Development of Friction Stir Welding and Processing

Topic Information

Dear Colleagues,

Friction stir welding (FSW), a mature solid-state joining method, has become a revolutionary welding technique over the past two decades due to its energy efficiency, environmental friendliness and high-quality joints. FSW is highly efficient in the joining of Al alloys, Mg alloys, Ti alloys, polymers and other similar materials. Derived from FSW, friction stir processing (FSP) is a solid-state processing technique to fabricate and modify bulk materials, composites and surface coatings, with tailored microstructures and enhanced mechanical properties, via severe plastic deformation and low temperature. Recently, FSW and FSP techniques have gained considerable scientific and technological attention in several fields, including aerospace, railway, renewable energy and automobile. Therefore, we expect that these fields may significantly contribute to accelerating the research and development in the areas of FSW and FSP.

This topic focuses on new FSW/P technologies and basic investigations into the affecting factors and the underlying mechanisms for these technologies. The topics of interest for this Special Issue, in particular, include (but are not restricted to):

• Novel FSW technologies via assisted energy to improve quality and efficiency;
• Friction stir modifications of surfaces to generate functional surfaces for tribological, corrosion, and design properties;
• Fabrication of new multifunctional materials based on severe plastic deformation and low temperature;
• Joining of different material combinations and dissimilar materials with coatings to improve interfacial metallurgy and joining performance;
• Control strategies for inherent issues in FSW/P area;
• Additive manufacturing for adapted friction stir-based technologies;
• Any other aspects of novel FSW and FSP technologies.

Prof. Dr. Yongxian Huang
Prof. Dr. Li Zhou
Dr. Xiangchen Meng
Dr. Yuming Xie
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Coatings coatings	2.9	5.0	2011	14.5 Days	CHF 2600
Materials materials	3.1	5.8	2008	13.9 Days	CHF 2600
Metals metals	2.6	4.9	2011	17.8 Days	CHF 2600
Journal of Manufacturing and Materials Processing jmmp	3.3	5.1	2017	16.5 Days	CHF 1800
Machines machines	2.1	3.0	2013	15.5 Days	CHF 2400

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Published Papers (18 papers)

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12 pages, 41376 KiB  

Open AccessArticle

Study on the Optimization of the Tensile Properties of an Al-Li Alloy Friction Stir-Welding T-Joint

by Yu Qiu, Yuansong Zeng, Qiang Meng, Wei Guan, Jihong Dong, Huaxia Zhao, Lei Cui, Xuepiao Bai and Mingtao Wang

Metals 2024, 14(9), 1040; https://doi.org/10.3390/met14091040 - 13 Sep 2024

Viewed by 1039

Abstract

The softening of aluminum–lithium alloy welded joints generally leads to a reduction in mechanical properties. In this study, a piece of 2A97-T3 aluminum–lithium alloy with a thickness of 2.8 mm was selected as the test material, and the tool and process used for [...] Read more.

The softening of aluminum–lithium alloy welded joints generally leads to a reduction in mechanical properties. In this study, a piece of 2A97-T3 aluminum–lithium alloy with a thickness of 2.8 mm was selected as the test material, and the tool and process used for wire-filled stationary shoulder friction stir welding (SSFSW) were developed. By increasing the bearing area of the softening zone, an equal-strength T-joint was manufactured. Good weld formation was obtained when the rotation speed was set to 2000 rpm and the welding speed ranged from 100 to 120 mm/min. The thickness of the softening zone was controlled by adjusting the reserved gap between the shoulder and the workpiece. The softening mechanism of the weld joint was revealed. The softening was attributed to the coarsening of the main precipitated phases (T1 and θ′ phases) in the heat-affected zone (HAZ) and the dissolution of precipitated phases in the thermo-mechanically affected zone (TMAZ). Grain refinement in the nugget zone (NZ) led to a certain fine-grained strengthening effect, although the precipitated phase was almost completely dissolved. Due to the thermal effect of second-pass welding, the hardness value of the NZ and HAZ in the center of the skin further decreased, and the minimum hardness was approximately 70% that of the base material. Tensile testing results indicated that the softening effect was largely offset by the increased bearing area of the softening zone, resulting in the successful welding of high-strength Al-Li alloy T-joints with equal strength. The strength coefficient was found to be 0.977. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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13 pages, 1030 KiB  

Open AccessArticle

Experimental Methodology to Identify Optimal Friction Stir Welding Parameters Based on Temperature Measurement

by Moura Abboud, Laurent Dubourg, Guillaume Racineux and Olivier Kerbrat

J. Manuf. Mater. Process. 2024, 8(4), 137; https://doi.org/10.3390/jmmp8040137 - 27 Jun 2024

Cited by 1 | Viewed by 1723

Abstract

Friction stir welding (FSW) is a widely employed welding process, in which advancing and rotational speeds consitute critical parameters shaping the welding outcome and affecting the temperature evolution. This work develops an experimental methodology to identify optimal FSW parameters based on real-time temperature [...] Read more.

Friction stir welding (FSW) is a widely employed welding process, in which advancing and rotational speeds consitute critical parameters shaping the welding outcome and affecting the temperature evolution. This work develops an experimental methodology to identify optimal FSW parameters based on real-time temperature measurement via a thermocouple integrated within the tool. Different rotational and welding speeds were tested on AA5083-H111 and AA6082-T6. Our results underscore the importance of attaining a minimum temperature threshold, specifically 0.65 times the solidus temperature, to ensure high-quality welds are reached. The latter are defined by combining temperature measurements with joint quality information obtained from cross-sectional views. Our research contributes to advancing the efficiency and effectiveness of friction stir welding in industrial settings. Furthermore, our findings suggest broad implications for the manufacturing industry, offering practical insights for enhancing weld quality and process optimization. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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20 pages, 7771 KiB  

Open AccessArticle

Active Vibration Avoidance Method for Variable Speed Welding in Robotic Friction Stir Welding Based on Constant Heat Input

by Guanchen Zong, Cunfeng Kang and Shujun Chen

Materials 2024, 17(11), 2593; https://doi.org/10.3390/ma17112593 - 28 May 2024

Viewed by 894

Abstract

Robotic Friction Stir Welding (RFSW) technology integrates the advantages of friction stir welding and industrial robots, finding extensive applications and research in aerospace, shipbuilding, and new energy vehicles. However, the high-speed rotational process of friction stir welding combined with the low stiffness characteristics [...] Read more.

Robotic Friction Stir Welding (RFSW) technology integrates the advantages of friction stir welding and industrial robots, finding extensive applications and research in aerospace, shipbuilding, and new energy vehicles. However, the high-speed rotational process of friction stir welding combined with the low stiffness characteristics of serial industrial robots inevitably introduces vibrations during the welding process. This paper investigates the vibration patterns and impacts during the RFSW process and proposes an active vibration avoidance control method for variable speed welding based on constant heat input. This method utilizes a vibration feedback strategy that adjusts the spindle speed actively if the end-effector’s vibration exceeds a threshold, thereby avoiding the modal frequencies of the robot at its current pose. Concurrently, it calculates and adjusts the welding speed of the robot according to the thermal equilibrium equation to maintain constant heat input. A simplified dynamic model of the RFSW robot was established, and the feasibility of this method was validated through simulation experiments. This study fills the gap in vibration analysis of RFSW and provides new insights into control strategies and process optimization for robotic friction stir welding. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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20 pages, 14380 KiB  

Open AccessArticle

Effect of Welding Parameters on Al/Mg Dissimilar Friction Stir Lap Welding with and without Ultrasonic Vibration

by Junjie Zhao, Bo Zhao, Chuansong Wu and Najib Ahmad Muhammad

Materials 2024, 17(9), 2109; https://doi.org/10.3390/ma17092109 - 29 Apr 2024

Viewed by 1389

Abstract

The amount of heat input during welding impacts the weld’s thermal and mechanical behavior and the joint’s properties. The current study involved conducting AA 6061 and AZ31B Mg dissimilar welding, using friction stir lap welding (FSLW) and ultrasonic vibration-enhanced FSLW (UVeFSLW). The comparison [...] Read more.

The amount of heat input during welding impacts the weld’s thermal and mechanical behavior and the joint’s properties. The current study involved conducting AA 6061 and AZ31B Mg dissimilar welding, using friction stir lap welding (FSLW) and ultrasonic vibration-enhanced FSLW (UVeFSLW). The comparison and analysis of the welding load, the weld’s macro-microstructure, intermetallic compounds (IMCs), and joint properties were conducted by adjusting the process parameters. The study also examined the effect of ultrasonic vibration (UV) variations on welding heat input. The study demonstrated that it is possible to reduce the welding load by employing UV. Moreover, this impact becomes more pronounced as the welding heat input decreases. Additionally, the material flow in the weld, the width of the weld nugget zone, and the continuous IMC layer are significantly influenced by ultrasonic vibration, irrespective of the heat input during welding. However, the impact on large areas of irregular IMCs or eutectic structures is relatively small. Furthermore, achieving better joint properties becomes more feasible when a higher welding speed is employed for the Al alloy placed on top. Specifically, the impact of UV becomes more evident at higher welding speeds (≥220 mm/min). Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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10 pages, 4795 KiB  

Open AccessCommunication

Shoulder-Restricted Friction Deposition for Aluminum Alloy Coatings on Titanium Alloys

by Yuanhang Guo, Jihong Dong, Zongliang Lv, Yuming Xie, Yongxian Huang and Xiangchen Meng

Coatings 2024, 14(1), 130; https://doi.org/10.3390/coatings14010130 - 19 Jan 2024

Viewed by 1623

Abstract

In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to [...] Read more.

In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to roughen the titanium substrate, the process verification of Al deposition onto TC4 was realized. The material utilization was close to 100%, and a deposition layer with a thickness of 0.8 mm and a strong bonded interface was obtained. The peel strength of the triple-layer deposited joints was 121 MPa. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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13 pages, 32448 KiB  

Open AccessArticle

Microstructure and Mechanical Properties of Friction Stir Lap Welding Joint of Al/CU Dissimilar Metals

by Fan Jiang, Wenquan Wang, Xinge Zhang and Wenbiao Gong

Metals 2023, 13(12), 1969; https://doi.org/10.3390/met13121969 - 3 Dec 2023

Cited by 6 | Viewed by 2174

Abstract

In this paper, 5083 aluminum alloy and T2 copper were selected for the friction stir lap welding test. The effect of intermetallic compounds on the microstructure and properties of Al/Cu dissimilar metal lap joints was studied. The results showed that the circulating Al/Cu [...] Read more.

In this paper, 5083 aluminum alloy and T2 copper were selected for the friction stir lap welding test. The effect of intermetallic compounds on the microstructure and properties of Al/Cu dissimilar metal lap joints was studied. The results showed that the circulating Al/Cu composite structure was formed on the advancing side of the lap joint, and the Al/Cu staggered hook-like structure and copper-rich region were generated on the retreating side. There was no typical ‘onion ring’ structure in the joint. Element diffusion occurred at the interface of the joint, forming a thin and uniform interfacial layer of Al/Cu intermetallic compounds, thus achieving a well-metallurgical bond at the Al/Cu interface. There were the intermetallic compounds Al₂Cu and Al₄Cu₉, without AlCu, in the lap joint. In addition, dynamic recrystallization occurred in the nugget zone, and higher dislocation density and dislocation entanglement were generated, which enhanced the deformation resistance in the nugget zone and increased the joint strength. The tensile test showed that the ductile–brittle mixed fracture occurred in the heat-affected zone on the advancing side of the aluminum plate, and the fracture had necking. The failure load of the lap joint was 4350 ± 30 N, about 80% of the aluminum base metal. The elongation of the Al/Cu dissimilar lap joint tensile specimen was 2.5%. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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56 pages, 7906 KiB  

Open AccessReview

A Review of Optimization and Measurement Techniques of the Friction Stir Welding (FSW) Process

by D. A. P. Prabhakar, Akash Korgal, Arun Kumar Shettigar, Mervin A. Herbert, Manjunath Patel Gowdru Chandrashekharappa, Danil Yurievich Pimenov and Khaled Giasin

J. Manuf. Mater. Process. 2023, 7(5), 181; https://doi.org/10.3390/jmmp7050181 - 7 Oct 2023

Cited by 17 | Viewed by 5722

Abstract

This review reports on the influencing parameters on the joining parts quality of tools and techniques applied for conducting process analysis and optimizing the friction stir welding process (FSW). The important FSW parameters affecting the joint quality are the rotational speed, tilt angle, [...] Read more.

This review reports on the influencing parameters on the joining parts quality of tools and techniques applied for conducting process analysis and optimizing the friction stir welding process (FSW). The important FSW parameters affecting the joint quality are the rotational speed, tilt angle, traverse speed, axial force, and tool profile geometry. Data were collected corresponding to different processing materials and their process outcomes were analyzed using different experimental techniques. The optimization techniques were analyzed, highlighting their potential advantages and limitations. Process measurement techniques enable feedback collection during the process using sensors (force, torque, power, and temperature data) integrated with FSW machines. The use of signal processing coupled with artificial intelligence and machine learning algorithms produced better weld quality was discussed. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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29 pages, 7721 KiB  

Open AccessFeature PaperReview

Review on the Solid-State Welding of Steels: Diffusion Bonding and Friction Stir Welding Processes

by Mahmoud Khedr, Atef Hamada, Antti Järvenpää, Sally Elkatatny and Walaa Abd-Elaziem

Metals 2023, 13(1), 54; https://doi.org/10.3390/met13010054 - 25 Dec 2022

Cited by 24 | Viewed by 5973

Abstract

Solid-state welding (SSW) is a relatively new technique, and ongoing research is being performed to fulfill new design demands, deal with contemporary material advancements, and overcome welding defects associated with traditional welding techniques. This work provides an in-depth examination of the advancements in [...] Read more.

Solid-state welding (SSW) is a relatively new technique, and ongoing research is being performed to fulfill new design demands, deal with contemporary material advancements, and overcome welding defects associated with traditional welding techniques. This work provides an in-depth examination of the advancements in the solid-state welding of steels through diffusion bonding (DB) and friction stir welding (FSW). Considerable attention was given to DB of steel, which overcame the difficulties of segregation, cracking, and distortion stresses that are usually formed in liquid-phase welding techniques. The defects that affected DB included two types: two-dimensional defects of a metallic lattice, i.e., phases and grain boundaries, and three-dimensional defects, i.e., precipitation. FSW, on the other hand, was distinguishable by the use of relatively low heat input when compared to fusion welding processes such as tungsten inert gas (TIG), resulting in the formation of a limited heat-affected zone. Moreover, fine grain structures were formed in the FSW interface because of the stirring tool’s severe plastic deformation, which positively affected the strength, ductility, and toughness of the FSW joints. For instance, higher strength and ductility were reported in joints produced by FSW than in those produced by TIG. Nevertheless, the HAZ width of the specimens welded by FSW was approximately half the value of the HAZ width of the specimens welded by TIG. Some defects associated with FSW related to the diffusion of elements, such as C/Cr atoms, through the weld zone, which affected the local chemical composition due to the formation of rich/depleted regions of the diffused atoms. Moreover, the lack-of-fill defect may exist when inappropriate welding conditions are implemented. On the other hand, the stirring tool was subjected to extensive wear because of the high hardness values, which negatively affected the economical usage of the FSW process. A summary of the results is presented, along with recommendations for future studies aimed at addressing existing difficulties and advancing the solid-state technology for steel. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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15 pages, 8933 KiB  

Open AccessArticle

Effect of Temperature and Material Flow Gradients on Mechanical Performances of Friction Stir Welded AA6082-T6 Joints

by Xiaotian Ma, Shuangming Xu, Feifan Wang, Yaobang Zhao, Xiangchen Meng, Yuming Xie, Long Wan and Yongxian Huang

Materials 2022, 15(19), 6579; https://doi.org/10.3390/ma15196579 - 22 Sep 2022

Cited by 21 | Viewed by 2563

Abstract

The temperature and material flow gradients along the thick section of the weld seriously affect the welding efficiency of friction stir welding in medium-thick plates. Here, the effects of different gradients obtained by the two pins on the weld formation, microstructure, and mechanical [...] Read more.

The temperature and material flow gradients along the thick section of the weld seriously affect the welding efficiency of friction stir welding in medium-thick plates. Here, the effects of different gradients obtained by the two pins on the weld formation, microstructure, and mechanical properties were compared. The results indicated that the large-tip pin increases heat input and material flow at the bottom, reducing the gradient along the thickness. The large-tip pin increases the welding speed of defect-free joints from 100 mm/min to 500 mm/min compared to the small-tip pin. The ultimate tensile strength and elongation of the joint reached 247 MPa and 8.7%, equal to 80% and 65% of the base metal, respectively. Therefore, reducing the temperature and material flow gradients along the thickness by designing the pin structure is proved to be the key to improving the welding efficiency for thick plates. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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6 pages, 1632 KiB  

Open AccessCommunication

Deformation-Driven Processing of CNTs/PEEK Composites towards Wear and Tribology Applications

by Yan Cui, Chong Li, Zenglou Li, Xiaojie Yao, Wenbo Hao, Songling Xing, Yuming Xie, Xiangchen Meng, Long Wan and Yongxian Huang

Coatings 2022, 12(7), 983; https://doi.org/10.3390/coatings12070983 - 12 Jul 2022

Cited by 7 | Viewed by 1861

Abstract

Despite wide applications in mechanical transmission components, sparked with extraordinary wear resistance, polymeric composites face the challenges of reinforcement agglomeration. In this work, deformation-driven processing was proposed to prepare carbon nanotube (CNTs)-reinforced poly-ether-ether-ketone (PEEK) matrix composites with enhancement in wear resistance. Severe plastic [...] Read more.

Despite wide applications in mechanical transmission components, sparked with extraordinary wear resistance, polymeric composites face the challenges of reinforcement agglomeration. In this work, deformation-driven processing was proposed to prepare carbon nanotube (CNTs)-reinforced poly-ether-ether-ketone (PEEK) matrix composites with enhancement in wear resistance. Severe plastic deformation contributed to the homogeneous dispersion of the reinforcements without undesirable agglomeration. Low frictional heat input ensured the structural integrity of CNTs. The coefficient of friction and wear rate of 3.0 wt.% CNTs/PEEK were, respectively, 7.32% and 6.71% lower than those of pure PEEK. This strategy provides a high-efficiency approach to preparing high wear-resistance polymeric composites, attributed to its self-heating, low-cost, and high-performance characteristics. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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26 pages, 16136 KiB  

Open AccessArticle

Immune Optimization of Double-Sided Welding Sequence for Medium-Small Assemblies in Ships Based on Inherent Strain Method

by Yi Shen, Suodong Liu, Mingxin Yuan, Xianling Dai and Jinchun Lan

Metals 2022, 12(7), 1091; https://doi.org/10.3390/met12071091 - 26 Jun 2022

Cited by 3 | Viewed by 1952

Abstract

The double-sided welding process is widely used in ship construction due to its high welding efficiency and forming quality. In order to further reduce the deformation caused by double-sided welding for medium-small assemblies in ships, the optimization of the double-sided welding sequence based [...] Read more.

The double-sided welding process is widely used in ship construction due to its high welding efficiency and forming quality. In order to further reduce the deformation caused by double-sided welding for medium-small assemblies in ships, the optimization of the double-sided welding sequence based on an artificial immune algorithm is carried out. First, the formation mechanism of welding deformation under the double-sided welding process is analyzed by the inherent strain method; next, the reduction of the welding deformation is taken as the optimization goal, and the welding sequence optimization model for double-sided welding is constructed; then, an immune clonal optimization algorithm based on similar antibody similarity screening and steady-state adjustment is introduced, and the immune optimization process for double-sided welding sequence is designed; finally, double-sided welding sequence optimization tests are carried out for four different types of medium-small assemblies in ships. Numerical test results show that, compared with IGA (Immune genetic algorithm), ICA (Immune clonal algorithm), and GA (Genetic algorithm), the maximum welding deformation caused by the welding sequence optimized by the proposed immune clonal algorithm is reduced by 2.4%, 2.8, and 3.3%, respectively, the average maximum welding deformation is reduced by 2.6%, 2.5, and 3.4%, respectively, and the convergence generation is reduced by 16.2%, 13.4, and 11.2%, respectively, which verifies the strong optimization ability and high optimization efficiency of the immune clonal algorithm introduced in the double-sided welding sequence optimization. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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18 pages, 8690 KiB  

Open AccessArticle

Influence of Plunge Depth on Temperatures and Material Flow Behavior in Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets: A Numerical Study

by Venkata Somi Reddy Janga and Mokhtar Awang

Metals 2022, 12(6), 927; https://doi.org/10.3390/met12060927 - 27 May 2022

Cited by 15 | Viewed by 2821

Abstract

Plunge depth is one of the most important process parameters that affect the joint strength in refill friction stir spot welding (refill FSSW). In this study, a three-dimensional numerical model is developed using the Lagrangian incremental formulation in DEFORM-3D to simulate the refill [...] Read more.

Plunge depth is one of the most important process parameters that affect the joint strength in refill friction stir spot welding (refill FSSW). In this study, a three-dimensional numerical model is developed using the Lagrangian incremental formulation in DEFORM-3D to simulate the refill FSSW process of thin AA7075-T6 sheets. The numerical model is verified by comparing the obtained temperatures at specific locations with the temperatures from the previous experimental studies. Material flow and temperature behaviors at three different plunge depths are analyzed using the numerical model. The temperatures and effective strains in the weld zone increased with an increase in plunge depth. The movement of the material in the stir zone is enhanced and a larger extent of material from the bottom sheet is involved in the stirring with the increase in plunge depth. The width and thickness of the stir zone are identified from the numerical model and are consistent with the experimental study from the literature. The increase and decrease in joint strength with the increase in plunge depth reported in the literature are correlated to the material flow behavior in the numerical models. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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16 pages, 8145 KiB  

Open AccessArticle

Restirring and Reheating Effects on Microstructural Evolution of Al–Zn–Mg–Cu Alloy during Underwater Friction Stir Additive Manufacturing

by Ying Li, Changshu He, Jingxun Wei, Zhiqiang Zhang, Ni Tian, Gaowu Qin and Xiang Zhao

Materials 2022, 15(11), 3804; https://doi.org/10.3390/ma15113804 - 26 May 2022

Cited by 11 | Viewed by 2329

Abstract

Friction stir additive manufacturing (FSAM) can be potentially used for fabricating high-performance components owing to its advantages of solid-state processing. However, the inhomogeneous microstructures and mechanical properties of the build attributed to the complex process involving restirring and reheating deserve attention. This study [...] Read more.

Friction stir additive manufacturing (FSAM) can be potentially used for fabricating high-performance components owing to its advantages of solid-state processing. However, the inhomogeneous microstructures and mechanical properties of the build attributed to the complex process involving restirring and reheating deserve attention. This study is based on the previous research of the underwater FSAMed 7A04 aluminum alloy and adopts a quasi in situ experimental method, i.e., after each pass of the underwater FSAM, samples were taken from the build for microstructural observation to investigate the restirring and reheating effects on microstructural evolution during the underwater FSAM. Fine-grain microstructures were formed in the stir zone during the single-pass underwater FSAM. After restirring, the grain size at the bottom of the overlapping region decreased from 1.97 to 0.87 μm, the recrystallization degree reduced from 74.0% to 29.8%, and the initial random texture transformed into a strong shear texture composed of the C {110}<$1\overline{1}0$>. After reheating, static recrystallization occurred in the regions close to the new additive zones, increasing the grain size and recrystallization degree. This study not only revealed the microstructural evolution during the underwater FSAM but also provided a guideline for further optimization of the mechanical properties of the Al–Zn–Mg–Cu alloy build. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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14 pages, 6126 KiB  

Open AccessArticle

The Influence of Tool Shape on Plastic Metal Flow, Microstructure and Properties of Friction Stir Welded 2024 Aluminum Alloy Joints

by Yumeng Sun, Wei Liu, Yupeng Li, Wenbiao Gong and Chuan Ju

Metals 2022, 12(3), 408; https://doi.org/10.3390/met12030408 - 26 Feb 2022

Cited by 13 | Viewed by 3118

Abstract

In this paper, the effect of different shapes of tool pin on the plastic flow of 2024-T6 aluminum alloy during friction stir welding was studied. In order to observe the plastic flow of materials more clearly, we chose the method of friction stir [...] Read more.

In this paper, the effect of different shapes of tool pin on the plastic flow of 2024-T6 aluminum alloy during friction stir welding was studied. In order to observe the plastic flow of materials more clearly, we chose the method of friction stir welding of dissimilar materials, considering the different corrosive characteristics of aluminum alloys made of different materials when exposed to the same corrosive liquid. By studying and comparing the temperature field, macro and microstructure, microhardness and tensile properties of welded joints, the results indicated that the metal in the weld nugget zone (WNZ) mainly came from the base metal of the advancing side, the thread being the driving force of the downward movement of the FSW plastic metal. The deep groove thread tool pin had the strongest ability to drive the metal downward. The conical cam thread tool pin had the strongest stirring effect on materials and the best metal fluidity. The macroscopic morphology, microstructure, mechanical properties and fracture morphology of different joints were analyzed, and the results showed that all joints could form an excellent union, with an onion ring pattern appearing in cross-section. The minimum grain size of the WNZ formed by the conical cam thread stirring head was 7~12 μm; the hardness was least at the junction of the heat affected zone (HAZ) and the thermo-mechanically affected zone (TMAZ). However, the hardness of the weld formed by the conical cam thread at this point was higher than that of other stirring heads; the tensile strength of all joints was more than 80% of the BM, and the maximum tensile strength of the joint welded by the conical cam thread tool pin was 364.27 MPa, accounting for 86.73% of the base metal (BM). The elongation after break was 14.95%. Tensile fracture morphology analysis showed that all joints were fractured by plastic fracture. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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19 pages, 84279 KiB  

Open AccessArticle

Comparison Study on Welding Temperature and Joint Characteristics of AZ31 Magnesium Alloy by Ultrasonic and Heat Pipe Assisted FSW

by Cheng-Gang Wei, Sheng Lu, Liang-Yu Chen and Mao-You Xu

Metals 2022, 12(2), 267; https://doi.org/10.3390/met12020267 - 31 Jan 2022

Cited by 6 | Viewed by 3120

Abstract

As an important factor in friction stir welding (FSW) process, temperature directly affects the microstructures and mechanical properties of welded joints. The present work aims to investigate the welding temperature and joint characteristics of AZ31 magnesium alloy under three FSW conditions: conventional friction [...] Read more.

As an important factor in friction stir welding (FSW) process, temperature directly affects the microstructures and mechanical properties of welded joints. The present work aims to investigate the welding temperature and joint characteristics of AZ31 magnesium alloy under three FSW conditions: conventional friction stir welding (FSW), ultrasonic assisted friction stir welding (UaFSW), and ultrasonic and heat pipe assisted friction stir welding (UHaFSW), respectively. The results show that the welding temperature distributions and the characteristic of “non-uniformity” are presented in the FSW and UaFSW joints along the welding and horizontal directions. Compared with conventional FSW, UaFSW can effectively balance and improve the non-uniform temperature distribution in the joints, resulting in the significant decreases in the peak temperatures and durations of high temperature. Hence, the grains are refined in the microstructure of the nugget zone in the UHaFSW joints, which enhances their microhardness and tensile properties. Based on these results, it can be concluded that UHaFSW could be an effective method to improve the mechanical properties of AZ31 magnesium alloy welded joints. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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16 pages, 12070 KiB  

Open AccessArticle

Microstructure and Mechanical Properties of Friction Stir-Welded Dissimilar Joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn Alloys

by Liangwen Xie, Xianyong Zhu, Yuexiang Fan, Weijia Sun, Peng Wang, Cheng Jiang, Xiong Xiao, Song Yang and Yulai Song

Materials 2022, 15(1), 23; https://doi.org/10.3390/ma15010023 - 21 Dec 2021

Cited by 7 | Viewed by 3373

Abstract

In order to clarify the microstructural evolution and the mechanical property of dissimilar friction stir-welded joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn magnesium alloys, two types of arrangement with ZK60 at advancing side (AS) or retreating side (RS) were adopted. The macrostructure and the microstructure [...] Read more.

In order to clarify the microstructural evolution and the mechanical property of dissimilar friction stir-welded joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn magnesium alloys, two types of arrangement with ZK60 at advancing side (AS) or retreating side (RS) were adopted. The macrostructure and the microstructure of the dissimilar welded joints were discussed, and the microhardness and the transverse tensile properties of the joints were measured. There are three stirring sub-zones with different compositions and two clear interfaces within the joints. Due to the effect of both the original grain size of base materials and the growth of recrystallized grains, in the stir zone (SZ), the grain size of ZK60 increased slightly, while the grain size of Mg-4.6Al-1.2Sn-0.7Zn decreased significantly. The dissolution of precipitates was gradually significant from RS to AS within the SZ due to the gradual increase in strain and heat. The grain refinement led to an increase in hardness, while the dissolution of precipitates resulted in a decrease in hardness. The performance of the joints obtained with ZK60 placed on the RS is slightly better than that of that on the AS. The tensile fracture of both joints occurred at the interface between SZ and the thermos-mechanical affected zone at the AS, and showed a quasi-dissociative fracture. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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17 pages, 8112 KiB  

Open AccessArticle

Fabrication and Characterization of Steel-Base Metal Matrix Composites Reinforced by Yttria Nanoparticles through Friction Stir Processing

by Essam R. I. Mahmoud, Hamad Almohamadi, Abdulrahman Aljabri, Sohaib Z. Khan, Ahmad N. Saquib, Mohammed Farhan and Mohammed Abdel-Ghani Elkotb

Materials 2021, 14(24), 7611; https://doi.org/10.3390/ma14247611 - 10 Dec 2021

Cited by 4 | Viewed by 2733

Abstract

Friction Stir Processing (FSP) was used to fabricate metal matrix composite, based on steel and reinforced with nano-sized yttrium oxide powder. The powder was packed in a narrow longitudinal groove of 2 mm depth and 1 mm width cut in the steel plate’s [...] Read more.

Friction Stir Processing (FSP) was used to fabricate metal matrix composite, based on steel and reinforced with nano-sized yttrium oxide powder. The powder was packed in a narrow longitudinal groove of 2 mm depth and 1 mm width cut in the steel plate’s rear surface. Different rotation speeds of 500–1500 rpm were used, at a fixed traveling speed of 50 mm·min⁻¹. Single-pass and two passes, with the same conditions, were applied. The direction of the second pass was opposite to that of the first pass. After the first pass, complete nugget zones were obtained when the rotation speeds were more than 700 rpm with some particles agglomeration. The added particles showed as narrow elliptical bands, with a band pitch equal to the rotation speed over traveling speed. Performing the second FSP pass in the opposite direction resulted in better particles distributions. Almost defect-free composite materials, with homogenously distributed yttria nano-sized particles, were obtained after two passes when rotation speeds more than 700 rpm were used. The resulting steel matrix grains were refined from ~60 μm of the base metal to less than 3 μm of the processed nugget zone matrix. The hardness and the tensile strength of the fabricated materials improved almost two-fold over the base metal. Uniform microhardness values within the nugget areas were observed at higher rotational speeds. The ductility and toughness of the fabricated composites were reduced compared to the base metal. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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20 pages, 5516 KiB  

Open AccessArticle

Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets

by Venkata Somi Reddy Janga, Mokhtar Awang, Mohd Fadillah Yamin, Uceu F. H. Suhuddin, Benjamin Klusemann and Jorge F. dos Santos

Materials 2021, 14(23), 7485; https://doi.org/10.3390/ma14237485 - 6 Dec 2021

Cited by 20 | Viewed by 3958

Abstract

The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of [...] Read more.

The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of AA7075-T6. The temperatures in the weld centre and outside the welding zone at selected points were recorded using K-type thermocouples for more accurate validation of the thermo-mechanical model. A thermo-mechanical three-dimensional refill FSSW model was built using DEFORM-3D. The temperature results from the refill FSSW numerical model are in good agreement with the experimental results. Three-dimensional material flow during plunging and refilling stages is analysed in detail and compared to experimental microstructure and hardness results. The simulation results obtained from the refill FSSW model correspond well with the experimental results. The developed 3D numerical model is able to predict the thermal cycles, material flow, strain, and strain rates which are key factors for the identification and characterization of zones as well for determining joint quality. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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