Friction Stir Research Articles

Investigations on mechanical and surface properties of friction stir welded dissimilar joints of 2507 SDSS and 317L ASS

Friction stir welding (FSW), recognized as an eco-friendly and safe welding technique, finds widespread application across industries including aerospace, and automotive sectors. As a key material in production, stainless steel (SS) has great application potential in FSW. In this article, solid-state joining of dissimilar materials 2507 super duplex stainless steel (SDSS) and 317 L austenitic stainless steel (ASS), using FSW was investigated. By adjusting the position of 2507 SDSS and 317 L ASS, this paper examined the mechanical and surface properties of the joints at rotation speed of 400 rpm and welding speed of 20 mm/min. The results revealed that alteration of the material position seemed to have negligible influence on the joint's appearance, tensile behavior, and failure location. However, a clear grain refinement post-FSW in the joints was recorded, leading to a substantial increase in the hardness of the center stir zone (CSZ), alongside noticeably enhanced wear resistance. This grain refinement also contributed to an improvement in the corrosion resistance of the joints.

Study on microstructure and corrosion behavior of T-joints of 2A12 and 2A97 aluminum alloys by FSW

T-shaped joints of high-strength aluminum alloy welded by friction stir welding (FSW) are expected to replace the traditional riveting structures. However, the popularization of FSW in aerospace industry is still hindered the corrosion of T-joint. Herein, T-joints of 2A12 and 2A97 aluminum alloys are prepared and studied via structural characterization and corrosion tests. The microstructures and constituents of different micro zones in T-joints before and after corrosion tests are characterized and analyzed particularly. The internal relationship between different micro zones in T-joints and their corrosion behaviors are clarified, which provides theoretical basis for improving welding process and surface protection after welding.

Ultrasonic-induced amorphization and strengthening mechanisms of ultrasonic vibrations assisted friction stir Al/Ti welds

Integration of aluminum (Al) and titanium (Ti) alloys offers an effective approach to sustainable and high-quality development of the automotive and aviation industries. However, challenges arise when welding Al alloys to Ti alloys due to the formation of detrimental intermetallic compounds at the interface. With the implementation of ultrasonic vibrations, the temperature and strain rate were both increased during Al/Ti friction stir welding (FSW), leading to the formation of an amorphous interlayer, instead of intermetallic compound (IMC), at the interface. The interfacial microcracks were eliminated in the ultrasonic vibrations assisted friction stir welding (UVFSW). There were Ti particles separated from the Ti substrate and dispersed in the Al alloy, thereby resulting in a more gradual and moderate evolution of the interfacial microstructure. Due to the improved interfacial microstructure with ultrasonic vibrations, the lap shear strength was almost twice that of the conventional FSW welds within same welding conditions. Meanwhile, ultrasonic vibrations also improved the fabrication efficiency with a higher optimal traversing speed. The failure mode shifted from interface separation of FSW welds to a shear dimple fracture of the UVFSW welds, demonstrating the better plasticity and reliability of the UVFSW Al/Ti dissimilar joints.

Control factor optimization for friction stir processing of AA8090/SiC surface composites

Friction Stir Processing is a state-of-the-art technology for microstructure refinement, material property enhancement, and surface composites fabrication. This investigation concentrates on AA8090/SiC surface composites produced via friction stir processing. Experiments were conducted by varying the following friction stir processing parameters: Tool rotational speed (800–1400 rpm), Tool traverse speed (25–75 mm/min), and Groove width (1.0–1.8 mm). Response measures encompassed Ultimate Tensile Strength and surface roughness. Central Composite Design of Response Surface Methodology designed the experiments and mathematical relationships established between input parameters and ultimate tensile strength and surface roughness. Analysis of variance was used to test the model's adequacy. The models examined individual and interaction effects of input factors on ultimate tensile strength and surface roughness of surface composites. A combinations of input parameters was identified that yields the maximum ultimate tensile strength and minimum surface roughness. The current work employs the friction stir processing approach to synthesis near-net-shaped surface composites without additional machining by systematically optimizing process parameters. Results indicate that increasing tool rotational speed produces well-finished AA8090/SiC surface composites with decreased strength. In contrast, increased tool traverse speed and groove width generate surface composites with rougher surfaces and higher strength. Surface and contour plots further explored the influence of parameter interactions on responses.

Investigation of Mechanical Properties, Fretting Wear, and Corrosion Behaviour of AA6063/Si3N4 Nanocomposites Fabricated via Friction Stir Processing

Investigation of Mechanical Properties, Fretting Wear, and Corrosion Behaviour of AA6063/Si3N4 Nanocomposites Fabricated via Friction Stir Processing

Preparation of high-tensile-ductility and high-conductivity alumina dispersion-strengthened copper via a cold spray additive manufacturing-friction stir processing composite process

The solid-state forming capabilities of cold spray additive manufacturing (CSAM) offer a new method for creating nano-reinforced materials. However, the interface of the deposits often fails to form strong metallurgical bonds, leading to mechanical defects that weaken the material. This study investigates the preparation of highly plastic nano-alumina dispersion-strengthened copper by combining CSAM with friction stir processing (FSP), both solid-state techniques. The results show that FSP treatment fuses the interfaces of the deposited particles, transforming the microstructure from multi-scale, elongated grains to a uniform ultrafine-grained (UFG) structure. The average grain size reduces from 3.1 μm to 0.86 μm, and the proportion of high-angle grain boundaries increases from 42.5 % to 85.2 %. This treatment significantly enhances both mechanical and electrical properties. The ultimate tensile strength increases from 210 MPa to 450 MPa, elongation at break improves from 1 % to 35 %, and electrical conductivity rises from 70 % IACS to 81 % IACS. These findings demonstrate the potential of the combined CSAM-FSP approach for producing high-performance nano-alumina dispersion-strengthened copper with superior mechanical and electrical properties.

Investigation of tool traverse speed on surface integrity of nano composites processed by friction stir process

This work examines the effects of different tool traverse speeds on the surface integrity of AA7075 reinforced with graphene oxide (GO), silicon carbide (SiC) and graphene nanoplatelets (GNPs) nanoparticles during Friction Stir Processing (FSP). Three different traverse speeds of 20, 25 and 30 mm/min, respectively, were used for FSP operations. The resulting nanocomposites were thoroughly analysed using methods including optical microscopy, tensile testing, fracture morphology analysis, microhardness testing, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (FESEM-EDAX) and non-contact surface interferometry. The results show that the creation of a refined microstructure with equiaxed grains was aided by tool traverse speeds between 20 and 25 mm/min. Notably, an Ultimate Tensile Strength (UTS) of 358 MPa, microhardness of 139 HV, refined crystalline size of 47.162 nm and average roughness (Ra) of 1.53 μm were obtained with the AA7075+SiC nanocomposite under tool traverse speed of 25 mm/min. On the contrary, surface layer defects developed at a traversal speed of 30 mm/min. Through the use of mechanical stirring and severe plastic deformation (SPD), this study aids in changing the microstructure of the airplane frames.

Machine learning classification applied to the effect of AFSD process parameters on tensile properties

Additive Friction Stir Deposition (AFSD) is a key technology in additive manufacturing, where process parameters greatly impact deposition layer properties. Currently, there is no established method for systematically improving these properties through parameter investigation. This study addresses this by applying six machine learning (ML) classification algorithms to a dataset of 130 samples, classifying the ultimate tensile strength (UTS) based on feed rate, rotational speed, and downforce. The Support Vector Machine (SVM) algorithm achieved the highest accuracy at 95.3%. This research provides a precise method for classifying AFSD process parameters and demonstrates the potential of ML techniques for optimizing manufacturing processes, presenting a novel approach to enhancing AFSD deposition layer performance.

Effect of Back Plate Preheating Assistance System and Deep Rolling Process on Microstructure Defects and Axial Force Reduction of Friction Stir Welded AA6061 Joint.

This study investigates the effects of a back plate preheating assistance system and deep rolling (DR) on axial force and tunnel defects during friction stir welding (FSW). Different preheating configurations-advancing side (AS), retreating side (RS), and both sides-were examined to evaluate their impact on axial force reduction, temperature distribution, and defect minimization. Axial force measurements were taken using a dynamometer, and temperature histories were recorded with a thermal camera. The results demonstrate that a preheating temperature of 200 °C is optimal, reducing axial force by 30.24% and enhancing material flow. This temperature also facilitated deeper tool penetration, especially when preheating was applied to both sides. Preheating on the AS resulted in the smallest tunnel defects, reducing defect size by 80.15% on the RS and 96.91% on the AS compared to the non-preheated condition. While DR further reduced tunnel defects, its effectiveness was limited by the proximity of defects to the surface. These findings offer significant insights for improving the FSW process.

Friction stir welding of AA2024-T3 and SS304 alloys: microstructural analysis, microhardness evaluation, and tensile performance

This study examines the feasibility of friction stir welding (FSW) for dissimilar butt joints formed between 3 mm thick 2024-T3 aluminum alloy and AISI 304 stainless steel. It explores the impact of operational parameters, particularly traverse speeds of 20 and 40 mm min−1, a fixed tool rotation speed of 450 rpm, a tool pin offset of 1.5 mm, and a tool shoulder diameter of 18 mm, on microstructure, microhardness, and tensile strength. A traverse speed of 40 mm min−1 resulted in a lower peak temperature of 257.75 °C, while optimal conditions at a speed of 20 mm min−1 led to peak temperatures of 356.5 °C. This higher temperature facilitated material deformation, improved flow, enhanced mixing, and contributed to grain refinement, with an average grain size of 4.2 μm. Vickers microhardness tests revealed a maximum hardness of 339 Hv at a traverse speed of 40 mm min−1 and 413 Hv at 20 mm min−1. The ultimate tensile strength (UTS) reached 338 MPa, resulting in a joint efficiency (JE %) of 76.81% for the weld performed at optimal conditions.

On the effect of Zn, Cu, and brass interlayers in friction stir welded St37 and AZ31 dissimilar joints

On the effect of Zn, Cu, and brass interlayers in friction stir welded St37 and AZ31 dissimilar joints

Experimental optimization of the FSW parameters to weld the dissimilar Al- and Cu-alloys by using additives at their joints

Friction stir welding (FSW) stands as a promising technique for joining materials, offering advantages over conventional methods. This study investigates the influence of tool tilt angle, rotational speed and profile on welded joint characteristics using a design of experiment (DOE) approach. The research objective aims to determine optimal parameter combinations for improved mechanical properties. Methodology entails the systematic variation of tilt angle, rotational speed and tool profile in a DOE setup, with subsequent FSW of samples. Mechanical testing, including tensile, bend and hardness tests, is conducted on 24 samples, with scanning electron microscope (SEM) and microstructure analysis on two specimens. Results reveal that higher tilt angles, rotational speeds and threaded profiles yield increased tensile strength but decreased ductility. Similarly, bend tests show higher fracture loads but reduced deflection before fracture under these conditions. Hardness tests indicate elevated hardness in welded areas, with variations based on input parameters. Main findings highlight the importance of parameter optimization for desired mechanical properties. Lower tilt angles and rotational speeds promote smoother material flow and uniform heating, resulting in consistent microstructure and hardness distribution. In conclusion, this study provides valuable insights for optimizing FSW parameters to achieve desired mechanical properties in welded joints. The combination of a 2° tilt angle, threaded tool profile and 1500 rpm rotational speed demonstrated the highest tensile strength, while a 1° tilt angle, cylindrical tool profile and 1000 rpm rotational speed yielded highest ductility.

Precipitate Structure, Microstructure Evolution Modeling and Characterization in an Aluminum Alloy 7050 Friction Stir Weld

Precipitate Structure, Microstructure Evolution Modeling and Characterization in an Aluminum Alloy 7050 Friction Stir Weld

Experimental Investigation of Hardness and Surface Roughness in the Friction Stir Welding of the 6061-T6 Aluminum Alloy

Experimental Investigation of Hardness and Surface Roughness in the Friction Stir Welding of the 6061-T6 Aluminum Alloy

Effect of processing sequences in multi-pass friction stir processing on microstructure, microtexture and microhardness of 6063 aluminum alloy

ABSTRACT Single and double direction stir processing sequences were employed and investigated by fixing all other FSP parameters. Optical microscopy (OM) was utilised to assess the size and geometry of the processed zone. EBSD was also employed to evaluate the microstructure and microtexture development in different regions of the processed zones. In addition, Vickers microhardness measurements were made to evaluate the hardness evolution across the processed zone for the two processing sequences. The results show that using a single direction processing sequence is preferable due to better grain refinement, mainly in all regions of the processed samples. Gradual improvement was observed in microhardness with each additional pass, stronger refinement, and homogeneous grains in the processed regions (stir and overlapping zones). In the first pass’s stir zone (SZ), the microhardness is approximately 42.5Hv, while it increases to an average of 43.4Hv in SZ2 of the second pass and 44.3Hv in SZ3 of the third pass. Furthermore, more resistance to plastic deformation (slip) and lower intensity of heat distribution when compared to the double direction. Therefore, the application of a single direction processing sequence can be beneficial in the welding of such aluminium alloys.

Heat Mapping and Plastic Strain Radius Modeling of Dual-Tool Friction Stir Welds 6061 Aluminum Alloy Plate Using FEM

This study investigates the effects of Dual-Tool Friction Stir Welding (DT-FSW) parameters on the weld quality of 8 mm thick 6061 aluminum alloy plates, specifically focusing on the elimination or minimization of the "pass-overlap zone" that’s a gap typically observed at the mid-section of the weld cross-section resembling characteristics of the Heat-Affected Zone (HAZ). To address ongoing debates regarding the optimal joint performance concerning this overlap, symmetric increases in the dimensions of both FSW tools were implemented to analyze resultant temperature fields and plastic strain adaptations at the weld interfaces. Simulation visualizations were conducted with tool density variations at intervals of 0.2 mm and 0.4 mm. Results indicate that increasing tool density, thereby reducing the distance between tool surfaces, leads to a decrease in peak temperatures generated during welding. This reduction in temperature correlates with a more uniform distribution of plastic strain rates across all layers of the material—upper, middle, and lower—with the leading edge exhibiting the most significant improvement in strain uniformity. Conversely, during the stabilization phase, a decrease in tool density (S) results in a reduction of the maximum equivalent plastic strain rate. These findings suggest that careful adjustment of tool density in DT-FSW processes can enhance weld quality by promoting more uniform mechanical and thermal properties across the joint.

Superplastic behavior of a metastable β-type Ti alloy governed by grain size: Microstructure evolution and underlying deformation mechanism

The superplastic forming (SPF) technology has gained widespread adoption in the manufacturing of intricately shaped components made from Ti alloys with high dimensional accuracy due to its near net forming capabilities. It is crucial to systematically investigate the superplastic behavior in metastable β-type Ti alloys. However, the microstructure evolution and underlying superplastic deformation mechanism governed by grain size in these alloys remain unclear. In this study, three types of fine-grained (<10 μm) Ti-15V-3Cr-3Sn-3Al (Ti-15-3) alloys were obtained using friction stir processing (FSP), and tensile tests were conducted at temperature of 650 °C with strain rates ranging from 1 × 10−4 s−1 to 3 × 10−3 s−1. The deformation behavior of the coarse-grained (>3 μm) Ti-15-3 alloy can be described as quasi-superplastic rather than strictly superplastic. In this microstructure, plasticity is synergistically contributed by grain boundary sliding (GBS), continuous dynamic recrystallization (CDRX), and dynamic phase transformation (DPT). For the fine-grained (<3 μm) Ti-15-3 alloy, deformation enters into the superplastic region with GBS becoming the predominant deformation mechanism accompanied by DPT. Additionally, strain/stress promotes α phase precipitation from the β matrix, which inhibits grain growth and serves as a supplementary stress accommodation mechanism facilitating continuous operation of GBS and ultimately achieving exceptional superplasticity.

Microstructure evolution and grain refinement in 2319 aluminium alloy via wire arc additive manufacturing coupled with multi-pass friction stir processing

The present study investigates the alterations in 2319 aluminium alloy microstructure and properties induced by the WAAM-FSP process, including grain size, microhardness and tensile strength. The effects of multiple stirring friction processing and remelting on the grains were systematically investigated. The results demonstrated that the grains within the stirring zone underwent enlargement due to thermal remelting, while the size of the stirring zone decreased. Furthermore, multiple thermo-mechanical factors significantly intensified grain growth in the bottom of the stirring zone, resulting in an increase of up to 3.4 μm.Upon a second remelting process conducted on the top of the sample, the grain size in the stirring zone can reach 3.7 μm. Additionally, the bottom stirring zone exhibited a higher prevalence of deformed grains (21.7 %) of deformed grains caused by the extrusion during multiple stirring friction processing. The top region was subjected to less thermo-mechanical influence, resulting in a smaller grain size and an ultimate tensile strength of 192.6 MPa and a hardness of 90 HV0.2. This finding demonstrates highlights the impact of thermomechanical cycling on the grains within the multilayer samples prepared by the WAAM-FSP technique.

Effect of Feed Rate on Shear Strength and Macrostructure of Friction Stir Welding Dissimilar High Density Polyethylene-Polypropylene Joint

The connection of dissimilar materials is complicated, too. This connection is due to differences in physical and mechanical properties, but with the development of technology, dissimilar materials can be joined using solid-state welding methods. Dissimilar joints can produce a good combination of structure and mechanical properties. One of them is friction stir welding, which is used to connect sheet materials. The welding process of this research uses a conventional vertical milling machine. This study aims to determine the maximum shear strength and welding defects against variations in the feed rate of lap joints dissimilar high-density polyethylene with polypropylene. The machining parameters used in this experiment were 4 mm pin tool diameter, 2360 rpm rotation speed, 9 mm/min, 12 mm/min, and 16 mm/min feed rate. The results showed that the highest shear strength was obtained using the 12 mm/min feed rate variation of 3.11 N/mm. It can be seen in the macrostructure that the incomplete defects produced are less than the other welding process variations.

Convex structure formation on a Cu substrate by friction stirring using a tool wrapped with Ti foil

The bond strength between Cu substrate and epoxy resin is required to be improved in power modules. Surface modification of the Cu substrate improves the bond strength due to the anchor effect. In this study, we propose a new surface modification method using friction stirring. A convex structure was formed on a Cu substrate by friction stirring using a tool wrapped with Ti foil. The microstructure of the modified surface and adhesion with epoxy resin were evaluated. Friction stirring formed a Ti-derived convex structure on the Cu substrate, and Cu and Ti were mixed at the microscale and bonded strongly. The shear bond strength between the modified surface and epoxy resin was 7.9 ± 1.7 MPa, which was twice as strong as that without surface treatment. The Ti-derived convex structure formed on the Cu substrate improved adhesion with epoxy resin.