physical Mechanical Studies of Materials\u0026rdquo; at the Institute for Metals Superplasticity Problems of Russian Academy of Sciences.\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll authors have read and approved the final version of the manuscript for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRadmir Adilbekovich Rzaev \u0026ndash; methodology, formal analysis, visualization, writing- original draft\u003c/p\u003e\n\u003cp\u003eNafis Fanisovich Khayretdinov \u0026ndash; methodology, data curation\u003c/p\u003e\n\u003cp\u003eDilara Byazitovna Kabirova \u0026ndash; investigation, data curation\u003c/p\u003e\n\u003cp\u003eRustem Fauzievich Fazlyakhmetov \u0026ndash; resources\u003c/p\u003e\n\u003cp\u003eMarcel Fanirevich Imayev - project administration, conceptualization, validation, supervision, writing \u0026ndash; review and edition\u003c/p\u003e\n\u003cp\u003eLeonid Moiseevich Gurevich \u0026ndash; methodology, software\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e The data can be obtained from the authors upon the submission of a reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed consent\u003c/strong\u003e Not relevant\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInstitutional review board statement\u003c/strong\u003e Not relevant.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col start=\"1\" type=\"1\"\u003e\n\u003cli\u003eThomas W M, Nicholas E D, Needham J C, Murch M G, Temple-Smith P and Dawes C J (TWI), \u0026apos;Improvements relating to friction welding\u0026apos;. 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Letters on Materials 13(4s): 431-437. https://doi.org/10.22226/2410-3535-2023-4-431-437 \u003c/li\u003e\n\u003cli\u003eEl-Moayed M H, Shash A Y, Rabou M A, El-Sherbiny M D (2021) A coupled statistical and numerical analysis of the residual properties of AA6063 friction stir welds. J of Advanced Joining Processes 3: 100042. DOI: 10.1016/j.jajp.2021.100042 \u003c/li\u003e\n\u003cli\u003eShash AY, El-Moayed M H, Rabou M A, El-Sherbiny M D (2022) A coupled experimental and numerical analysis of AA6063 friction stir welding. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science: 1- 9. DOI:10.1177/09544062221085884 \u003c/li\u003e\n\u003cli\u003eRecht R F (1963) J. Appl. Mech., Paper No. 63-WA-67, 11:1-5\u003c/li\u003e\n\u003cli\u003eMeyers M A, Murr L E (1981) Shock waves and high-strain-rate phenomena in metals concepts and applications. Plenum Press\u003c/li\u003e\n\u003cli\u003eAmosov A P (2011) Elementary Thermophysical Models of Friction. Izvestiya of Samara Scientific Center of the Russian Academy of Sciences 13 (4-3): 656-662. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Pinless friction stir welding, mathematical modeling, shoulder geometry, aluminum alloy, welding pressure","lastPublishedDoi":"10.21203/rs.3.rs-6927846/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6927846/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe aim of the work was to investigate the effect of the scroll groove depth and welding pressure on the temperature distribution and material mixing in pinless friction stir butt welding of AA6063 aluminum alloy sheets using the method of mathematical modeling. The tool was a shoulder with two scroll grooves, the depth of which varied from 0 to 0.5 mm with a step of 0.1 mm. Modeling showed a significant effect of the groove depth on the temperature distribution and the formation of surface defects. The maximum temperature and the largest area of strong heating were observed at a groove depth of 0.2 mm, which ensured a complete connection of sheets at a welding pressure of 12.5 MPa. The effect of the groove depth on the magnitude and distribution of temperature was explained based on the concepts of the action of two material heating mechanisms: 1) frictional heating and 2) heating from plastic deformation of the material volume. Strong and uniform heating at a groove depth of 0.2 mm was achieved by summing the heat from frictional heating and heat from plastic deformation. A full-scale experiment using a shoulder with a scroll groove depth of 0.2 mm showed good agreement with the simulation results.\u003c/p\u003e","manuscriptTitle":"Influence of the depth of scroll grooves of the shoulder and welding pressure on temperature distribution and material mixing during FSW of AA6063 aluminum alloy sheets","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-11 08:31:21","doi":"10.21203/rs.3.rs-6927846/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2025-07-21T11:25:47+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-07-06T18:18:06+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-06T16:44:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-25T06:19:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2025-06-21T02:43:50+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"31016b29-6b2c-49d8-ab1f-4ff4efbf5fdd","owner":[],"postedDate":"July 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-22T16:01:09+00:00","versionOfRecord":{"articleIdentity":"rs-6927846","link":"https://doi.org/10.1007/s00170-025-16540-5","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2025-09-20 15:57:29","publishedOnDateReadable":"September 20th, 2025"},"versionCreatedAt":"2025-07-11 08:31:21","video":"","vorDoi":"10.1007/s00170-025-16540-5","vorDoiUrl":"https://doi.org/10.1007/s00170-025-16540-5","workflowStages":[]},"version":"v1","identity":"rs-6927846","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6927846","identity":"rs-6927846","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}