Commercial Al7075-T651 rolled plates 6.5 mm thick were cut to the required size (100 mm long and 50 mm wide) with the help of power hack saw and milling machine. The tensile testing of the base metal was done on 50 KN computer controlled universal testing machine (Make: Tinius Olsen) at room temperature with a constant head speed of 0.5 mm/min. The tested ultimate tensile strength of the base material was found to be 568 MPa. Non consumable tools made from M2 grade high speed steel with a cylindrical threaded pin were used to fabricate the joints. The tools were machined and then subjected to the standard heat treatment cycle for high speed steels to induce an hardness of upto 60 HRC. Close square butt joints were frictionstirwelded using a conventional vertical milling machine. The welding was done with a specially designed fixture made from SS304.The values of prominent parameters like welding speed and tool travel speed were selected on the basis of optimum values reported in the available literature. A tool tilt angle of 2 0 on the backward side is given to the welding tool. Providing a tilt angle to the tool mainly promotes recoalescence of the material in the stir zone at the rear of the tool. The experiments were carried out with three different shoulder diameter tools. The dimensions of the tools are shown in Figure 1. The process parameters selected for welding are shown in Table 1. During the welding process temperature data were continuously recorded at various locations in the plates using K-type thermocouples. After welding, all the welds were allowed to naturally age for the same period of time. The welds were visually inspected. This was followed by mechanical characterization which consists of tensile testing.
Frictionstir welding (FSW) is a 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. Tool geometry is very important factor for producing sound welds in FSW. Welding parameters, including tool rotation rate, traverse speed, spindle tilt angle, and target depth, are crucial to produce sound and defect-free weld. . The optimal tool design for welding steels, the effect of the tool shape on the mechanical properties and microstructures of 6061-T6 whose deformation resistance is relatively low, the tool shape does not significantly affect the microstructures and mechanical properties . The mechanical properties of Aluminium Alloy Al 6061 is Considering with different Parameters of FSW. Two different type of tool shapes and shoulder surfaces for single weld configurations were used in experiments. Tensile strength test showed that welding speed is the main parameter which affects the tensile strength. Feed rate and tool shape are affecting second and third respectively. As a result of the experiment the welding speed 600 RPM, Feed Rate 40 mm/min and taper probe tool are the best optimum levels to get maximum strength of mechanical properties . The mechanical properties of the welded joints of Aluminum alloys is focused . The welds were tested by liquid penetration test and the ultrasonic test, which reveals acceptance. The samples were tested by ASTM standards of tensile test, bending test, charpy impact test. The characteristics (load at yield, yield stress, tensile strength and load at sample failure) of frictionstirwelded material are discussed. The inertia friction welding is used to create joints between a 6061-T6 aluminum alloy and a AISI 1018 steel using various parameters. The joints were evaluated by mechanical testing and metallurgical analysis. Microstructural analyses were done using metallography, microhardness testing, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray elemental mapping, focused ion beam (FIB) with ultra high resolution SEM and transmission electron microscopy (TEM) in TEM and STEM modes. Results of these analysis first suggested that joint strengths on the order of 250 MPa could be achieved . The microstructure and mechanical properties are evaluated on frictionstirwelded butt joints of aluminum alloys. Microstructure analysis of the cross-section of the joints revealed distinct lamellar bands and various degrees of
Properties like light weight, high strength-to-weight ratio, and good corrosion resistance make aluminiumalloys widely accepted in automotive industry. The low melting point of these alloys makes welding by traditional methods difficult due to the imperfections associated with fusion processes. Frictionstir welding (FSW) is a solid-state welding method invented in 1991 at the welding institute (TWI) in the UK; melting and recasting do not occur when using this process. But joints from AA6061-T651aluminium alloy have been frictionstirwelded with different welding parameters like tool rotational speed and tool welding speed with constant tool dimension. The effects of rotational and welding speeds on the tensile strength, microhardness distribution and microstructure of the welding joints were studied. The results showed that the maximum tensile strength of the joints can be achieved when using tool with 18 mm and 5 mm shoulder and pin diameter at 710 rpm tool rotational speed and 23 mm/min. Also, we observed that microhardness is markedly affected when tool rotational speed increases.
transportation as well as low heat generation by plastic deformation and friction at tool/workpiece interface may be responsible for producing poor quality of welds. Yuqing et al.  observed that tool pin profile could significantly influence material flow and peak temperature of the nugget zone which further effect microstructure evolution and mechanical properties of the weld. Dinaharan et al.  reported that tool rotational speed was a significant FSW parameter. Khodir and Shibayanagi  revealed that the grain size decreases with increasing welding speed. Grain size decreases due to the lower temperature caused by the lower heat input associated with faster welding speed. Sharma et al.  evaluated that at low welding speed, weld nugget was more homogeneous because high heat input per unit weld length resulted in more homogeneous temperaturedistribution and effective recrystallization. Palanivel et al.  studied that frictionstir welding at higher welding speeds resulted in a shorter exposure time in the weld area with insufficient heat and poor plastic flow of the metal and caused some voids like defects in the joint. Ilangovan et al.  investigated that each pin profile had its own material flow characteristics like higher mixing of materials, reduction of TMAZ, HAZ regions. The joining of the materials of the weld interface is achieved by the frictional heat generated between the tool and the work-piece and the material flow.
The aluminium 6063 is welded by frictionstir welding process. The material has good surface which required less machining work over the surface for FSW. The tool preparation required a meticulous treatment of the tool is machined to the design. The tool shoulder and pin diameter is important which are designed through reference from journals and standards. The heat treatment is done at 960 0 c for 8hours a day and for good properties such as wear resistance and hardness. The sample 4 has high corrosion resistance than the other samples. The tool rotation and the transverse speed enhance material hardness and the tensile strength. The experimentation with various parameters are done in as-welded condition. The processed material are tested under different conditions of rotational speed and transverse speed(450,560,710) rpm with 20 mm/min and 40 mm/min. The tensile strength of the processed material specimen 560 rpm an 40mm/min has 159.66N/mm 2 wherein the base metal had 210 N/mm 2 . The tensile strength enhances the corrosion property in the FS Welded condition which retained 75% of the strength from the base metal. The hardness of the specimen is 45 HRB wherein the base metal has 52 HRB. The hardness increase is due to change in grain structure and it can be seen in microstructure. The hardness enhances the tensile property and corrosion property wherein the grain is closely packed as face centred cubic structure. The microstructure of the specimen 560 rpm and 40mm/min can be seen clearly. The grain size of the specimen is 13 micrometer wherein base metal13.5 micrometer. The corrosion test are carried out for the specimens. The test revealed a small weight loss in 25days. The rust is formed with white sedimentation after 6days. The corrosion starts after 6 th day and the corrosion rate is accelerated to more exposure. The metal is coated first with salt solution. The White and red rust is formed and there is weight loss in the metal. There is gradual increase in loss of weight up-to a point there after the metal is stabilised and corrosion stops. The optimal value
realized scientific studies and suggested the use of this welding method as a commercial process. He has successfully done a welding process between two metal rods and patented this process in 1956. Vill and his colleagues have further investigated the process with a number of studies. Researchers of American Machine and Foundry Corporation named Holland and Cheng have worked on thermal and parametrical analysis of friction welding. By the way, the first studies of friction welding in England were carried out by the Welding Institute in 1961. By modifying the friction welding, the Caterpillar Tractor Co. in the USA developed the method of inertia welding in 1962. Afterthis study, conventional friction welding has been regarded as the Russian type process and inertia welding asthe Caterpillar type process. With these advances, applications of friction welding have found several applications throughout the world. Friction welding is one of the most widely used welding methods in the industry after electron beam welding.
The Invention of frictionstir welding is done at UK welding institute in 1991 and the process is solid state metal joining permanent process. FrictionStir welding is a new solid – state joining method offering several advantages over conventional welding methods, including better mechanical properties, low residual stress and reduced occurrence of defects. A rotating tool consisting of a shoulder and a probe is plunged into the joint and traversed along the joint line to form a weld. Fig-1 shows the schematic diagram of FSW. A typical frictionstir weld consists of a thermo-mechanically effected zone which includes dynamically re-crystallized zone and the extensively deformed but not re-crystallized surrounding region, the heat affected zone and the unaffected base material AL6061&AL5083. The Process deals with two dissimilar metals. There is a significance to choose these materials as they are easily weldable,
The effect of tool pin pro file on the mechanical properties of the FSW joint scan be in ferred from Table1.The jointwelded by square pin profiled tool exhibits high tensile strength when com-pared to other joints. The joint fabricated by tapered square pin profiled tool has the least tensile strength. The tensile strength of joints, welded using hexagon, tapered hexagon, octagon and tapered octagon pin profiled tools do not change significantly. It is due to the difference in dynamic orbit created by the eccentricity of the rotating tool of the FSW process . The relationship be-tween the static volume and dynamic volume decides the path for the flow of plasticized material from the leading edge to the trailing edge of the rotating tool. This ratio is equal to 1.56 for square, 1.21 for pentagon and 1.11 for tapered pentagon pin profiles. In addition, those pin profiles produce a pulsating stirring action in the flowing material due to flat faces. The square
Frictionstir welding (FSW) is a solid-state welding process in which the relative motion between the welding tool and the work pieces produces heat. This makes the material soft, and therefore it can be joined by plastic deformation and diffusion. This method relies on the direct conversion of mechanical energy to thermal energy forming the weld joint without any external source of heat. In the FSW process, a non-consumable rotating tool is forced down into the joint line under conditions where the frictional heating is sufficient to raise the temperature of the work pieces. It can plastically deform and locally plasticize.
of aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft than commercial or military aircraft. Aluminium 6061 alloy generally present low weldability by traditional fusion welding process. The development of FrictionStir Welding (FSW) has provided an alternative improved way of satisfactorily producing weld joint in aluminium 6061 alloy. In FSW, the welding tool motion induces frictional heating and severe plastic deformation and metal joining process is done in solid state results, which results in defect free welds with good mechanical properties in aluminium alloy 6061. Unlike in traditional fusion welding, frictionstir welds will not encounter problems like porosity alloy segregation and hot cracking, and welds are produced with good surface finish. In this paper, an attempt was made to investigate the impact of process parameters of FSW in the mechanical properties of the joint. The tensile properties, microstructure, hardness of the FSW joints were investigated in the weldment and heat affected zone. The changes of mechanical properties are compared with the parental metal. The welding parameters such as tool rotational speed and welding speed plays a major role in deciding the joint characteristics. This paper focusses on optimization of all these parameters. From this investigation it was found that the joint made from the FSW yielded superior tensile properties and impact strength due to the higher hardness and fine microstructure.
is the unstable nature of the hole drilled in the liquid pool. Other observations (Katayama et al. 2010; Seto et al. 2000; Menga et al. 2014) support this hypothesis, and it has been reported that keyhole instability is the main cause of bubble initiation especially in deep penetra- tion welding. Katayama et al. (2010) present a mechanism of porosity formation during pulsed laser welding. Seto et al. (2000) report the same information for continuous laser welding. For pulsed laser welding, it is reported that when the laser is terminated, the melt surrounding the upper part of the keyhole flows downward to fill the keyhole. Porosity is formed when the upper part of the melt rapidly solidifies, preventing the melt from flowing down to fill the keyhole. With continuous laser welding, bubbles are formed at the bottom tip of the keyhole. Some of these bubbles are able to escape the molten pool, but others are trapped at the solidifying front, resulting in the formation of porosity at the bottom of the weld seam. At low welding speeds, porosity is formed from bubbles generated at the tip of the keyhole; whereas, at high laser-power densities, porosity is formed in the middle part of the keyhole (Katayama et al. 2010). Matsunawa et al. (2000) also reported that fluctuations of the keyhole resulted in the for- mation of bubbles at the tip of the keyhole, which in turn formed porosities. Hydrogen porosity can be ef- fectively reduced by increasing the welding speed so that insufficient time is available for the hydrogen to accumulate because of the rapid cooling and solidification. Using a high-power fibre laser, Katayama et al. (2009) investigated penetration and defect formation in several aluminiumalloys. They found that 10-mm thick plates of AA5083 were penetrated completely with a power density of 64 MW/cm 2
The quality of frictionstir processed (FSP) zone is controlled by the welding parameters of rotational speed, welding speed, and axial force. The optimization of all these parameters is very essential to obtain defect free joints. The formation of defect free FSP zone is influenced by both welding speed and pin profile . The formation of defects and discontinuities are controlled by the parameters such as spindle speed, welding speed and axial force. These defects and discontinuities obviously influence the tensile properties of the FSW joints. The wear rate decreases as axial force increases. Further increase in axial force leads to increased wear rate. The wear resistance follows an inverse trend of wear rate as estimated. Bonding occurs in FSW when a pair of surfaces is brought in the area of inter atomic forces. Adequate axial force exceeding the flow stress of material is required to make defect free joints. Axial force propels the plasticized material in the weld zone to complete the extrusion process. Axial force is also responsible for the plunge depth of the pin.
The fracture toughness of dissimilar aluminum alloys butt-joined by FrictionStir Welding (FSW) is studied. The aluminum grades used in this project were 5083 and 6061. The feasibility of using conventional belt-driven milling machine to perform FSW was also investigated by adding a custom-made compact clamping jig and FSW tool bit to the machine set up, and by varying machine parameters such as tool rotational speed (ɷ, rpm), tool traverse speed (v, mm/min), plunge depth (mm) and tool tilt angle. Preliminary FSW runs were done with the milling machine to modify it for the purpose of FSW. Two types of test were carried out which were tensile test and single edge notch tension (SENT) test. Both tests were performed on a Universal Testing Machine (UTM). By visual inspection, tunnel defect was seen in SENT specimens and in the dissimilar grade FSW joint for tensile testing specimen. The similar grade FSW joints performed less than their base material in terms of tensile strength. The critical stress intensity factor (SIF) for the welded specimens were found to be lower than critical SIF values known from literature for their respective materials.
Elrefaey et al.  were one of the first investigating the feasibility of lap joining of 2 mm-thick AA1100 H24 plates to 1 mm-thick copper plates. They found that the joint strength strongly depended on the penetration depth of the pin tip into the copper surface. The authors observed that the joints showed very weak fracture loads when the pin did not penetrate in the copper surface. On the other hand, slight penetration of the pin tip into the copper surfaceincreased the joint strength significantly. Although the level of bond strength was quite low, it exhibited a general tendency to increase with a rise in the rotation speed. Some years later, Abdollah-Zadeh et al.andSaeid et al in frictionstir lap welding of 4 mm-thick AA 1060 to 3 mm thick commercially pure copper, pointed out two factors affecting the welding results, i.e., the amount of brittle and hard intermetallic compounds and the “cold weld” condition. Whereas the welds produced under very high heat input conditions (high rotation speed and low traverse speed) presented formation of brittle intermetallic layers, in which strong micro-cracking takes place, the welds carried out under low heat input conditions (low rotation speedand high traverse speed) displayed incompletely welded interfaces.
Excellent properties are also found in fatigue. In another investigation, Abdollah-Zadeh et. al. studied microstructural and mechanical properties of Al/Cu lap joints. They observed a black area, which consists of intermetallic compounds of Al4Cu9, AlCu and Al2Cu near Al/Cu interface. The shear load decreased with increasing the rotational speed and decreasing welding speed. Low rotational speed resulted defective joints. Fonda et. al. investigated the microstructural evolution in FSW of 2195 Al–Li alloy. They observed large, undeformed grains far from the tool to the refined grains near the tool. It suggested that there was a single grain subdivision mechanism operating across all the regions around the tool. Simar et. al . studied the effect of the welding speed on the microstructure and mechanical properties of frictionstirweldedAlalloys. They found occurrence of dissolution of the precipitates and formation of coarse precipitates in HAZ. The strain hardening capacity of the WZ is larger than that of the HAZ. Giles et. al.  conducted frictionstir processing on AA2099 plate. They found equiaxed grains during FSP replacing elongated grains in conventional thermo mechanical processing. It leads to mechanical isotropy. FSP alters failure modes, especially in anticlastic bending.
The hardness of the parent metal was found to 68.6 hv.The weld parameters 1200 rpm, 120 mm/min, 12 kN had higher hardness value 77.6 hv .The hardness along the vertical direction increased from top to bottom towards stir zone and then decreased at the parent metal. The elongated and deformed grains were observed in the TMAZ region. This may be due to insufficient deformation strain and thermal exposure of this region. This region is located 3 to 4 mm away from the weld center, where the hardness is low
An example of 7075 alloy shows that it is heated to 4800C and the temperature is instantly decreased by keeping it in water called quenching. The alloy is very appropriate at this temperature to undergo different processes. Once this alloy is kept at a higher temperature than room temperature, the alloy strength increases with decreased ductility. Precipitate formation begins as it is kept at a super saturated level . Alloy has higher strength, lower density, greater toughness and lighter weight along with corrosion resistant properties. Their application in automotive, aviation, structures and models has been prominent. . Al and its alloys are used in the form of cast and wrought. This alloy is 3rd still used in its iron and steel application . This material's ability to display the property of light weight and high strength compared to other Alalloys makes it a sought-after material for applications in airframes and high stress components . The aluminum's reaction capacity depends on its ability to form an oxide layer to display the corrosion's positive effects. The decrease in resistance to corrosion depends on the percentage of the alloying element in it. Often there may be some solid precipitations or phases that interfere with the continuity of the developed oxide layer and significantly affect the matrix . The method adopted to change the state of metal specimen's with respect to its structure of metallurgy, mechanical properties and variations in stress is considered as heat treatment. The alloys are classified into two subgroups; heat-treatable alloys and alloys that non heat- treated. Aluminum alloy heat treatment falls under the category of heat treatable alloys that improves the materials hardness and strength. Alloys whose properties must be altered by cooling is classified as non-heat treatable alloys. Solutionizing, quenching and ageing are the main steps taken in the heat treatment process. Solution heat treatment is heating the alloy close to its eutectic temperature and keeping it for a specified long time to form a solid solution at that temperature. After solution heat treatment, quenching is followed to maintain the system in a super-saturated state . The strength of the formed alloy also increases as the temperature increases. In some specimens that have the eutectic phase if the temperature rises above the required eutectic temperature than the results will affect this phase's ______________________________
Images of the spot weld microstructure of all variants show a significant fragmentation of the grains within the structure of the weld in regards to the parent material (Fig. 5). Grain fragmentation within the structure of spot weld is a positive phe- nomenon from the point of view of material strength. However, the variants with a welding time of 1.5 s and 2 s (Fig. 6.) a boundary between sheet and tool penetration zone can be observed and it is a structural notch. A thermomechanical processing occurs in the penetration area of the tool, and more precisely the sleeve, in the mate- rial, this area is narrowed to the diameter of the tool (4.5 mm from axis of the weld) as a result. In this area, a significant grain fragmentation of the material can be observed. 4.5 mm from the axis of the joint, there is an evident boundary be- tween aforementioned areas. Beyond this border, the structure of the material gradually shifts from having small grains to grains the size of the parent material, and this is still a zone of thermomechan- ical processing. The visible boundary between the areas of the spot weld signify that there is a weak point in the structure, which is an undesir-
ABSTRACT: An experimentalinvestigation has been carried out, in present paper, on microstructure, Hardness and Tensile strength of weld butt joints of AA 6082. Two different welding processes have been considered: a conventional tungsten inert gas (TIG) process and an innovative solid state welding process known as frictionstir welding (FSW).which the relative motion between the tool and the work piece produces heat which makes the material of the two edges being joined plastic atomic diffusion. Tungsten inert gas welding process that uses the heat produced by an electric arc created between non consumable tungsten electrode and the weld pool. In this project an attempt is made to compare and investigate the process parameters of fsw and tig on the mechanical properties of the welds. The hardness, tensile strength is considered for investigation by tool speed, tool feed and maintaining constant depth of penetration of weld. The results indicate than the microstructure of fiction weld is different from the tungsten inert gas weldedjoint. The weld nugget consists of small grains in frictionstir welding and those are found in tungsten inert gas weld. The tensile strength of weld joint in frictionstir welding is more instead of tungsten inert gas Welding. Hardness test of frictionstir welding is more instead of tungsten inert gas where as in parent material also.
years old and the interest in it and its potential continues to increase dramatically. FSW can be applied to a multitude of products with varying material types and thicknesses. However, a continuous weld is not always required to meet the product performance requirements. Thus, one can consider some form of intermittent weld, such as FrictionStir Spot Welding. FrictionStir Spot Welding (FSSW) can be considered for many of the applications presently performed with traditional resistance spot welding (RSW), the basic concept of FSSW is remarkably simple. A non-consumable rotating tool with a specially designed pin and shoulder is inserted into the abutting edges of sheets or plates to be joined the tool serves two primary functions: (a) heating of work-piece, and (b) movement of material around pin to produce the joint. The heating is accomplished by friction between the tool and the work-piece and plastic deformation of work piece. The localized heating softens the material around the pin and combination of tool rotation and axial load. As a result of this process a joint is produced in ‘solid state’. From using this method to perform the Welding tests were performed using two welding parameters and the welds were sectioned and evaluated using optical microscopy. Mechanical testing of the spot joints was performed utilizing the tension-shear configuration. And also evaluate the hardness on the weld spot at the different zone nugget, TMAZ, HAZ and Base plate.