The joining of dissimilar AA2024 and AA6061 aluminium plates of 5mm thickness was carried out by frictionstirwelding (FSW) technique. Optimum process parameters were obtained for joints using statistical approach. Five different tool designs have been employed to analyse the influence of rotation speed and traverse speed over the microstructural and tensile properties. In FSW technique, the process of welding of the base material, well below it’s melting temperature, has opened up new trends in producing efficient dissimilar joints. Effect of welding speed on microstructures, hardness distribution and tensile properties of the welded joints were investigated. By varying the process parameters, defect free and high efficiency welded joints were produced. The ratio between tool shoulder diameter and pin diameter is the most dominant factor. From microstructural analysis it is evident that the material placed on the advancing side dominates the nugget region. The hardness in the HAZ of 6061 was found to be minimum, where the welded joints failed during the tensile studies.
The above tables and figures are showing that the results and main effect plots for mechanical properties of dissimilar joints of AA6061 and AA2014 using Tapered pin profile. From the Table4, The % Contribution of values for Tool Rotational Speed (70.6645), Welding Speed (15.3274) and Axial Force (3.2628). It is observed that the Tool Rotational Speed have great influence on Tensile Strength. Since this analysis is a parameter based design, from the above values it is clear that Tool Rotational Speed is the Major Factor to be selected effectively to get the good Tensile Strength., From the Table 5, The % Contribution of values for Tool Rotational Speed (27.311), Welding Speed (22.955) and Axial Force (2.9300). It is observed that the Tool Rotational Speed have great influence on Impact Strength. Since this analysis is a parameter based design, from the above values it is clear that Tool Rotational Speed is the Major Factor to be selected effectively to get the good Impact Strength From the Table 6, The % Contribution of values for Tool Rotational Speed (59.28), Welding Speed (11.03) and Axial Force (0.29).It is observed that the Tool Rotational Speed have great influence on Hardness. Since this analysis is a parameter based design, from the above values it is clear that Tool Rotational Speed is the Major Factor to be selected effectively to get the good Hardness.
Frictionstirwelding (FSW) is a novel solid state welding process for joining metallic alloys and has emerged as an alternative technology used in high strength alloys that are difficult to join with conventional techniques and which avoids bulk melting of the basic material, hot cracking and porosity. The function of FSW process are used in several industries such as aerospace, rail, automotive and marine industries for joining aluminium, magnesium and copper alloy. In aerospace industries most of the component is manufactured with aluminium material by welding process. Aluminium welding cannot be done by conventional process because temper characteristics of material will be changed. To overcome this drawback, frictionstirwelding process is selected. To investigate the effect of welding parameters and different tool pin profiles over FrictionStirWelding of dissimilarAA6061 and AA 7175 and also compare single pass frictionstirwelding and multi pass frictionstirwelding. The parameters considered were tool rotation speed, welding speed, tool pin profiles, tilt angle and number of passes. Different tool pin profiles are Threaded Triangular, Threaded Cylindrical, Threaded Hexagonal and Threaded Taper pin profiles plays a vital responsibility in deciding the weld quality. This work includes tensile tests, hardness test and impact test. .
The material used in this investigation was AA6061-T6. The chemical composition of base metals are presented in Table 1.The rolled plates of 6 mm thickness were machined to the required size (100 mm X 50 mm) welding was carried out in butt joint configuration using frictionstirwelding machine. The welding direction was aligned normal to the rolling direction, the welded joints were machined to the required dimensions as shown in Fig. 2. Tensile specimens were fabricated as per the American Society for Testing of Materials (ASTM E8M-04) standards  to evaluate the tensile properties of the joints. As prescribed by the design matrix, totally twenty joints of each alloy were fabricated in this investigation. The photographs of some of the fabricated joints are displayed in Fig. 3.
Frictionstirwelding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. In this work, similar frictionstirwelding between 7075-WC aluminum metal matrix welds alloy was investigated. The Frictionstirwelding between these two similar metals were produced at different tool rotational speeds with constant feed rate. The tool rotational speed was varied between 700 and 1500 rpm. The visual inspection and the x-ray radiographic testing techniques were conducted on the welds to ascertain the joint integrity before characterization to have an idea of the quality of the welds. Chemical analysis was carried out to attain the chemical composition at the weld nugget.
Table 3.1 FSW machine specification 46 Table 3.2 Chemical Composition of AA 5052 and AA 6063 alloys 48 Table 3.3 Mechanical Properties of AA 5052 and AA6063 alloys 48 Table 3.4 Chemical Composition of AA2024 and AA 7075 alloys 49 Table 3.5 Mechanical Properties of AA2024 and AA 7075 alloys 49 Table 3.6 Process Parameters for AA5052 and AA6063 50 Table 3.7 Process Parameters for AA2024 and AA7075 50 Table 4.1 Groove size in mm 66 Table 4.2 Properties of welded joint with different groove size 72 Table 4.3 Experimental plan for AA5052 and AA6063with copper
Several studies of the joining of aluminum alloys to steels by frictionwelding have been reported. Okita et al.,  who used transmission electron microscopy (TEM) with an energy dispersive spectroscopy (EDS) analysis attachment, investigated the interdiffusion of each element at the weld interface between pure aluminum and steel. Ochi et al. studied the frictionwelding of carbon steel to an Al-Mg-Si alloy using a filler metal of pure aluminum, and also reported the effect of welding parameters on the mechanical properties of joints comprising an Al-Mg-Si alloy and an Al-Cu alloy with stainless steel and carbon steel, respectively. Yashan et al. suggested that the bond strength of the inner part was different from that of the outer part in a pure aluminum- stainless steel friction weld joint. The inter diffusion behavior of each element at the weld interface and the frictionwelding process of commercial pure aluminum and 6061 aluminum alloy. to stainless steel joints were investigated using SEM and ultrasound microscopy by the present authors The conclusions of the above studies1 to 18 were that, in the case of aluminum alloy-steel frictionwelding, the welding mechanism was based on diffusion bonding in the solid state, welding progressed from the outer to the inner part, and the reaction layer was mainly composed of (Fe,Cr,Ni) 2Al5. Moreover, excess formation of intermetallic compounds at the weld interface degraded the joint strength. However, the evolution of the frictionwelding process and the reaction layer growth behavior, and the relationship between them, were not fully clarified.
The hardness traverses of joints at a travel speed of 100 mm/min measured are presented in Fig. 7. In the stir zone of the Al alloy, the hardness was partly increased by Ti alloy chips. The hardness near the joint interface of the Ti alloy side was higher than that of the Ti alloy base metals. This region with a higher hardness near the interface of the Ti alloy side was much wider than that of the mixed region observed by SEM and EDS. Hence, it is considered the cause of the increased hardness in the Ti alloy side observed near the joint interface is not the formation of an intermetallic compound. It is due to the plastic deformation of the Ti alloy Ti
Boumerzoug and Helal  studied the microstructure and strength properties of frictionstir welded 6061-T6 aluminium alloy to ultra-low carbon steel using different advancing speeds of 100, 200, and 400 mm/min at constant rotation rate. The advancing speed effect on the microstructure and strength properties of the welded dissimilar materials has shown that phenomenon of grain refinement is developed in the aluminium side. Khan et al.  studied mechanical and microstructural behaviour of frictionstir welded similar and dissimilar sheets of AA2219 and AA7475 aluminium alloys. Frictionstirwelding process has been employed to join similar and dissimilar 2.5 mm thick sheets of AA2219-O and AA 7475-T73 aluminium alloys. Grain refinement is observed at the stir zone due to dynamic recrystallization caused by severe plastic deformation. Lowest strength for dissimilar joint is observed primarily due to non-homogeneous movement of base materials consequent to differences in mechanical and physical properties. Minimum hardness was found at TMAZ retreating side for all joints due to the thermal softening.
The investigation is on effect of welding parameters on the microstructure and mechanical properties of frictionstir welded butt joints of dissimilar aluminium alloy sheets between Semi- Solid Metal (SSM) 356 and AA6061-T651 by a Computerized Numerical Control (CNC) machine. The base materials of SSM 356 and AA6061-T651 were located on the advancing side (AS) and on the retreating side (RS), respectively. FrictionStirWelding (FSW) parameters such as tool pin profile, tool rotation speed, welding speed, and tool axial force influenced the mechanical properties of the FS welded joints significantly. For this experiment, the FS welded materials were joined under two different tool rotation speeds (1,750 and 2,000 rpm) and six welding speeds (20, 50, 80, 120, 160, and 200 mm/min), which are the two prime joining parameters in FSW. A cylindrical pin was adopted as the welding tip as its geometry had been proven to yield better weld strengths. From the investigation, the higher tool rotation speed affected the weaker material’s (SSM) maximum tensile strength less than that under the lower rotation speed. As for welding speed associated with various tool rotation speeds, an increase in the welding speed affected lesser the base material’s tensile strength up to an optimum value; after which its effect increased. Tensile elongation was generally greater at greater tool rotation speed. An averaged maximum tensile strength of 197.1 MPa was derived for a welded specimen produced at the tool rotation speed of 2,000 rpm associated with the welding speed of 80 mm/min. In the weld nugget, higher hardness was observed in the stir zone and the thermo-mechanically affected zone than that in the heat affected zone. Away from the weld nugget, hardness levels increased back to the levels of the base materials. The microstructures of the welding zone in the FS welded dissimilar joint can be characterized both by the recrystallization of SSM 356 grains and AA6061-T651 grain layers .
A number of studies have been conducted on FrictionStir Spot Welding between Aluminium alloys over the years. Uematsu et al , joined T4 treated 6061 using a double- acting tool consisting of outer flat shoulder and inner retractable probe, which could re-fill probe hole. The microstructures of the weld zone were classified into MZ (mixed zone) and SZ, where fine equiaxed grains were observed due to dynamic recrystallisation during FSSW process. They further found that the tensile strength of the joint was improved by a re-filling process because the effective cross sectional area of the nugget was increased .
However, the dissimilar FSW involved with UFGed materials has never been reported according to the best of our knowledge. The FSW of dissimilar alloys has been significantly studied including dissimilar aluminum alloys, Al/Mg alloys, Al/Steel pairs, etc. The main salient feature of FSW of dissimilarmetals and alloys is thought to be the variation in asymmetry or the degree of symmetry with reference to the weld centerline [ 16 ]. For example, Lee et al. evaluated the joint microstructure of the dissimilar welds between cast A356 and wrought 6051 aluminum alloys produced at various welding speeds [ 17 ]. Palanivel et al. [ 18 ] studied the effect of the tool rotational speed and pin profile on the microstructure and tensile strength of dissimilar FSW between the AA5083-H111 and AA6351-T6 aluminum alloys. They found that joint strength was affected due to the variations in the materials behavior. It is evident that an important aspect in the FSW of dissimilar materials is the selection of the appropriate alloys for the advancing and the retreating sides to obtain the optimum mixing and weld properties due to the asymmetric material flow in the joints. It was found that the maximum tensile strength was achieved for the dissimilar FSW AA2024/AA7075 aluminum alloy joints only when the 2024 Al alloy was located on the advancing side [ 19 ]. Kwon et al. successfully obtained Al/Mg dissimilar FSW joints when the AZ31 alloy and Al alloy were located on the RS and AS, respectively. However, the reason of the work-piece configuration was not explained in detail [ 20 ]. According to the investigation of dissimilar FSW between Al and Cu alloys, the suitable configuration and even the amount of offset of the tool from the joint centerline were considered to play an important role in obtaining high joints properties [ 21 – 23 ]. More recently, Sun et al. conducted the dissimilar spot FSW between the UFGed 1050Al and 6061-T6 aluminum alloys [ 24 ]. However, the UFGed materials have not been reported to be dissimilar FSW processed with other materials.
Welding is the main joining method for these materials. Many welding methods for Aluminium and its alloys have been reported [2,3,4], these methods include tungsten arc welding (TIG), metal inert gas welding (MIG), laser welding, and frictionstirwelding (FSW). It is widely accepted that the mechanical and corrosion properties of welded Aluminium alloys are influenced by the welding process. Welding process exhibited a partially melted zone (PMZ), in other words heat affected zone (HAZ) adjacent to the fusion zone (FZ) where the metals melt and solidify, beyond the HAZ is that part of the metal which has not been subjected to thermal alteration and it is called the base or parent metal (BM). The formation of these zones is usually caused by the heat generated during the welding process. Such heat may alter the microstructure of AA . Wadeson et al  found that the corrosion resistance of the welded materials at different regions that formed during the welding process is not the same; their study showed that the welded zones of most joints are susceptible to corrosion. Welding of Aluminium and its alloys is considered to be challenging because lots of difficulties are associated with this kind of joining, the main important difficulties are related to the presence of oxide film on the surface, high thermal conductivity, solidification shrinkage, formation of defects, and more important is the solubility of hydrogen and other gases in molten state . The presence of these difficulties and challenges has motivated us to conduct the current research and others in order to have a better understanding.
FrictionStirWelding (FSW) is a solid state welding process that uses a third body (tool) to join two faces of the work pieces. Heat is generated between the tool and work piece material due to friction of the tool shoulder with the work piece surface. This leads to rise in temperature which makes the material soft near the FSW tool. Then, both the work piece materials mechanically intermix at the place of the joint to produce the welding. FSW has been successfully used to join similar as well as dissimilar materials. It has also been effectively used to join materials that are difficult-to-weld materials by conventional fusion welding methods. Fusion welding when used to join dissimilarmetals leads to defects like lack of fusion, distortion, crack formation, incomplete penetration and undercut. FSW, being solid state welding process, can successfully eliminate most of the defects which occur due to melting of material during welding. Some of the important parameters in FSW are tool rotation speed, transverse speed, tool pin dimension, tool tilt angle, offset of the tool from weld line and tool pin profile. From literature survey it was observed that these parameters affect the quality of weld. So, the influence of the parameters is needed to be established on the weld quality. In this context, the present work highlights the significance and effect of tool rotation speed, welding speed, tool pin profile and offset of the tool on weld quality. Different destructive and non-destructive tests have been carried out on the weld to get insight into the weld and its properties. Frictionstir spot welding (FSSW) is a type of FSW, which is used to create a spot weld. The effect of tool rotation speed, dwell time and tool pin dimension has been investigated on spot welding of different materials. Three types of welding have been done in FSSW: similar metals, dissimilarmetals and metal-polymer. Face centred central composite design of response surface methodology has been implemented to design the experimental layout for different experiments. Tensile strength test, bending strength test, visual inspection, radiography test and Vickers hardness test are the major tests that have been implemented on the weld to analyse the weld quality. Analysis of variance has been used to analyse the data, find the significant and non-significant parameters and estimate their effect.
Many researches on FSW joints showed that the elongations of as-welded joints are only between 20 to 40% of the base metal elongation (Hu, Yuan, Wang, Liu, & Huang, 2011). Using post weld heat treatment (PWHT) could be effective for improving joint mechanical properties. The PWHT can be solution heat treatment and then precipitation or just aging treatment in order to recover the loss of mechanical properties in the joint zone. A few studies on the PWHT of FSW aluminum alloys such as dissimilar joint AA2024 and AA 7075 or similar joint such as 7449 , 6061-O , 2219-O and 2024-T4 showed that the PWHT recovered a large portion of the lost strength in the nugget, but it comes with loss of ductility (Hu et al., 2011; Muruganandam, Raguraman, & Kumaraswamidhas, 2015). The investigations have proved that the fine recrystallized grains of nugget are instable and they become coarse grain structures after PWHT through abnormal grain growth (AGG) (Aydın, Bayram, & Durgun, 2010; Charit & Mishra, 2008; Sullivan & Robson, 2008).
The joining of dissimilar AA2024 and AA5056 aluminium plates of 5mm thickness was carried out by frictionstirwelding (FSW) technique. By using statical approach Optimum process parameters were obtained for joining two different material. To analyse the influence of rotation speed and traverse speed over the microstructural and tensile properties Five different tool designs have been used. By using FSW technique, the process of joining of the base material, well below it’s melting temperature, has opened up new trends in producing efficient dissimilar joints. Analysis of welding speed on microstructures, hardness distribution and tensile properties of the welded joints were done. By changing the parameters of different process, defect free and high efficiency welded joints were produced. Keyword: FSW , Welding, DissimilarMetals.
The basic principal of Frictionstirwelding is heating the metal to a temperature below re-crystallization temperature using Friction generated by the cylindrical shouldered tool on metal. This tool having characteristic profile pin, which is rotated and pushed into the joint area between two pieces of sheet or the plate material. The parts have to be done secure clamping using the fixtures to prevent the joint faces from being forced apart. The Frictional heat is produced between the wear-resistant welding tool and the experimental work pieces, which causes the metals or alloys to soften without reaching the melting point. The tool moves along the joint line of the work materials. The plasticized material gets transferred to the moving edge of the tool pin and forced through similar contact with the tool shoulder and pin profile. The cooling of the material leads to the creation of a solid phase bond between the clamped work pieces.
welding are low distortion, absence of melt related defects and high joint strength. Tool design and material plays a vital role in addition to the important parameters like tool rotational speed, welding speed and axial force. Aluminum alloys are important for the fabrication of components and structures which require high strength, low weight or electric current carrying capabilities to meet their service requirements. Among all aluminum alloys, AA6061 alloy plays major role in the aerospace industry in which magnesium and silicon are the principal alloying elements. As the FSW process does not release toxic acids or fumes, it is an environment protective process. No consumable filler material or edge preparation is normally necessary. The distortion is significantly less than that caused by arc fusion welding techniques. By welding Aluminum alloys by fusion welding process there is possibility of cracks, porosity, alloy segregation and hot cracking and the fusion welding process completely alters microstructure and varies the mechanical properties. By FSW both similar and dissimilar materials can be successfully joined. The parameters like welding speed, tool rotational speed, axial force, tool profile has affect on the weld. From the results obtained it can be inferred that tool rotational speed and welding speed has got influence on the welded joint.
The optical microstructure of the diverse zones of the welded dissimilar material is shown in Fig. 2. Though the weld region undergoes a significant amount of thermal cycle, there is a considerable changes occurred in the microstructure of the base metals. On the other hand, the thermal cycle is considerably influenced the Heat affected Zone (HAZ), which is evident from the microstructure Fig 6. However, there is a plastic deformation occurring in this area. In the thermo-mechanically affected zone (TMAZ), there is considerable growth in the grain boundaries which is due to the plastic deformation and the less heat developed during the process. Additionally, it is obvious from the microstructure that a particular grain limit isolates the recrystallized zone (weld chunk) from the disfigured zones of the TMAZ. The dynamically recrystallized zone is the stirred zone, where the material has undergone severe plastic deformation resulting in fine equiaxed grains . The term stirred zone is commonly used in frictionstirwelding, where sufficient volume of material is stirred. Further from the microstructure of the weld nugget Fig.6, it is evident that the grains are highly refined, which could
Frictionstirwelding (FSW) is a solid state joining process developed at The Welding Institute (TWI), Cambridge, UK, in 1991. The process uses rotating tool which provides frictional heat and mixing to produce a weld between two metallic surfaces below their melting point. Since the process works below the melting point of the metals some of the defects like cracks, porosity and blow holes arising out of fusion welding process are eliminated. Koilraj et al  investigated the optimum values of dissimilarfrictionstirwelding process parameters such as tool rotational speed, transverse speed, tool geometry and ratio between tool shoulder diameter and pin diameter for aluminium AA2219- T87 and AA5083-H321 alloy. The results indicated that optimum levels of the rotational speed, transverse speed, and D/d ratio are 700 rpm, 15 mm/min and 3 respectively. The cylindrical threaded pin tool profile was found to be the best in contrast to other profiles. The D/d ratio contributes 60% to the satisfactory welds.Govind Reddy et al  optimized the process parameters on the work on dissimilar frictions stirwelding using AA2024-AA7075 aluminum alloy. In this work effect of tool rotation speed and welding speed on the tensile strength is investigated by developing mathematical model using response surface methodology and Nelder Mead algorithm.R Palanivel et al  studied the effects of tool rotational speed and pin profile on microstructure and tensile strength of two different aluminum alloys AA5083-H111 and AA6351-T welded by using frictionstirwelding under varying process parameters with different tool pin profiles. The results showed that the joint fabricated by Straight Square at the tool rotational speed of 950 rpm yielded highest tensile strength of 273 MPa. The two process parameters affected the joint strength due to variations in material flow behavior, loss of cold work in the HAZ of AA5083 side, dissolution and over aging of precipitates of AA6351 side and formation of macroscopic defects in the weld zone.D. A. Dragatogiannis et al  did the work on