In the published work by Colegrove and Shercliff  , the application of the computationalfluid dynamics (CFD) code, was described to modelling the 3-dimensional metal flow in frictionstirwelding(FSW). The primary goal was to gain a better understanding of the material flow around a complex FSW tool and demonstrate the effects of tool rake angle and the rotation speed. To do this, a flow model was developed that included coupled thermal and flow analysis, heat generation by viscous dissipation, heat loss to the backing plate and the tool, convective heat loss from the top surface of the plate. As it is able to handle the high strain rates that occur near the tool surface, the CFD package FLUENT  was selected for the modeling work. To solve the model, the problem was considered a steady state, and the material sticks to the tool surface. As a result, it was noted that streamlines are instantaneously tangential to the flow and the particle tracks are much more difficult to calculate and require a full transient analysis. Regarding the longitudinal streamlines show very little deviation in height as the material passes the tool. This contrasts with the quite large vertical movement of material as compared to the literature. The problem is caused by the model’s over-prediction of the deformation region size.
A computationalfluid dynamics (CFD) model is presented for simulating the material flow and heat transfer in the frictionstirwelding (FSW) of 6061-T6 aluminum alloy (AA6061). The goal is to utilize the 3-D, numerical model to analyze the viscous and inertia loads applied to the FSW tool by varying the welding parameters. To extend the FSW process modeling, in this study, the temperature-dependant material properties as well as the stick/slip condition are considered where the material at the proximity of the FSW tool slips on the lower pressure regions. A right-handed one-way thread on a tilted FSW tool pin with a smooth, concaved shoulder is, additionally, considered to increase the accuracy of the numerical model. In addition, the viscous and frictional heating are assumed as the only sources of heat input. In the course of model verification, good agreements are found between the
Investigations at the micro-mechanical level were reported for aluminum alloy 6111 spot FSW joints welded with different processing times [408, 409]. Apart from microstructural studies and micro-hardness tests, a new approach to characterizing the distribution of the weld zone modulus using modal vibration tests on micron scale cantilever array specimens with a micro-scanning laser vibrometer and the corresponding FE simulations was developed. Micro-cantilever array samples were designed in such a way that each micro-cantilever represents one of the weld zones. Microscopic studies revealed a partial metallurgical bond formed in the direction of flow, which is governed by the tool used. The Vickers hardness numbers in those regions were found to be considerably lower than those of the base metal. Parametricstudies to determine the effect of weld zone measurements on the modal frequencies have been carried out using FE models. Deformation and fracturing in impulsively loaded FSW sandwich panels were studied . Micro-hardness and miniature tensile coupon testing revealed that FSW reduced the strength and ductility in the welds and in a narrow heat-affected zone on either side of the weld, by about 30%. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a FE analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. This comprehensive study reveals the existence of a strong instability in the loading that results from changes in sand particle reflection during the dynamic evolution of the panel's surface topology.
FrictionStirWelding (FSW) is a new joining process, which used frictional heat generated between rotational tool and material. FSW is a solid-state welding. Therefore, it has excellent properties such as low distortion and low residual stress. FSW is widely applied to linear joints. 1) When FSW becomes to be capable to nonlinear joints, it can be applied to many industries. 2,3) However, there are two problems that nonlinear FSW can’t be applied easily as below. (1) Occurrence of deviation from appropriate welding parameter made by complicated tool control. (2) Presence of unsteady welding condition area made by FSW parameter change. Such two problems are described as below.
Masayuki Aonumaa and Kazuhiro Nakatab carried out the experiment on the effect of alloying elements on the microstructure of dissimilar joints of a Mg–Zn–Zr alloy (ZK60) and titanium by using FSW. They did investigation on the effect of alloying elements of ZK60 Mg–Zn–Zr alloy on the microstructure of the dissimilar joint interface. Zn and Zr of alloying elements formed a thin reaction layer with titanium at the joint interface by frictionstirwelding.
The hardness profile in the age harden Aluminium alloy AA6063 strongly depended on precipitate distributions rather than on grain size. The minimum hardness region contained only a low density of rod-shaped precipitates, which led to the minimum hardness in that region accompanied by a loss of solute from the matrix. No precipitates could be detected in the softened regions because of dissolution of all precipitates during welding . Frictionstir welded AA 2024 joints exhibited a W- shaped hardness distribution that is characteristic of frictionstir welds in precipitation hardening aluminum alloys, the weld nugget was significantly harder than the thermos- mechanically affected region immediately outside the nugget boundary A quite strong local softening of the AA7075 - T6 occurred because of the thermal action of the welding process .
One of the first implementations of FSW was in the aerospace industries in the year 1998, when NASA began the process for use on the space shuttle external tank(ET).The repeatability and reliability of FSW, coupled with its ability to join lightweight alloys, makes the process efficient in the aerospace application. The technical maturation of this process for aerospace production at Marshall Space Flight Centre led to several noteworthy developments among them the implementation of a retractable pin tool(RPT) and frictionstir plug welding.The development of non- destructive evaluation(NDE) techniques for FSW was also driven by the process’s use on space vehicles[30,32]. In recent years, private aerospace companies have adopted the technology for their space applications.FSW is also rapidly gaining acceptance as a rivet replacement technology in the manufacture of aviation structure[33,34].In addition to weight savings, the use of FSW leads to a reduction in parts, reduced cycle times, greater joint strength, and lower manufacturing costs. In the private aviation sector, Eclipse Aerospace, developed an FSW process to join its 500 VLJ finding that FSW enabled joining speeds six times faster than automated riveting and 60 times faster than manual riveting[31,35].The Eclipse 500 has a total of 263 frictionstir welds that total 136m in length and replace 7378 conventional fasteners. The fatigue life of the FSW joints equals or exceeds the fatigue life of the FSW joints equals or exceeds the fatigue life of comparable riveted joints, easily exceeding the eight-lifetime cycle requirement[31,35] Many commercial aerospace manufacturers have also implemented the use of FSW has replaced rivets on longitudinal fuselage skin joints and wingspans for the A340, A350 and A380 aircraft.
ABSTRACT :- The comprehensive body of knowledge that has built up with respect to the frictionstirwelding (FSW) of aluminum alloys since the technique was invented in 1991 is reviewed on this paper. The basic principles of FSW are described, including metal flow and thermal history, before discussing how process parameters affect the weld microstructure and the likelihood of defects. Finally, the range of mechanical properties that can be achieved is discussed. It is demonstrated that FSW of aluminum is becoming an increasingly mature technology with numerous commercial applications.
FrictionStirWelding (FSW), being a novel process and facilitates welding various joints required for several industries mainly aerospace, marine, spacecraft, automotive, etc. It is an attractive solid state material joining technology, different to conventional welding methods, having ability to produce welds with higher integrity and minimum induced distortion, reduced porosity defect, reduced heat affected zone, no requirement of shielding gas, ecofriendly and minimum residual stresses etc. In this paper, a critical estimation of important features of frictionstirwelding namely process principle, selection of tool and workpiece material, metallurgical and mechanical aspects; effect of process parameters; methodology for optimizing the process parameters have been discussed. Further different applications of the process are presented along with critical review of literature; finally recognized areas of research work on materials such as AA6061 and Taguchi (L9) orthogonal array used as a methodology to optimize the process parameters for conditions to achieve better quality welds.
higher hardness value than the retreating side. Beyond the NZ, the hardness value decrease and the various regions the joint exhibited a similar hardness value of 170 HV. After T4 treatment, the hardness value increase and close to that of BM with temper. K. Kalaiselvan  studied the role of frictionstirwelding parameters on tensile strength of AA6061-B4C composites joints. The B4C reinforced aluminium matrix composites were fabricated by modified stir casting route. A high carbon high chromium (HCHCr) steel tool oil hardened to HRC 62 having square pin profile were used as FSW tool. The process parameters such as rotational speed (N), welding speed (S), axial load (F) and reinforcement (R) were considered. The process parameters were optimized using generalized reduced gradient method (GRG) method.
(Cambridge) in 1991 as a solid state joining technique and was initially applied to Aluminum Alloys (Dawes C and Thomas W, TWI Bull, 1995; Thomas W M, etal., 1991). FrictionStirWelding is a solid state joining process combining deformation heating and mechanical work to obtain high quality, defect free joints. FrictionStirWelding is especially well suited to joining Aluminum Alloys in a large range of plate thickness and has particular advantages over fusion welding when joining of highly alloyed Aluminum is considered.. The heat input into the material and the resulting welding temperature can be controlled by adapting process parameters like the down-force, rotational speed or welding speed as shown in Fig. 1
When welding the workpiece is rigidly fixed on the backplate, the tool begins to move along the welding seam under the high-speed rotation. The pin is inserted into the material for friction and stir. The shoulder is rubbed against the surface of the workpiece and is used to avoid spillage of the plastic material and serves to remove the oxide film on the weld boundary. During the welding process, the pin is rotated and inserted into the joint of the workpiece. The friction heat between the shoulder and the workpiece causes a strong plastic deformation of the material at the leading edge of the tool. As the tool moves, the material of highly plastic deformation gradually flows to the trailing edge of the tool, forming a frictionstirwelding seam. The requirements of frictionstirwelding equipment are not high, a milling machine can also achieve the rotation and movement of the tool. However, the rigidity requirements for welding equipment and fixtures are high. It should be noted that the end of the frictionstirwelding in the end will form the keyhole. A telescopic tool has been successfully developed for keyhole problems, and post-welding will not leave the keyhole. In addition, the movement of interface atoms in the welding process is still in the research stage.
The frictionstirwelding (FSW) process developed by the Welding Institute (TWI) of UK in 1991 is a novel solid- state joining technology that has broad applications in joining aluminum alloys difficult to weld by conventional fusion processes. Compared to other tradition-al welding techniques, FSW is considered to be an excellent eco-friendly technology due to its fine microstructure, absence of cracks and pores, free of shielding gas and filler metal, low residual stresses, and better dimensional stability [1,2]. Aluminum and aluminum alloys have become increasingly used in production of automobiles and trucks, packaging of food and beverages, construction of buildings, transmission of electricity, development of transportation infrastructures, production of defense and aerospace equipment, manufacture of machinery and tools and marine structures with its unique properties such as corrosion resistance, thermal conductivity, electrical conductivity, high strength with low density, fracture toughness and energy absorption capacity, cryogenic toughness, workability, ease of joining (welding (both solid state and fusion), brazing, soldering, riveting, bolting) and recyclability .
Further research has been conducted to understand the mechanical properties of frictionstir welded dissimilar aluminium alloys and other metals such as steel, magnesium, and aluminium composites. Kwon et al 5 performed FSW of different metals with different aluminium and magnesium. Strain rate hardening is similar for both materials at various strain rates and exhibits excellent material flow characteristics and load carrying capacity. Moreira et al 6 studied the weld ability of aluminium alloy 6061-T6 by 6082-T6 by FSW, and the mechanical properties were compared with the base material. Minak et al 7 compare weld quality of frictionstir welded aluminium alloy matrix composites with basic materials and correlate with microstructure modification. Chen et al 8 investigated the weldability, microstructure evolution and mechanical properties of AA6063 aluminium alloys and composites. More than 60% joint efficiency after artificial aging was observed and increased to over 80%.
Commercially pure titanium and titanium alloys such as Ti-6Al-2Sn-4Zr-2Mo alloy, Ti-6Al-4V alloy, Ti-8Al-1Mo-1V alloy are used in aerospace industries. Titanium alloys find application in the manufacturing of airframes and turbo fan engines . Lee et al.  investigated about the microstructure properties of FrictionStir Welded pure Titanium alloy. He observed that the grain structures of the weld zone were closely related to the hexagonal close packed (HCP) crystal structure of Ti. Liu et al.  studied about the microstructural characteristics and mechanical properties of FrictionStir Welded joints of Ti–6Al–4V titanium alloy. He observed that the joints had lower strength and elongation than the base material, and all the joints were fractured in the stir zone. This paper will discuss these papers [2-9] in a brief manner.
riction stirwelding is a new technique developed by The Welding Institute (TWI) for the joining of aluminum alloys . Frictionstirwelding (FSW) is a new metal joining process that is presently attracting considerable interest. The process is solid state in nature and relies on a localized forging of the weld zone to produce the joint. In this welding process, a rotating welding tool is driven into the material at the interface of, for example, two adjoining plates, and then translated along the interface and shown in the figure 1. Frictionstirwelding offers ease of handling, precise external process control and high levels of repeatability, thus creating very homogeneous welds. No special preparation of the work piece is required and little waste or pollution is created during the welding process. Furthermore, its applicability to aluminium alloys, in particular dissimilar alloys or those considered unweldable by conventional welding techniques, such as Tungsten Inert Gas (TIG) welding, proposes it as an attractive method for the transportation sector. Friction heats the material which is then essentially extruded around the tool before being forged by the high down pressure. The weld is formed by the deformation of the material at temperatures below the melting temperature. The simultaneous rotational and translational motion of the welding tool during the welding
Two FSW samples of 6-8 mm-thick hot rolled DH36 and two samples of 14-mm-thick EH46 steel grades were investigated; chemical composition as supplied by the manufacturer is shown in Tables 1 and 2. Frictionstirwelding has been carried out at TWI/Yorkshire by using PowerStir FSW machine; hybrid FSW PCBN tool (com- mercially known as Q70) with shoulder diameter of 24- and 5.7-mm probe length was used for welding 6- and 8-mm-thick plates. Another PCBN tool with diameter of 38- and 11-mm probe length was used for welding 14-mm- thick plates. Note that maximum plunge depth expected from this tool is 12 mm. The welding parameters including tool rotational/traverse speeds, plunge depth, torque, and forces are shown in Table 3.
Frictionstirwelding (FSW) is primarily used for aluminium also used for copper in certain industrial application. In the present study FSW of 5mm pure copper plates is done on vertical machining center with cylindrical H13 material tool. Surface temperatures are measured using pyrometer. Temperature graphs are plotted. The welded Joint at 950 RPM tool rotational speed and at 7mm/min tool traverse speed found satisfactory in visual inspection.
According to (Tanwar & Kumar, 2009), As a solid state process FSW eliminates many of the defects that usually occurred in fusion welding such as shrinkage, solidification cracking and porosity. Also, the bond between the two materials occurred uniquely of the original material, giving the welded material the comparable strength, bending and fatigue properties of the parent’s material. FSW is a new method that permanently joining metal in a greener way. This has been proven by Hassan et al, (2014) when an experiment was conducted between FSW and gas metal arc welding (GMAU). Both welding techniques were tested by welding pairs of 3mm thick aluminium strip. The parameter of each welding techniques was fixed and the aspects such as the welding quality, power input, macrostructure and microstructure of the welded joints were examined. Hence, the results obtained showed that the FSW was green, environment-friendly and more superior welding properties compared to the conventional GMAW.
Unlike fusion welding, FSW has only few process parameters such as tool rotational speed, tool traverse feed, plunge depth, tool geometry etc. which can be easily controlled to produce the good weld . Solid joint is produced as a result of this process. Because of different profile of tool geometry and features of the tool, the material movement around the pin can be quite complex . During FSW, the material subjected to intense plastic deformation at high temperature, which afterward resulting in generation of the equiaxed and fine recrystallized grains . Frictionstirwelding can be used for various types of joints such as lap joints, butt joints, fillet joints and T butt joints .