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1

Evaluation of friction stir welding on the microstructure and mechanical properties of dissimilar aluminum alloys 5083-O and 6061-T6 for automotive applications

Haryadi Gunawan Dwi, Taufik Muhammad Zaidan, Rochadian Okpina, Caesarendra Wahyu, Żak Krzysztof

Advances in Science and Technology. Research Journal

|

2025

|

Vol. 19, no. 9

34--49

EN

The Friction Stir Welding (FSW) process, employed for joining aluminium alloys, particularly the 5xxx and 6xxx series, is widely utilized in various applications, notably within the automotive industry. These alloy series exhibit properties that render them ideal for manufacturing components such as frames, chassis, and pistons due to their lightweight, strength, and corrosion resistance. FSW is especially advantageous as it presents an environmentally friendly alternative for aluminium welding, characterized by its low melting point, which facilitates precise thermal control during the welding process. This investigation focuses on the impact of FSW process parameters on the microstructure and mechanical properties of 5083-O and 6061-T6 aluminium alloys, Optimal welding conditions were determined to be a tool rotational speed of 1400 RPM, a travel speed of 30 mm/s, and a tool tilt angle of 1°. Under these parameters, a tensile strength efficiency of 75% relative to the 5083-O base material was achieved, with a maximum tensile strength recorded at 203.8449 MPa and a hardness range of 70.1-70.5 HV. Microstructural analysis reveals a clean weld surface devoid of significant defects that could compromise weld quality. The material exhibited equiaxed recrystallized grains in the WN zone under optimal parameters. Conversely, the most vulnerable aspect of the welded joint was consistently identified within the Heat Affected Zone (HAZ) of the 6061-T6 side across all parameter configurations. This susceptibility is attributed to grain growth and the dissolution of Mg2Si precipitates induced by the thermal effects during the FSW process, as corroborated by microphotographic analysis.

2

Information Retrieval in Friction Stir Welding of Aluminum Alloys by using Natural Language Processing based Algorithms

Mishra Akshansh

Welding Technology Review

|

2024

|

R. 96

147--154

EN

Text summarization is a technique for condensing a big piece of text into a few key elements that give a general impression of the content. When someone requires a quick and precise summary of a large amount of information, it becomes vital. If done manually, summarizing text can be costly and time-consuming. Natural Language Processing (NLP) is the sub-division of Artificial Intelligence that narrows down the gap between technology and human cognition by extracting the relevant information from the pile of data. In the present work, scientific information regarding the Friction Stir Welding of Aluminium alloys was collected from the abstract of scholarly research papers. For extracting the relevant information from these research abstracts four Natural Language Processing based algorithms i.e. Latent Semantic Analysis (LSA), Luhn Algorithm, Lex Rank Algorithm, and KL-Algorithm were used. In order to evaluate the accuracy score of these algorithms, Recall-Oriented Understudy for Gisting Evaluation (ROUGE) was used. The results showed that the Luhn Algorithm resulted in the highest f1-Score of 0.413 in comparison to other algorithms.

3

The effect of water cooling on the mechanical properties of FSW butt joints made of aluminium alloy AA7075-T651

Kosturek Robert, Śnieżek Lucjan, Torzewski Janusz

Materials Science and Welding Technologies / Technologie Materiałowe i Spawalnicze

|

2024

|

Vol. 68, No. 5

art. no. 4

EN

The article presents test results concerning the mechanical properties of friction stir welded joints (FSW) and underwater friction stir welded joints (UWFSW) made of aluminium alloy AA7075-T651. The analysis of microhardness distribution revealed two positive effects of water cooling, i.e. the reduction of the heat affected zone (HAZ) and an increase in the microhardness of the low hardness zone by approximately 15 HV0.1. Static tensile test results revealed that water cooling led to an increase in the yield point of the FSW joint by approximately 18 % (58 MPa) and tensile strength by approximately 9 % (43 MPa). Under low-cycle fatigue conditions, the UWFSW joints were characterised by higher stress amplitude, lower plastic strain amplitude and a lower number of cycles preceding the failure (of the UWFSW joints) than that preceding the failure of the “classical” FSW joints.

PL

W pracy przedstawiono wyniki badań właściwości mechanicznych połączeń FSW (Friction Stir Welding) oraz UWFSW Underwater Friction Stir Welding) stopu AA7075-T651. Analiza otrzymanych rozkładów mikrotwardości wykazała dwa pozytywne efekty chłodzenia wodnego, tj. zmniejszenie strefy wpływu ciepła oraz podwyższenie mikrotwardości strefy niskiej twardości o ok. 15 HV0.1. Wyniki statycznej próby rozciągania wskazują na wzrost granicy plastyczności połączenia FSW o ok. 18% (58 MPa) i wytrzymałości na rozciąganie o ok. 9% (43 MPa), na skutek zastosowania chłodzenia wodnego. W warunkach niskocyklowego zmęczenia połączenia UWFSW charakteryzują się wyższą amplitudą naprężenia, niższą amplitudą odkształcenia plastycznego i niższą liczbą cykli do zniszczenia niż połączenia FSW.

4

Multi-weld Quality Optimization of Friction Stir Welding for Aluminium Flange Using the Grey-based Taguchi Method

Sabry Ibrahim, ElWakil Mohamed, Hewidy A. M.

Management and Production Engineering Review

|

2024

|

Vol. 15, No. 2

42--56

EN

Friction stir welding (FSW) is gaining traction as a preferred technique due to its potential to reduce heat input and enhance the mechanical properties of welded joints. However, the path to commercializing FSW for flange joints is not without challenges. Two primary obstacles are the complexity of the welding path and the intricate design requirements for the fixtures. These factors contribute to the difficulty in determining the ideal weld settings and process parameters, which are critical for achieving optimal results. The current study addresses these challenges by applying FSW to flange joints using custom-engineered fixtures. These fixtures are meticulously designed to hold the pipes and plates securely during the welding process. The focus of the research is on optimizing the multi-performance characteristics of FSW for Al 6063 flange joints through the hybrid Grey-based Taguchi method. The integrity of the weld joint is assessed by examining various mechanical properties within the weld zone, including rotation speed, travel speed, tool profile, and shoulder diameter. The study identifies the optimal parameter settings for the FSW process: a rotation speed of 3000 rpm, a travel speed of 3 mm/min2, a shoulder diameter of 20 mm, and a conical tool profile. Under these ideal conditions, the welded material exhibited a tensile strength of 170.169 MPa, a hardness of 63.7709 HV, and a corrosion rate of 0.022 mm/year. These findings underscore the effectiveness of the optimized FSW process in producing robust and durable flange joints.

5

The effect of rotational speeds on the microstructural and mechanical properties of friction stir welded dissimilar aluminum alloy plates

Ngake Tankiso Lawrence, Mjali Kadephi Vuyolwethu

Engineering Transactions

|

2024

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Vol. 72, iss. 4

443--459

EN

The aim of this study is to investigate the effects of rotational speed on the quality of welds, microstructure, and mechanical properties in friction stir welding of dissimilar aluminum alloys (AA5083 and AA6082). Different samples were produced by varying the rotational speeds to 900, 1000, 1130, and 1260 rpm. The microstructure of the weld joints was evaluated by optical microscopy, while microhardness and tensile stress were examined using a microhardness tester and tensile tester. The microstructural analysis indicates fine equiaxed recrystallized grains in the stir zone for all the samples, regardless of rotational speeds. However, the macrographs indicated the development of voids with increasing rotational speeds. The lowest microhardness was observed in the stir zone for all the samples. The ultimate tensile stress decreased as rotational speed increased. Overall, the lowest rotational speed of 900 rpm yielded optimal results, with minimal defects and higher tensile strength.

6

Improving microstructural and mechanical properties of dissimilar friction stir welded AZ61/AZ40 joint

Wang Liang, Wang Jixiang, Cui Chengwu, Zhou Peishan, Wang Bin, Zheng Hualin

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 2

art. no. e66, 2024

EN

This study focuses on the microstructure evolution and mechanical properties of dissimilar magnesium alloy friction stir welded AZ61/AZ40 joints achieved at different traverse speeds (50-130 mm/min) and a constant rotation speed (1200 rpm). The surfaces of the welds are relatively smooth without any obvious surface defects except for the FSW joint at a traverse speed of 50 mm/min. The nugget zone (NZ) is bowl-shaped due to the tapered probe. The Mg-based alloys were sufficiently mixed with each other in the NZ, and the interface was irregular. In addition, the NZ exhibits fine equiaxed grains due to dynamic recrystallization (DRX), and the grain size decreases with increasing traverse speed. The welded joints show a relatively discontinuous microhardness, and the lowest microhardness occurs in the thermo-mechanically affected zone (TMAZ) on the advancing side (AS). The strength increases as the traverse speed increases from 50 to 70 mm/min and then decreases as the traverse speed increases continually. An exceptionally high tensile strength of 235 MPa was achieved at a traverse speed of 70 mm/min. The combined effects of high-density dislocations and fine second phases (η-Al8Mn5 and β-Mg17Al12 phase) promote mechanical properties.

7

Effect of heat input in dissimilar friction stir welding of A390-10 wt.% SiC composite–AA2024 aluminum alloy

Aval Hamed Jamshidi

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 3

art. no. e172, 2024

EN

This study investigates the impact of heat input, generated during friction stir welding, on the microstructure, mechanical properties, and corrosion resistance of dissimilar joints between A390-10 wt.% SiC composite and AA2024-T6 aluminum alloy. Welds were created using two rotational speeds: 600 rpm and 1600 rpm, while maintaining a constant traverse speed of 60 mm/min and employing a triangular pin tool. The results reveal that increasing the heat input from 125 to 354 J/mm leads to enhanced mixing in the stir zone, resulting in the formation of a layered structure. The stir zone area increases by 23% with the rise in heat input from 125 to 354 J/mm. Moreover, as the heat input and plastic strain in the stir zone increase, the particle size decreases by 31%, and their distribution becomes more uniform. Furthermore, an increase in heat input leads to the formation of coarser precipitates and particles on both the advancing and retreating sides, regardless of the type of precipitates formed. Conversely, reducing the heat input from 354 to 125 J/mm results in achieving maximum hardness (165.3 ± 2.3 HV0.1), yield strength (410.3 ± 11.3 MPa), ultimate tensile strength (514.5 ± 10.4 MPa), and minimum corrosion rate (0.41 mm/year).

8

Study on Underwater Friction Stir Welding of AA7075-T651

Kosturek Robert, Torzewski Janusz, Śnieżek Lucjan

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no. 8

191--203

EN

This study examines the application of additional water cooling on the mechanical properties of AA7075-T651 alloy friction stir welded butt joints. Underwater joints were produced in a wide range of welding parameters and compared to conventional FSW joints in terms of microhardness and basic mechanical properties. The low-cycle fatigue properties of selected FSW and UWFSW joints were also compared. It was stated that regardless of the welding parameters used, UWFSW joints outperform conventional FSW joints of the AA7075-T651 alloy in terms of YS and UTS, with only slightly lower ductility. The use of machining coolant enables the production of UWFSW joints with higher load-carrying capacity and greater ductility compared to FSW. Under low-cycle fatigue conditions, UWFSW joints exhibit a greater tendency for cyclic hardening, lower plastic strain amplitude, and fewer cycles to failure.

9

Structural integrity of AA7075-T651 UWFSW joints

Kosturek Robert, Ślęzak Tomasz, Torzewski Janusz

Advances in Materials Science

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2024

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Vol. 24, nr 4(82)

98--110

EN

This investigation is focused on the comparison of selected low-cycle fatigue properties of AA7075-T651 friction stir welded and underwater friction stir welded joints together with the evaluation of their lifetime prediction by the Manson-Coffin-Basquin formula. Additionally, the analysis of the fractured surface was involved to describe the character of joints decohesion. The analysis of the obtained hysteresis loops revealed that FSW joint exhibits cyclic hardening, with a stable maximum stress and a decreasing minimum stress, leading to an increased contribution of compressive stresses and a lower mean stress during stabilized fatigue. In comparison, the UWFSW joint also shows cyclic hardening but with a greater contribution of tensile stresses, a higher mean stress, and a reduced participation of plastic deformation. The Manson-Coffin-Basquin equation effectively predicts the fatigue life of AA7075-T651 alloy joints, with UWFSW joints showing significantly lower standard deviation (0.0035 vs. 0.0135) and narrower dispersion bands (1.61 vs. 1.93) compared to conventional FSW joints.

10

Deep Convolutional Neural Network Algorithm for Prediction of the Mechanical Properties of FSW Copper Welds from its Microstructure

Mishra Akshansh, Suman Asmita

Welding Technology Review

|

2023

|

R. 95

25--31

EN

Convolutional Neural Network (CNN) is a special type of Artificial Neural Network which takes input in the form of an image. Like Artificial Neural Network they consist of weights that are estimated during training, neurons (activation functions), and an objective (loss function). CNN is finding various applications in image recognition, semantic segmentation, object detection, and localization. The present work deals with the prediction of the welding efficiency of the Friction Stir Welded joints on the basis of microstructure images by carrying out training on 3000 microstructure images and further testing on 300 microstructure images. The loss function decreased for both training and testing set decreased with the increasing number of epochs. The obtained results showed an accuracy of 80 % on the validation dataset.

11

Numerical analysis of stress and temperature in the friction stir welding (FSW) process of steel

Szczecina Michał

Structure and Environment

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2023

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Vol. 15, no. 4

196--207

EN

Friction stir welding (FSW) is a modern technology for joining various metals, which has already undergone many laboratory tests, but still requires the development of numerical models. Author of the paper decided to summarize the current state of scientific knowledge regarding the modelling of the FSW process using the finite element method (FEM) and showed the main directions of development of numerical research on this process. Very advanced models are a combination of solid mechanics and fluid dynamics, but they often require expanding the computing environment with its own subroutines, as well as calibration and validation of some material parameter and constants occurring e.g. in the heat generation and heat flow laws. The Author of the paper proposed his own, simplified model, based on the computational solid mechanics and Lagrangian formulation. The model turned out to be an effective tool to reproduce stress and temperature fields during the FSW process.

PL

Zgrzewanie tarciowe z przemieszaniem (FSW) jest nowoczesną technologią łączenia różnych metali, posiadającą wiele zalet w porównaniu z tradycyjnym spawaniem. Zgrzewanie tarciowe zostało do tej pory poddane licznym badaniom laboratoryjnym, natomiast wymaga ciągłego rozwoju modeli numerycznych do symulacji tego procesu metodą elementów skończonych (MES). Autor artykułu postanowił dokonać podsumowania aktualnego stanu wiedzy dotyczącej modelowania zgrzewania tarciowego przy użyciu MES oraz wskazać główne kierunki rozwoju symulacji numerycznych tego procesu. Zaawansowane modele numeryczne zgrzewania tarciowego są kombinacją mechaniki ciała stałego z dynamiką płynów, a więc często wymagają rozbudowania środowiska obliczeniowego za pomocą własnych podprogramów, jak również kalibracji i walidacji wielu parametrów i stałych wymaganych do zdefiniowania np. prawa wytwarzania ciepła i prawa przepływu strumienia ciepła. Autor zaproponował swój własny uproszczony model bazujący na mechanice ciała stałego i opisie Lagrange’a. Model okazał się efektywnym narzędziem do odtworzenia naprężeń i pola temperatury w procesie zgrzewania tarciowego z przemieszaniem.

12

Wykonywanie połączeń różnoimiennych ze stopów aluminium metodami spawania łukowego i FSW

Węglowska Aleksandra, Rykała Janusz, Pfeifer Tomasz, Pietrzak Jacek

Maszyny Elektryczne : zeszyty problemowe

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2023

|

Nr 1 (128)

103--107

PL

Przedstawiono wyniki badań spawania TIG i MIG oraz zgrzewania FSW złączy z blach ze stopu aluminium EN AW6082, EN AW 5754 oraz odlewniczego stopu EN AC-43200. Scharakteryzowano stopy Al-Mg oraz Al-Mg-Si i ich spawalność. W ramach realizowanych badań przeprowadzono dobór warunków spawania i zgrzewania różnoimiennych stopów aluminium. Złącza poddano badaniom wizualnym, metalograficznym makroskopowym, penetracyjnym (złącza spawane) oraz własności mechanicznych w statycznej próbie rozciągania i zginania (złącza zgrzewane FSW). Na podstawie wyników badań realizowanych w Łukasiewicz – GIT oceniono, że jakość złączy spawanych zależy od przygotowania elementów do spawania, natomiast złączy zgrzewanych od parametrów zgrzewania i ustawienia stopów Al w złączu względem ruchu obrotowego narzędzia.

EN

Results of TIG, MIG and FSW welding technologies of joints made of EN AW-6082, EN AW 5754 aluminum alloy sheets and EN AC-43200 casting alloy are presented. This article briefly presents the characteristics of Al-Mg and Al-Mg-Si alloys and their weldability. As part of the research welding conditions for dissimilar aluminum alloys were selected. The joints were subjected to the visual and penetrant tests (TIG, MIG joints), light microscopy examination as well as tensile and bend tests (FSW joints). Based on the test results obtained in Łukasiewicz – GIT, it was found that the quality of arc welded joints depends on the preparation of the elements for welding, while the quality of FSW joints depends on the welding parameters and the positioning of Al alloys in the joint in relation to the rotational movement of the tool.

13

Research on the post-weld explosive hardening of AA7075-T651 friction stir welded butt joints

Kosturek Robert, Lewczuk Rafał, Torzewski Janusz, Wachowski Marcin, Słabik Piotr, Maranda Andrzej

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

|

Vol. 71, nr 4

art. no. e145685

EN

In this paper, the post-weld explosive hardening of a 5 mm AA7075-T651 plate welded via FSW was performed. To investigate the possibility of increasing FSW joint mechanical properties, the welded plate was explosively treated with four various explosive materials (ammonal, emulsion explosive, FOX-7, and PBX) in two different hardening systems. As part of the investigation, the observations of the surface and macrostructure of the treated plates were described. The obtained microhardness distribution allowed us to register the increase in hardness of the SZ up to 6%, but no increase in hardness of the LHZ was reported. In most cases, the influence of explosive treatment on the mechanical properties of the welded joint was disadvantageous as ultimate tensile strength and ductility were reduced. The only positive effect which was observed is the increase in the value of yield strength up to 27% corresponding to 77 MPa, achieved by explosive materials with detonation velocity below 3000 m/s.

14

The Effects of Friction Stir Welding Parameters on Microstructure, Fatigue Life and Tensile Properties of Aluminum 2024-T3 Alloy

Şık Aydın, Özer Alpay

Archives of Metallurgy and Materials

|

2023

|

Vol. 68, iss. 2

499--505

EN

In this study, Al 2024-T3 alloy plates were joined by using friction stir welding. Welding was performed at a rotational speed of 930, 1450, 2280 rpm and a welding feed rate of 180 mm min-1. The welded samples were analyzed at the microstructural level. Moreover, both bending fatigue tests and tensile tests were performed on samples. At the end of the microstructural examination of the samples welded at the rotational speed of 930 rpm and the welding feed rate of 180 mm min-1, the formation of tunnel defects was observed. The highest fatigue life was obtained at 2280 rpm and 180 mm min-1. The lowest fatigue life was obtained at 930 rpm and 180 mm min -1. The highest ultimate tensile stress was obtained at 2280 rpm/180 mm min-1 sample, which shows about a 12% reduction relative to the base material. The lowest ultimate tensile stress was obtained at 930 rpm/180 mm min-1 sample. The ultimate tensile stress value of the 930 rpm/180 mm min-1 sample decreased by approximately 25%.

15

Effect of Welding Conditions on Microstructural Evolution of Friction-Stir-Welded Ti-Cu Plate

Lee Yong-Jae, Jeong Won-Ki, Lee Seung-Jun, Fujii Hidetoshi, Shin Se Eun, Lee Dong-Geun

Archives of Metallurgy and Materials

|

2023

|

Vol. 68, iss. 1

131--135

EN

Fusion welding of Ti-Cu is difficult because of big difference of melting points and formation of brittle intermetallic compounds. Friction stir welding is carried out by solid-state joining, thermo-mechanical stirring, and friction heat. Ti-Cu FSW dissimilar welding can supply a very sound joint area with a few intermetallic compounds. Optimized welding process conditions are essential to obtain suitable microstructure and mechanical properties of welded zones. Different welding speeds affect the evolution of microstructure and mechanical properties due to changes of input heat and internal stored deformation energy. The correlation of microstructure and mechanical properties of Ti-Cu welded zone according to welding speeds were investigated and analyzed. As the higher the welding speed, the lower the heat input and the lower the temperature rise. Ti-Cu 75 has the smallest grain size at 13.9 μm, but the optimum mechanical properties and the integrity of welding were shown in Ti-Cu 50.

16

Influence of tool pin profile and welding parameters on microstructure and mechanical properties of dissimilar friction stir welded AA2024 to AA7075 alloys

Mohammed H. B., Naemah I. M., Jomah A. J. S., Alrubaiy A. A. A. G.

Archives of Materials Science and Engineering

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2023

|

Vol. 124, nr 1

14--24

EN

Purpose: The paper aims to produce aluminium welds in the solid state with good specifications and the least amount of welding defects by using the friction stir welding method (FSW) and different tool pin profiles and welding parameters. The research investigated the mechanical characteristics and microstructure of a friction stir welded dissimilar aluminium alloy (2024-T3 to 7075-0) through thickness produced by varying welding settings and three different FSW tool pin shapes. Design/methodology/approach: The objective is to obtain the welds with the least amount of welding defects in the solid state by using the friction stir welding method (FSW), designing the tool pin profiles, and changing the rotation speeds. Findings: According to tensile strength and micro-hardness tests, tool rotation of 2000 rpm and square pin profile were the best compared to other working parameters. The greatest hardness and highest tensile strength of FSWed dissimilar aluminium joints have been 144 HV and 215 MPa, respectively, when using the square pin profile at a tool rotation speed of 2000 rpm. The hardness and tensile strength of FSWed dissimilar aluminium alloy joints increase with the tool rotation speed. Microstructural observations of the FSWed dissimilar aluminium joints using a square pin profile at the tool rotation speed of 2000 rpm exhibited the weld zone's high weld quality. Additionally, there were no defects in the weld zone. The fracture surface of the FSWed joint indicated a ductile fracture type. Research limitations/implications: With many regions on either side of the weld with varied compositions, microstructures, and characteristics, the resulting welds of dissimilar alloys might result in unsatisfactory weld joints. Practical implications: The weld zone's exceptional weld quality was demonstrated by microstructural investigations of the FSWed dissimilar aluminium connections utilising a square pin profile at a tool rotation speed of 2000 rpm and feed rate of 20 mm per minute. Application in aerospace, shipbuilding and marine, railway, construction, electrical industries, and land transportation. Originality/value: The original value of the paper is the production of welds from dissimilar aluminium alloy (2024-T3 to 7075-0) with the least amount of welding defects by changing the tool pin profiles and tool rotation speeds using the friction stir welding method.

17

Computed Tomography and Scanning Electron Microscopy Analysis of a Friction Stir Welded Al-Cu Joint

Depczyński Wojciech P., Bańkowski Damian, Młynarczyk Piotr S.

Archives of Foundry Engineering

|

2023

|

Vol. 23, iss. 4

65--71

EN

The study aimed touse3D computed tomography (CT) to analyse a joint between two dissimilar materials produced by friction stir welding (FSW). As the materials joined, i.e., aluminum and copper, differ in properties (e.g., density and melting point), the weld is predicted to have an inhomogeneous microstructure. The investigations involved applying microfocus computed tomography (micro-CT) to visualize and analyze the volumetric structure of the joint. Volume rendering is extremely useful because, unlike computer modelling, which requires many simplifications, it helps create highly accurate representations of objects. Image segmentation into regions was performed through global gray-scale thresholding. The analysis also included elemental mapping of the weld cross-sections using scanning electron microscopy (SEM) and examination of its surface morphology by means of optical microscopy (OP). The joint finds its use in developing elements used in the chemical, energetics and aerospace industries, due to the excellent possibilities of combining many different properties, and above all, reducing the weight of the structure.

18

Mechanism of microstructure evolution and improved mechanical properties in two‑pass friction stir welding of titanium to aluminum

Kar Amlan

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 4

art. e231, 1--13

EN

This study investigates the impact of an additional pass on microstructure evolution, mechanical properties, and intermetallic compound formation during friction stir welding of aluminum and titanium. The microstructure analysis showed a complex mechanical mixing in the weld nugget that contained particles of varying sizes and the formation of intermetallic compounds. The formation of intermetallic compounds, such as Al3Ti and AlTi, was detected through chemical analyses and X-ray diffraction techniques. The microstructure of aluminum in the weld nugget comprised equi-axed grains with different grain boundaries and low orientation deviation. Such features in the evolution of the microstructure are attributed to continuous dynamic recrystallization due to its high stacking fault energy and favorable welding temperature and strain-induced dislocation activities. The presence of particles in aluminum and their homogeneous distribution after the second pass promote the state-IV hardening rate. A model for inhomogeneous materials was introduced to explain the variation in tensile properties with the number of passes, and the model correlated well with the cross-sectional microstructure analysis, which showed five distinct zones across the weld nugget. The study concludes that the improvement in mechanical properties after the second pass can be attributed to the development of interlayers, a defect-free interface, mechanical mixing, and continuous dynamic recrystallization of aluminum in the weld nugget.

19

Enhancing the properties of friction stir welded joints of L-PBF printed AlSi10Mg alloy via multi-variable optimization

Minhas Navdeep, Sharma Varun, Bhadauria Shailendra Singh

Archives of Civil and Mechanical Engineering

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2023

|

Vol. 23, no. 1

art. no. e60, 2023

EN

The feasibility study to join the laser powder bed fused AlSi10Mg alloy sheets using different friction stir welding parameters was investigated in the present work. Fifteen butt-welded joints using varied parametric combinations were developed based on the design of the experiment's approach. An empirical model between the process parameters and tensile strength was developed and used to understand the mechanical behavior of the welded joints w.r.t. the FSW parameters, followed by the attainment of optimized welding conditions using response surface methodology. The results inferred that the weldability was most significantly influenced by the tool rotational speed, followed by the tool tilt angle and tool traverse speed. The microstructure and mechanical properties of the optimized welded joint were compared with the as-built alloy and the welded joint yielding minimum tensile strength. The electron back scattered diffraction analysis revealed the reduction of average grain size of the stir zone of the joints by 21% for the optimized weld, as compared to the as-built alloy. The welded zones of the joints showed a reduction in hardness by 40-50% and formed the stir zone as the weakest link. The parametric combinations of the optimized weld improved the joint efficiency by ≈ 20% compared to the other weld, followed by an improvement in ductility, which was further characterized using scanning electron microscopy.

20

Enhancing heat and mass transfer to suppress void defects in friction stir welding by superimposing ultrasonic vibration

Wang Xue, Zhang Xiankun, Shi Lei, Wu Chuangsong, Chen Gaoqiang

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 4

art. e256, 1--16

EN

Heat and mass transfer in the process of friction stir welding (FSW) determine the weld formation quality. Meanwhile, the formation of voids in FSW limits welding speed improvement and welding efficiency. Although superimposing ultrasonic vibration can be adopted as an effective means to restrain the formation of voids, the potential suppression mechanism was still unrevealed. Herein, a multi-physical model using the shear stress boundary conditions was put forward to quantitatively study the influence of ultrasonic vibration on the heat and mass transfer behaviors and the resulting weld formation which was also validated experimentally. Our results show that ultrasonic vibration in FSW slightly enhances the heat flux at the tool-work piece interfacial contact surface as well as the plastic deformation heat generation near the tool. Therefore, the high-temperature area (higher than 690 K) near the tool pin side increases from 2.11 to 2.29 mm. The slightly higher heat rate and temperature enhance the fluidity of plastic material, resulting in an obvious increase in the flow velocity. As a consequence, the plastic material moves farther to fill the cavity at the rear advancing side, which is conducive to eliminating the void defects. The maximum strain rate on z = 2 mm horizontal plane at the AS is 206.7 s−1 in UVeFSW, while it is 13.5 s−1 in CFSW. The strain rate of the contact interface on AS increases by nearly 5 times, which implies an enhanced plastic material flow and is the main reason for suppressing void defects by superimposing ultrasonic vibration in FSW.