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Recent Achievements in Rotary, Linear and Friction Stir Welding of...
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Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 March 2018) | Viewed by 99655

Special Issue Editor

Prof. Dr. Giuseppe Casalino

E-Mail Website1 Website2
Guest Editor
Department of Mechanics Mathematics Management, Polytechnic University of Bari, 70125 Bari, Italy
Interests: advanced manufacturing; welding and joining; additive manufacturing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Rotary, linear, and friction stir welding of metals alloys are solid-state joining processes in which a joint between two metals can be formed by a combination of frictional heating and applied force.

While linear and rotary friction processes have been established as niche technologies in aero-engines and dissimilar metals circular parts, respectively, friction stir welding is fast becoming the process of choice for manufacturing lightweight transport structures.

As the interest of scientists and researchers have been growing exponentially, this Special Issue aims to collect recent meaningful researches that can help to significantly improve our understanding and the diffusion of those welding processes in the manufacturing practice of joining dissimilar and recent developed metal alloys.

The desired papers would report on the effect of frictional heating and applied force on metals microstructure and mechanical properties. Numerical and analytical models would explore the complexity of the thermal and mechanical phenomena interactions during the welding process. Quality solutions would warrant the reliability and reproducibility of the weld.

Therefore, contributions on weld characterization, quality solutions and process modeling of “Rotary, Linear and Friction Stir Welding” are encouraged and welcomed from academic and industrial experts and researchers.

Prof. Dr. Giuseppe Casalino
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • linear

  • rotary

  • stir friction welding

  • weld characterization

  • modeling

  • quality solutions

Published Papers (17 papers)

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Editorial

Jump to: Research, Review

2 pages, 160 KiB  
Editorial
Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys
by Giuseppe Casalino
Metals 2020, 10(1), 80; https://doi.org/10.3390/met10010080 - 02 Jan 2020
Cited by 7 | Viewed by 1640
Abstract
Rotary, linear, and friction stir welding of metal alloys are solid-state joining processes in which a joint between two metals can be formed by a combination of frictional heating and applied force [...] Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)

Research

Jump to: Editorial, Review

22 pages, 8703 KiB  
Article
Main Issues in Quality of Friction Stir Welding Joints of Aluminum Alloy and Steel Sheets
by Mian Wasif Safeen and Pasquale Russo Spena
Metals 2019, 9(5), 610; https://doi.org/10.3390/met9050610 - 25 May 2019
Cited by 46 | Viewed by 6482
Abstract
Joining of aluminum alloys through friction stir welding (FSW) is effectively employed in several industries (e.g., aeronautics and aerospace) since it guarantees proper weld strength as compared to other joining technologies. Contrarily, dissimilar FSW of aluminum alloys and steels often poses important issues [...] Read more.
Joining of aluminum alloys through friction stir welding (FSW) is effectively employed in several industries (e.g., aeronautics and aerospace) since it guarantees proper weld strength as compared to other joining technologies. Contrarily, dissimilar FSW of aluminum alloys and steels often poses important issues in the selection of welding parameters due to the difficulty to join different materials. Improper welding parameters give rise to the formation of intermetallic compounds, and internal and external defects (e.g., tunnel formation, voids, surface grooves, and flash). Intermetallic compounds are brittle precipitates of Al/Fe, which chiefly initiate crack nucleation, whereas internal and external defects mainly act as stress concentration factors. All these features significantly reduce joint strength under static and dynamic loading conditions. With reference to the literature, the influence of main welding parameters (rotational speed, welding speed, tool geometry, tilt angle, offset distance, and plunge depth) on the formation of intermetallic compounds and defects in FSW of aluminum alloys and steels is discussed here. Possible countermeasures to avoid or limit the above-mentioned issues are also summarily reported. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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20 pages, 3128 KiB  
Article
Thermomechanical Grain Refinement in AA6082-T6 Thin Plates under Bobbin Friction Stir Welding
by Abbas Tamadon, Dirk J. Pons, Kamil Sued and Don Clucas
Metals 2018, 8(6), 375; https://doi.org/10.3390/met8060375 - 23 May 2018
Cited by 33 | Viewed by 4148
Abstract
Bobbin friction stir welding (BFSW), with its fully penetrated pin and double-sided shoulder, can provide high rates of heat generation. This produces solid-state thermo-mechanical grain refinement. In this paper, the microstructure evolution of the welded joints of AA6082-T6 obtained using BFSW process was [...] Read more.
Bobbin friction stir welding (BFSW), with its fully penetrated pin and double-sided shoulder, can provide high rates of heat generation. This produces solid-state thermo-mechanical grain refinement. In this paper, the microstructure evolution of the welded joints of AA6082-T6 obtained using BFSW process was investigated with a focus on grain refinement. Two sheets of the AA6082-T6 alloy were butt-welded with a fixed-gap bobbin tool. The microstructure at a mid-weld transverse cross-section was evaluated using optical microscopy and electron backscatter diffraction (EBSD). Significant grain refinement was observed, with a decrease in grain size from 100 μm in directional columnar grain morphology of the base metal, to an ultrafine size—less than 10 μm—for the equiaxed grains in the stirring zone. The EBSD results showed that with BFSW processing, secondary phase precipitation patterns were produced that are distinct from the primary artificial age-hardening precipitates created by the T6 tempering cycle. The severe plastic deformation and heat generation appear to accelerate dynamic recrystallization and precipitation during the BFSW process. The microstructural studies confirmed that the BFSW process can provide a highly efficient thermodynamically activated grain refinement in the solid-state without requiring additional processes such as heat treatment or external means of grain refinement. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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15 pages, 30537 KiB  
Article
Effect of Cold Rolling on the Mechanical Properties and Formability of FSWed Sheets in AA5754-H114
by Giuseppe Casalino, Mohamad El Mehtedi, Archimede Forcellese and Michela Simoncini
Metals 2018, 8(4), 223; https://doi.org/10.3390/met8040223 - 28 Mar 2018
Cited by 15 | Viewed by 4494
Abstract
The effect of cold rolling, performed after friction stir welding (FSW), on the mechanical properties and formability of joints in AA5754-H114 aluminium alloy was investigated. Friction stir welding was carried out on 2.5 mm thick sheets with constant values of rotational and welding [...] Read more.
The effect of cold rolling, performed after friction stir welding (FSW), on the mechanical properties and formability of joints in AA5754-H114 aluminium alloy was investigated. Friction stir welding was carried out on 2.5 mm thick sheets with constant values of rotational and welding speeds of 1200 rpm and 100 mm/min, respectively. Then, FSWed workpieces were cold rolled, with the rolling direction perpendicular to the welding line, in order to obtain height reductions ranging from 0.1 to 0.5 mm. Cold rolling with the same height reductions was also carried out on the base material in the as-received condition. The mechanical properties and formability of both friction stir welded joints and base material, before and after cold rolling, were evaluated by means of the uniaxial tensile and hemispherical punch tests. The nominal stress vs. nominal strain and punch force vs. punch stroke curves were analysed in detail. Finally, the scanning electron microscope fractography was used to evaluate the fractured surface of tensile samples. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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17 pages, 71570 KiB  
Article
Friction Stir Welding of Non-Heat-Treatable High-Strength Alloy 5083-O
by Takashi Nakamura, Toshiyuki Obikawa, Itaru Nishizaki, Masatoshi Enomoto and Zhenglong Fang
Metals 2018, 8(4), 208; https://doi.org/10.3390/met8040208 - 23 Mar 2018
Cited by 24 | Viewed by 6332
Abstract
5083 aluminum alloy is increasingly used because of its excellent corrosion resistance, high work-hardening rate, and strength. In order to improve its weldability and feasibility, material behavior, material flow, and defects induced while friction stir welding 5083 should be studied. In this study, [...] Read more.
5083 aluminum alloy is increasingly used because of its excellent corrosion resistance, high work-hardening rate, and strength. In order to improve its weldability and feasibility, material behavior, material flow, and defects induced while friction stir welding 5083 should be studied. In this study, they were investigated by thermo-structural analysis. The flow stress of 5083-O has a high rate of sensitivity among high temperatures and wide strain rate ranges. Therefore, the details of the mechanical properties of 5083-O at high temperatures and wide strain rate ranges were investigated to obtain reasonable analysis results using a precise flow stress model. The tool/workpiece interface temperature during FSW is critical for accurate analysis results. This study used special equipment to measure tool temperature in order to investigate the interface temperatures precisely, and then the obtained data were used for optimization and verification of the thermal boundary conditions for analysis modeling. Using the developed model, the material behavior and material flow during FSW of 5083-O were analyzed. The tool and workpiece interface temperatures, flow stresses, strain rates, and velocities were investigated with the cylinder and threaded probes in detail. One of the analysis results indicated that the material flow rate on the rear side of a probe directly affected defect generation while joining. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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24 pages, 8135 KiB  
Article
Optimization of Friction Stir Weld Joint Quality Using a Meshfree Fully-Coupled Thermo-Mechanics Approach
by Kirk Fraser, Laszlo I. Kiss, Lyne St-Georges and Dany Drolet
Metals 2018, 8(2), 101; https://doi.org/10.3390/met8020101 - 31 Jan 2018
Cited by 35 | Viewed by 4468
Abstract
There is currently a need for an efficient numerical optimization strategy for the quality of friction stir welded (FSW) joints. However, due to the computational complexity of the multi-physics problem, process parameter optimization has been a goal that is out of reach of [...] Read more.
There is currently a need for an efficient numerical optimization strategy for the quality of friction stir welded (FSW) joints. However, due to the computational complexity of the multi-physics problem, process parameter optimization has been a goal that is out of reach of the current state-of-the-art simulation codes. In this work, we describe an advanced meshfree computational framework that can be used to determine numerically optimized process parameters while minimizing defects in the friction stir weld zone. The simulation code, SPHriction-3D, uses an innovative parallelization strategy on the graphics processing unit (GPU). This approach allows determination of optimal parameters faster than is possible with costly laboratory testing. The meshfree strategy is firstly outlined. Then, a novel metric is proposed that automatically evaluates the presence and severity of defects in the weld zone. Next, the code is validated against a set of experimental results for ½” AA6061-T6 butt joint FSW joints. Finally, the code is used to determine the optimal advancing speed and rpm while minimizing defect volume based on the proposed defect metric. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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22 pages, 7822 KiB  
Article
Formation Mechanisms for Entry and Exit Defects in Bobbin Friction Stir Welding
by Abbas Tamadon, Dirk J. Pons, Kamil Sued and Don Clucas
Metals 2018, 8(1), 33; https://doi.org/10.3390/met8010033 - 05 Jan 2018
Cited by 23 | Viewed by 5750
Abstract
Bobbin friction stir welding (BFSW) is an innovative variant for the solid state welding process whereby a rotating symmetrical tool causes a fully penetrated bond. Despite the process development, there are still unknown variables in the characterization of the process parameters which can [...] Read more.
Bobbin friction stir welding (BFSW) is an innovative variant for the solid state welding process whereby a rotating symmetrical tool causes a fully penetrated bond. Despite the process development, there are still unknown variables in the characterization of the process parameters which can cause uncontrolled weld defects. The entry zone and the exit zone consist of two discontinuity-defects and removing them is one of the current challenges for improving the weld quality. In the present research, the characteristic features of the entry and exit defects in the weld structure and formation mechanism of them during the BFSW processing was investigated. Using stacked layers of multi-colour plasticine the material flow, analogous to metal flow, can be visualised. By using different colours as the path markers of the analogue model, the streamline flow can be easily delineated in the discontinuity defects compared with the metal welds. AA6082-T6 aluminium plates and multi-layered plasticine slabs were employed to replicate the entry-exit defects in the metal weld and analogue samples. The fixed-bobbin tool utilized for this research was optimized by adding a thread feature and tri-flat geometry to the pin and closed-end spiral scrolls on both shoulder surfaces. Samples were processed at different rotating and longitudinal speeds to show the degree of dependency on the welding parameters for the defects. The analogue models showed that the entry zone and the exit zone of the BFSW are affected by the inhomogeneity of the material flow regime which causes the ejection or disruption of the plastic flow in the gap between the bobbin shoulders. The trial aluminium welds showed that the elimination of entry-exit defects in the weld body is not completely possible but the size of the defects can be minimized by modification of the welding parameters. For the entry zone, the flow pattern evolution suggested formation mechanisms for a sprayed tail, island zone and discontinuity-channel. For the exit zone a keyhole-shaped discontinuity is discussed as a structural defect. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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35921 KiB  
Article
Friction Stir Welding of near α and α + β Titanium Alloys: Metallurgical and Mechanical Characterization
by Kapil Gangwar, Ramulu Mamidala and Daniel G. Sanders
Metals 2017, 7(12), 565; https://doi.org/10.3390/met7120565 - 14 Dec 2017
Cited by 9 | Viewed by 4484
Abstract
Butt welds of friction stir welded dissimilar titanium alloys (near α: Ti-6242 standard grain (SG) and α + β ; Ti-54M) were produced for varying processing parameters (rotation speed: rpm and traverse speed; mm·min−1). Microstructures, microhardness, and fractured surfaces were analyzed [...] Read more.
Butt welds of friction stir welded dissimilar titanium alloys (near α: Ti-6242 standard grain (SG) and α + β ; Ti-54M) were produced for varying processing parameters (rotation speed: rpm and traverse speed; mm·min−1). Microstructures, microhardness, and fractured surfaces were analyzed for three different rpms and mm·min−1 with Ti-6242 SG and Ti-54M kept on the advancing and retreating side, respectively. While constant traverse speed (varying rotation speed) has no significant effect on micrographic patterns in weld nugget, constant rotation speed (with increasing traverse speed) results in an increasing number of streaks with specified spacing (advances per revolution) (consisting of material migrating from retreating side) on the advancing side. Although, hardness variation within streaks (due to lower values of v ω ; where v   and   ω are traverse and rotation speed) were challenging to evaluate, yet hardness maps imitated the micrographic morphology of the weld nugget. For varying rotation (225–325 rpm) and traverse speed (100–150 mm·min−1), corresponding microstructure evolutions on the advancing and retreating side were related, with variations in evolving temperatures for corresponding welding parameters. Fractured surfaces revealed an appearance of a combination of transcrystalline and intercrystalline fracture for all the processing parameters. Nature of solid state joining has been shown with a distinct boundary between Ti-6242 SG and Ti-54M, demonstrating the interlocking between streaks of different aspect ratios of these two alloys. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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7963 KiB  
Article
Microstructure and Mechanical Properties of Al/Steel Friction Stir Lap Weld
by Long Wan and Yongxian Huang
Metals 2017, 7(12), 542; https://doi.org/10.3390/met7120542 - 05 Dec 2017
Cited by 41 | Viewed by 6342
Abstract
The friction stir welding tool with convex pin tip was designed to realize the lap joining of 6082-T6 aluminum alloy and Q235A steel. With decreasing welding speed and increasing rotation speed, the basic constitutions of mixed stir zone changed from α-Fe fine grains, [...] Read more.
The friction stir welding tool with convex pin tip was designed to realize the lap joining of 6082-T6 aluminum alloy and Q235A steel. With decreasing welding speed and increasing rotation speed, the basic constitutions of mixed stir zone changed from α-Fe fine grains, thin intermetallic compound (IMC) and Al/Fe composite structure to hook-like and chaotic mixed layered structure, resulting in joint deterioration. The maximum shear load can reach 7500 N and is predominately affected by the morphology of the IMC layers, which in turn depend on rotation speed, welding speed and other parameters. Nano-hardness decreases from about 3.9 GPa in the upper steel surface layer to about 1.3 GPa in the steel base material. Microhardness profile reveals that the maximum hardness occurs at the interface zone. The morphology of layered structure, FeAl3 IMC thickness and steel grain size can be controlled by choosing suitable welding parameters and tool shape. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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Graphical abstract

4354 KiB  
Article
Experimental Validation of an FSW Model with an Enhanced Friction Law: Application to a Threaded Cylindrical Pin Tool
by Narges Dialami, Miguel Cervera, Michele Chiumenti, Antonio Segatori and Wojciech Osikowicz
Metals 2017, 7(11), 491; https://doi.org/10.3390/met7110491 - 10 Nov 2017
Cited by 15 | Viewed by 4194
Abstract
This work adopts a fast and accurate two-stage computational strategy for the analysis of FSW (Friction stir welding) processes using threaded cylindrical pin tools. The coupled thermo-mechanical problem is equipped with an enhanced friction model to include the effect of non-uniform pressure distribution [...] Read more.
This work adopts a fast and accurate two-stage computational strategy for the analysis of FSW (Friction stir welding) processes using threaded cylindrical pin tools. The coupled thermo-mechanical problem is equipped with an enhanced friction model to include the effect of non-uniform pressure distribution under the pin shoulder. The overall numerical strategy is successfully validated by the experimental measurements provided by the industrial partner (Sapa). The verification of the numerical model using the experimental evidence is not only accomplished in terms of temperature evolution but also in terms of torque, longitudinal, transversal and vertical forces. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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5814 KiB  
Article
3D Modelling of Flash Formation in Linear Friction Welded 30CrNiMo8 Steel Chain
by Pedro Effertz, Franz Fuchs and Norbert Enzinger
Metals 2017, 7(10), 449; https://doi.org/10.3390/met7100449 - 21 Oct 2017
Cited by 6 | Viewed by 4775
Abstract
Linear friction welding (LFW) is a solid-state welding process that has been thoroughly investigated for chain welding in recent years in order to replace the currently in use Flash Butt Welding (FBW) process. Modelling has proven to be an indispensable tool in LFW, [...] Read more.
Linear friction welding (LFW) is a solid-state welding process that has been thoroughly investigated for chain welding in recent years in order to replace the currently in use Flash Butt Welding (FBW) process. Modelling has proven to be an indispensable tool in LFW, thus providing necessary insight to the process, regardless of its final application. This article describes a 3D model developed in the commercial software DEFORM to study the LFW process of 30CrNiMo8 high strength steel in the Hero chain. Hence, a weakly coupled thermal and mechanical model were used, by means of the process experimental input such as displacement histories. The flash morphology and intervening mechanisms were analyzed. A thermal evaluation of different regions in the studied geometry was considered, and a correlation of the modeled and experimental width of the extrusion zone was established. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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0 pages, 8370 KiB  
Article
Development of Metallographic Etchants for the Microstructure Evolution of A6082-T6 BFSW Welds
by Abbas Tamadon, Dirk J. Pons, Kamil Sued and Don Clucas
Metals 2017, 7(10), 423; https://doi.org/10.3390/met7100423 - 11 Oct 2017
Cited by 30 | Viewed by 9914 | Correction
Abstract
BACKGROUND—The solid-phase joining of A6082-T6 plates by bobbin friction stir welding (BFSW) is problematic. Better methods are needed to evaluate the microstructural evolution of the weld. However, conventional Al reagents (e.g., Keller’s and Kroll’s) do not elucidate the microstructure satisfactorily, specifically regarding grain [...] Read more.
BACKGROUND—The solid-phase joining of A6082-T6 plates by bobbin friction stir welding (BFSW) is problematic. Better methods are needed to evaluate the microstructural evolution of the weld. However, conventional Al reagents (e.g., Keller’s and Kroll’s) do not elucidate the microstructure satisfactorily, specifically regarding grain size and morphology within the weld region. APPROACH—We developed innovative etchants for metallographic observations for optical microscopy. RESULTS—The macrostructure and microstructure of A6082-T6 BFSW welds were clearly demonstrated by optical microscopy analysis. The microetching results demonstrated different microstructures of the Stir Zone (S.Z) distinct from the Base Metal (B.M) and Heat Affected Zone (HAZ) & Thermo-mechanical Affected Zone (TMAZ). The micrographs showed a significant decrease in grain size from 100 μm in B.M to ultrafine 4–10 μm grains for the S.Z. Also, the grain morphology changed from directional columnar in the B.M to equiaxed in the S.Z. Furthermore, thermomechanical recrystallization was observed by the morphological flow of the grain distortion in HAZ and TMAZ. The etchants also clearly show the polycrystalline structure, microflow patterns, and the incoherent interface around inclusion defects. ORIGINALITY—Chemical compositions are identified for a suite of etchant reagents for metallographic examination of the friction-stir welded A6082-T6 alloy. The reagents have made it possible to reveal microstructures not previously evident with optical microscopy. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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9304 KiB  
Article
Study of the Microstructure Evolution and Properties Response of a Friction-Stir-Welded Copper-Chromium-Zirconium Alloy
by Ruilin Lai, Diqiu He, Guoai He, Junyuan Lin and Youqing Sun
Metals 2017, 7(9), 381; https://doi.org/10.3390/met7090381 - 19 Sep 2017
Cited by 16 | Viewed by 7879
Abstract
In this article, the copper-chromium-zirconium (CuCrZr) alloys plates with 21 mm in thickness were butt joined together by means of FSW (friction stir welding). The properties of the FSW joints are studied. The microstructure variations during the process of FSW were investigated by [...] Read more.
In this article, the copper-chromium-zirconium (CuCrZr) alloys plates with 21 mm in thickness were butt joined together by means of FSW (friction stir welding). The properties of the FSW joints are studied. The microstructure variations during the process of FSW were investigated by optical microscopy (OM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM). The results show that the grains size in the nugget zone (NZ) are significantly refined, which can be attributed to the dynamic recrystallization (DRX). The microstructure distribution in the NZ is inhomogeneous and the size of equiaxed grains are decreased gradually along the thickness direction from the top to bottom area of the welds. Meanwhile, it is found that the micro-hardness and tensile strength of the welds are slightly increased along the thickness direction from the top to the bottom area of the welds. All the nano-strengthening precipitates in the BM are dissolved into the Cu matrix in the NZ. Therefore, the decreases in hardness, tensile strength, and electrical conductivity can be attributed to the comprehensive effect of dissolution of nano-strengthening precipitates into the supersaturation matrix and severe DRX in the welded NZ. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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6608 KiB  
Article
Influence of Process Parameters on the Vertical Forces Generated during Friction Stir Welding of AA6082-T6 and on the Mechanical Properties of the Joints
by Archimede Forcellese, Michela Simoncini and Giuseppe Casalino
Metals 2017, 7(9), 350; https://doi.org/10.3390/met7090350 - 05 Sep 2017
Cited by 24 | Viewed by 5901
Abstract
The influence of the process parameters on the vertical force generated during friction stir welding of AA6082-T6 aluminium alloy sheet blanks was studied by performing experiments with constant values of the rotational speed, varying between 1200 and 2500 rpm, and welding speed, ranging [...] Read more.
The influence of the process parameters on the vertical force generated during friction stir welding of AA6082-T6 aluminium alloy sheet blanks was studied by performing experiments with constant values of the rotational speed, varying between 1200 and 2500 rpm, and welding speed, ranging between 30 and 100 mm/min. The effect of the tool dwelling was also analysed. The force vs. processing time curve has shown a very complex behaviour during the lowering motion of the pin tool related to the occurrence of both primary and secondary plunging. The tool dwelling produces a quick decrease in the vertical force with growing processing time until reaching a constant value. It was also seen that the tool dwelling does not influence the vertical force in the subsequent stage. As the tool began its welding motion, the vertical force immediately gets to a constant value until tool pulling out takes place. Furthermore, it was shown that the growth in the welding speed and the decrease in the rotational speed lead to an increase in the vertical force. The mechanical properties of the joints were evaluated versus the process parameters and the relationships among the ultimate tensile strength and ultimate elongation and the vertical force were defined. Finally, the microstructure developed during the friction stir welding was investigated and related to the mechanical properties of the joints. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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9183 KiB  
Article
A Finite Element Model to Simulate Defect Formation during Friction Stir Welding
by Zhi Zhu, Min Wang, Huijie Zhang, Xiao Zhang, Tao Yu and Zhenqiang Wu
Metals 2017, 7(7), 256; https://doi.org/10.3390/met7070256 - 07 Jul 2017
Cited by 58 | Viewed by 7973
Abstract
In this study, a 3D coupled thermo-mechanical finite element model is developed to predict and analyze the defect formation during friction stir welding based on coupled Eulerian Lagrangian method. The model is validated by comparing the estimated welding temperature, processed zone shape and [...] Read more.
In this study, a 3D coupled thermo-mechanical finite element model is developed to predict and analyze the defect formation during friction stir welding based on coupled Eulerian Lagrangian method. The model is validated by comparing the estimated welding temperature, processed zone shape and void size with those obtained experimentally. The results compared indicate that the simulated temperature and the data measured are in good agreement with each other. In addition, the model can predict the plasticized zone shape and the presence of a void in the weld quite accurately. However, the void size is overestimated. The effects of welding parameters and tool pin profile are also analyzed. The results reveal that welding at low welding speed or high tool rotational speed could produce a smaller void. Moreover, compared to a smooth tool pin, a featured tool pin can enhance plastic flow in the weld and achieve defect-free weldment. The results are helpful for the optimization of the welding process and the design of welding tools. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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9130 KiB  
Article
The Role of Mechanical Connection during Friction Stir Keyholeless Spot Welding Joints of Dissimilar Materials
by Xiao Liu, Xijing Wang, Boshi Wang, Liangliang Zhang, Chao Yang and Tingxi Chai
Metals 2017, 7(6), 217; https://doi.org/10.3390/met7060217 - 13 Jun 2017
Cited by 11 | Viewed by 4740
Abstract
Contrast experiments of lap joints among dissimilar AZ31B Mg alloy, Mg99.50, zinc-coated DP600 sheet, and non-zinc-coated DP600 sheet were made by friction stir keyholeless spot welding (FSKSW) and vacuum diffusion welding (VDW), respectively. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) were [...] Read more.
Contrast experiments of lap joints among dissimilar AZ31B Mg alloy, Mg99.50, zinc-coated DP600 sheet, and non-zinc-coated DP600 sheet were made by friction stir keyholeless spot welding (FSKSW) and vacuum diffusion welding (VDW), respectively. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) were used to investigate the microstructures and components of the joints welded. The experimental results show that the FSKSW bonding method is a kind of compound mode that contains a mechanical connection and element diffusion fusion connection, in which mechanical connection has the main decisive function on joints of Mg/steel. Elements diffusion exists in the interfacial region of the joints and the elements diffusion extent is basically the same to that of VDW. The elements’ diffusion in Mg/steel using FSKSW is defined in the reaction between small amounts elements of the base metal and zinc-coated metals. The intermetallic compounds and composite oxide perform some reinforcement on the mechanical connection strength. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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Review

Jump to: Editorial, Research

1343 KiB  
Review
A Comparison of Different Finite Element Methods in the Thermal Analysis of Friction Stir Welding (FSW)
by Bahman Meyghani, Mokhtar B. Awang, Seyed Sattar Emamian, Mohd Khalid B. Mohd Nor and Srinivasa Rao Pedapati
Metals 2017, 7(10), 450; https://doi.org/10.3390/met7100450 - 21 Oct 2017
Cited by 71 | Viewed by 9190
Abstract
Friction Stir Welding (FSW) is a novel kind of welding for joining metals that are impossible or difficult to weld by conventional methods. Three-dimensional nature of FSW makes the experimental investigation more complex. Moreover, experimental observations are often costly and time consuming, and [...] Read more.
Friction Stir Welding (FSW) is a novel kind of welding for joining metals that are impossible or difficult to weld by conventional methods. Three-dimensional nature of FSW makes the experimental investigation more complex. Moreover, experimental observations are often costly and time consuming, and usually there is an inaccuracy in measuring the data during experimental tests. Thus, Finite Element Methods (FEMs) has been employed to overcome the complexity, to increase the accuracy and also to reduce costs. It should be noted that, due to the presence of large deformations of the material during FSW, strong distortions of mesh might be happened in the numerical simulation. Therefore, one of the most significant considerations during the process simulation is the selection of the best numerical approach. It must be mentioned that; the numerical approach selection determines the relationship between the finite grid (mesh) and deforming continuum of computing zones. Also, numerical approach determines the ability of the model to overcome large distortions of mesh and provides an accurate resolution of boundaries and interfaces. There are different descriptions for the algorithms of continuum mechanics include Lagrangian and Eulerian. Moreover, by combining the above-mentioned methods, an Arbitrary Lagrangian–Eulerian (ALE) approach is proposed. In this paper, a comparison between different numerical approaches for thermal analysis of FSW at both local and global scales is reviewed and the applications of each method in the FSW process is discussed in detail. Observations showed that, Lagrangian method is usually used for modelling thermal behavior in the whole structure area, while Eulerian approach is seldom employed for modelling of the thermal behavior, and it is usually employed for modelling the material flow. Additionally, for modelling of the heat affected zone, ALE approach is found to be as an appropriate approach. Finally, several significant challenges and subjects remain to be addressed about FSW thermal analysis and opportunities for the future work are proposed. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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