aluminum alloy sections. A huge increment in weldingspeed is achieved with high weld quality and superb joint properties. The impacts of weldingspeed on mechanicalproperties of the dissimilar joints are shown in Fig. 4-8. At the lowest (i.e. 40 and 63mm/min) and the highest (100mm/min) welding speeds, a lower tensile strength was noticed. The increment of weldingspeed prompts to the increment of the tensile strength up to the highest value, while additionally increase in weldingspeed effects in the decrease in the tensile strength of frictionstirwelded joints. The weldingspeed prompts the translation of tool, which thusly pushes the stirred material from front to the back of the tool pin and finishes the welding. The rubbing of tool shoulder and pin with the workpiece generates frictional heat. The weldingspeed determines the exposure time of this frictional heat per unit length of the weld and in this way influences the grain growth and precipitates. Optimum presentation time and translation of stirred material will lead to great consolidation of material with finer grains. Since joint which encounters such condition at the weldingspeed of 80 mm/min during welding displayed the highest UTS. The reduction in frictional heat production with an increase in weldingspeed was observed. Higher heat conditions prevail at lower welding speeds with slower cooling rate, which leads to coarsening of grains and dissolution of precipitates [10,18] Lower welding speeds cause uncalled for solidification of material, which leads to the reduction in UTS attributable to the defect. The mixing gets to be distinctly lacking at higher welding speeds. The material present on the advancing side of the tool does not travel enough to the retreating side, which causes a defect. Lower heat production with rapid cooling rate happens at higher welding speeds. The inclination of the tool to drag at higher welding speeds furthermore adds to the lower UTS. The weldingspeed impacts the plastic stream of material, change in grain size and precipitates and development of defects. The components that find the tensile strength of dissimilaraluminum alloy joints are the existence of macroscopic defects in weld zone and the level of plastic flow and amount of stirring of both the materials.
In the present experimental study, dissimilaraluminum alloy AA5083 and AA6082 were frictionstirwelded by varying tool shape, weldingspeed and rotary speed of the tool in order to investigate the effect of varying tool shape and welding parameters on the mechanicalproperties as well as microstructure. The frictionstirwelding (FSW) process parameters have great influence on heat input per unit length of weld. The outcomes of experimental study prove that mechanicalproperties increases with decreasing weldingspeed. Furthermore mechanicalproperties were also found to improve as the rotary speed increases and the same phenomenon was found to happen while using straight cylindrical threaded pin profile tool. The microstructure of the dissimilar joints revealed that at low welding speeds, the improved material mixing was observed. The similar phenomenon was found to happen at higher rotational speeds using straight cylindrical threaded tool.
Dissimilaraluminumalloys AA2024-T365 and AA5083-H111 were welded by frictionstir process. Welding parameters such as tool rotational speed (900, 1120 and 1400 rpm), weld speeds (16, 40 and 80 mm/min) and tool pin pro- files (square, triangular and stepped) were used to weld many joints to study their effect on the mechanicalproperties of the joint. Also, different locations of the material were studied as other parameter. The mechanicalproperties were evaluated using tensile and hardness tests. The microstructure characte- rization of the processed alloys was carried out using optical microscopy. Ma- cro and microstructures of parent and welded specimens indicated that the weld parameters have a significant effect on mechanical and microstructural properties of the welds. However, defect-free as well as higher strength was obtained at higher speed of 80 mm/min.
plunge depth of 0.2 mm were applied to the tool. Figure 1 shows a schematic illustration of frictionstirwelding process between AA6061-T6 and Ti-6Al-4V alloy. During FSW, advancing side is aluminum alloy and retreating side is titanium alloy. Contrary to conventional frictionstir butt welding, the tool probe center was nearly shifted by the probe radius towards the aluminum plate. Therefore, except for a few tenth miilimerter, the stirring action of the probe occured on the aluminum plate of the joint. This was conducted to prevent probe wear and over heating of the aluminum alloy. This welding process was similar to the FSW of steel- aluminum joints. Figure 2 shows a schematic illustration of joint interface. To evaluate interfacial microstructure and mechanicalproperties in accordance with the probe position, probe positions were varied along thickness direction of base metals. Probe root area was equivalent to the weld surface and the probe was completely inserted in titanium alloy of this region. However, probe tip area was equivalent to to the weld bottom and the probe was not contact to taitanium alloy. Interfacial microstructure was inspected by optical microsco- py (NIKON, EPIHOT200), scanning electron microscopy (JEOL, JSM-700F) and scanning transmission electron mi- croscopy (FEI, TECNAI); sections taken perpendicular to the welding direction were polished and etched (keller’s reagent) by using conventional methods. TEM specimens on a cross- section perpendicular to welding direction were fabricated by focused ion beam (FEI, QUANTA3D). The bright ﬁeld images of the weld interface were observed. The high angle annular dark ﬁeld (HAADF) images were observed and consequently elements mapping was carried for the same ﬁeld. Tensile test was carried out by using an instron-type tester under a cross head speed of 1:7 10 5 m/s at room temperature. Tensile test specimens (gage length: 45 mm, width: 7.5 mm) were machined perpendicular to the welding direction from joint. After tensile test, fracture surfaces were inspected by a scanning electron microscopy equipped with X-ray spectroscopy analysis system (EDX). Vickers hardness
However, the dissimilar FSW involved with UFGed materials has never been reported according to the best of our knowledge. The FSW of dissimilaralloys has been significantly studied including dissimilaraluminumalloys, Al/Mg alloys, Al/Steel pairs, etc. The main salient feature of FSW of dissimilar metals 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 aluminumalloys 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-T6aluminumalloys. 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-T6aluminumalloys [ 24 ]. However, the UFGed materials have not been reported to be dissimilar FSW processed with other materials.
Although there are numerous reports on frictionstirwelding of 6000 series Al-alloy plates, most of these works concentrated on the determination and the effect of welding parameters on microstructural and mechanical characterization of the joints produced[16-19]. This implies that the different FSW process parameters of the welds lead to different material flow behavior such as rotational speed and traverse speed, thus influencing the microstructures and mechanicalproperties of the joint [20-22]. Therefore, there is still a need for further research on frictionstirwelding of AA6061 Al-alloy plates, particularly for works aiming at the determination of the ways to improve mechanicalproperties of the joints regardless of welding parameters. In this paper, AA 6061-T6 Al-Alloy plates were joined by frictionstirwelding using constant sets of weld parameters in 5 different temperatures. The correlation between preheating and mechanicalproperties on similar frictionstir butt welded joints of aluminum alloy plates were investigated. The novelty of this work is employing the preheating for similar joint of aluminum sheets.
The higher hardness measured in the TMAZ especially for 7075 al alloy side could be attributed to both higher dislocation density and precipitates introduced during cool- ing. The minimum hardness values in the HAZs for two alloys indicate that overaging process occurred in these regions. The slight increase of hardness in HAZ with increasing rotation speed could be attributed to the relatively increasing of heating or cooling rates during welding by increasing rotation speeds. Increasing heating rate reduce the time for precipitates to grow and hence leads to hardness increase in HAZ. Also, increasing cooling rate after welding increases the amount of supersaturated solute which will be available for further precipitation reaction at room temper- ature. Although, there are some previous works 22–24) dealing
process. In particular, it can be used to join high-strength aerospace aluminum and other metallic alloys that are hard to weld by conventional fusion welding. It was performed on 4mm thickness Al6061 and Al5083 dissimilarAluminumalloys. Aluminum alloy light weight, softer, tendency to bend easily, cost effective in terms of energy requirements so aluminum alloy has selected in this FSW technique. In this welding when two metals are joined with the help of heat generated by rubbing metals against each other. The frictionstirwelding is mostly used for joining aluminumalloys. The main defects occurring in this welding are holes, material flow rate. These defects are mainly caused due to improper selection of welding parameters. In this project the mechanicalproperties of FSW dissimilaraluminum alloy Al5083 and Al6061 has tested with the help of universal testing machine, hardness testing by Vickers hardness at various zones of the welded joints. In this experimental the testing of mechanicalproperties based on the input parameters such as rotational speed, weldingspeed and offset angle with proper welding parameters. Finally, the experimental results will be compared with microstructures are analyzed by optical microscope.
The main objective of this research is to conduct an investigation into the effect of welding parameters on the microstructural and mechanicalproperties of frictionstir (FS) welded butt joints of dissimilaraluminum alloy AA6061 and AA7075. Frictionstirwelding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. This will be used to join aerospace aluminumalloys and other metallic alloys that are hard to weld by conventional fusion welding. In this process, two metal pieces, AA6061 and AA7075, 100 x 50 x 6mm thick, are welded under different welding parameters like tool rotation speed and transverse feed. The effects of welding parameters were evaluated by studying the resulting mechanicalproperties such as hardness distribution and tensile properties for axial welded zone.
N. T. Kumbhar et. al. 2008 managed FrictionStirWelding of Al 6061 Alloy. States that during the frictionstirwelding, high deformation is observed at the nugget zone and the developed microstructure strongly influences the mechanicalproperties of the joint. FSW trials were done utilizing a vertical milling machine on Al 6061 alloy. Morteza Ghaffarpour, et. al. 2013 In his Review of Dissimilar Welds of 5083-H12 and 6061-T6 performed by FrictionStirWelding, describes that as the conventional fusion welding is undesirable for weldingaluminumalloys, there are numerous works performed on the aluminumalloys by FSW. These works are considering to the effects of FSW parameters on sheet formability, weld quality after FSW, and optimization of the FSW process. S. Jannet et. al. 2013 managed Comparative research of frictionstirwelding and fusion welding of 6061-T6 and 5083-O aluminum alloy in view of microstructure and mechanicalproperties states. In this study, the mechanicalproperties of welded joints of 6061- T6 and 5083-O aluminum alloy determined utilizing frictionstirwelding (FSW) with four rotational speeds (450, 560, 710 and 900 rpm) and conventional fusion welding are investigated.
Abstract: Frictionstirwelding (FSW) of AA6061-T6aluminum alloy has been attempted to overcome limitations of fusion welding of the same. The FSW tool, by not being consumed, produces a joint with predominant advantages of high joint strength, lower distortion and absence of metallurgical defects. Process parameters such as tool rotational speed, tool traverse speed and axial force and tool dimensions play an important role in obtaining a specific temperature distribution and subsequent viscosity distribution within the material being welded; the former controlling the mechanicalproperties and later the flow stresses within the material in turn. A software based study to find effect of tool dimensions on the peak temperatures generation during FSW for the said aluminum alloy was carried out to explore the capabilities of the same and provide basis for further research work related to the different aluminumalloys.
 E. Salari, M. Jahazi, A. Khodabandeh, and H. Ghasemi- Nanesa, “Influence of tool geometry and rotational speed on mechanicalproperties and defect formation in frictionstir lap welded 5456 aluminum alloy sheets,” Mater. Des., vol. 58, pp. 381–389, 2014.  B. Parida and S. Pal, “Fuzzy assisted grey Taguchi approach for optimisation of multiple weld quality properties in frictionstirwelding process,” Sci. Technol. Weld. Join., vol. 20, no. 1, pp. 35–41, 2014.  R. K. Kesharwani, S. K. Panda, and S. K. Pal, “Multi
Ouyang et al.  studied the microstructural evolution during frictionstir butt welding of AA6061-T6 to copper, in which the latter was placed on the advancing side (AS). As a general note, they claimed that FSW of aluminium to cop- per was difficult due to the formation of brittle intermetallic compounds (IMCs) which led to poor mechanicalproperties. In their studies  , the dissimilar mechanically mixed zone i.e. stir zone and thermo-mechanically affected zone (TMAZ) exhibited a complex microstructure with several IMCs such as Al2Cu, CuAl and Al4Cu9. However distinctive microhard- ness levels were observed at the stir zone, and there was a lack of further investigation on the joint mechanical prop- erties. Abdollah-Zadeh et al.  studied the effect of tool rotational speed and tool traverse speed on the microstructure and mechanicalproperties of the joint by only considering the lap configuration. The existence of Al2Cu, CuAl and Al4Cu9 IMCs was also confirmed as in the aforementioned study  . The study  concluded that a suitable rotational to traverse speed ratio resulted in maximising the joint mechanical prop- erties. Furthermore, the relationship between IMC formation and joint mechanical strength has been investigated by Xue et al.  at different tool offsets, tool rotational and traverse speeds of dissimilar AA1060 aluminium to pure copper joints. Noticeable improvements in the ultimate tensile strength (UTS) were observed when the IMC thickness increased, espe- cially at the interface between the aluminium base metal and the stir zone. Their findings  were in agreement with other studies [21–24] , whereas other published work [25,26] proposed that the joint mechanical strength depended on the volume fraction, geometry and distribution of the IMCs.
The butt joints of semi solid metal 6061 were produced in as cast conditions by frictionstirwelding process (FSW). This experiment studied in pre/post heat treatment (T6) using the weldingspeed 160 mm / min with tilt angle tool at 3 degree and straight cylindrical tool pin. The factors of welding were rotating speed rates at 710, 1000, 1400 rpm and heat treatment conditions. They were divided into (1) As welded (AW) joints, (2) T6 Weld (TW) joints, (3) Weld T6 (WT) joints, (4) T6 Weld T6 (TWT) joints, (5) Solution treated Weld Artificially aged (SWA) joints and (6) Weld Artificially aged (WA) joints. Rotating speed and heat treatment (T6) condition were an important factor to micro, macro structure of metal and mechanicalproperties of the weld. Increasing rotating speed and different heat treatment condition impacted onto tensile strength due to the defects on joints. Therefore the optimum welding parameter on joint was a rotating speed 1400 rpm, the weldingspeed 160 mm/min, heat treatment condition of Solution treated Weld Artificially aged (SWA) which obtained the highest tensile strength 179.80 MPa, as well as, the maximum average hardness of 92.7 HV at tool rotation speed 1400 rpm, weldingspeed 160 mm/min, heat treatment condition of Weld T6 (WT).
In the as-welded condition, the relation between different welding speeds and hardness in the weldment is summarized in Fig.7a. It indicates the cross-sectional hardness profile from retrieving side metal through centre of the weld to advancing metal. Hardness of the stir zone was lower than both the base metals (AA2024 and AA6351). In a precipitation hardened Al alloy, the mechanicalproperties of the weld zone mainly depended on the precipitates behavior during the welding thermal cycles. This result could be attributed to the reason why lower hardness than that of base metals. Hardness of the stir zone showed more scattered values at higher weldingspeed (1.2mm/sec). A higher weldingspeed resulted in less homogeneously dispersed Mg 2 si and Al2CuMg particles. Therefore, larger
number of pass in FSP found to improve the distribution of particles in the stir zone. Byung-wook et al.  reported that AA5083-H32 aluminium alloy composite fabricated with SiC particles of mean diameter 4µm, which were inserted in to the groove of size 2mm in width and 1mm in depth. The particle distribution in the stir zone was found to be uniform after two passes with refinement in the grain size due to pinning effect, which improved the microhardness of the composite. In the works of Don- Hyun CHOI et al. , the SiC particles were inserted in to the metal matrix of AA6061-T4 aluminium alloy. During FSP these particles were deposited in to the groove of size 2mm in width and 1mm in depth, which yielded grain refinement due to uniform distribution of SiC particles and improved the microhardness of the composite by 80HV. Dolatkhah et al.  investigated the FSP of AA5052 composites produced by micro and nanoparticles. The SiC particles with average mean diameter of 50nm and 5µm were inserted in to the groove of size 2mm in width and 1mm in depth, to produce the composites. The nanocomposite exhibited improved hardness and wear properties with the increase in the number of passes and by changing of tool rotational direction between the passes. Izadi et al.  studied the multi-pass FSP of AA5059 alloy by inserting the carbon nanotubes of mean diameter 30-50nm in to the groove of size 2.5mm in width and 1.8mm in depth. After three passes the reinforcements were distributed uniformly in the stir zone of the nanocomposite which restricted the grain size and yielded higher microhardness. Morisada et al.  reported the fabrication of AZ31 surface composites by Multi-walled carbon nanotube reinforcements having an outer diameter of 20-50nm. The reinforcements were inserted into a groove of 1 mm in width and 2 mm in depth. It has been shown that the carbon nanotube reinforcements restrict the grain size, and the composite exhibited improved microhardness. Morisada et al.  also investigated AA5083 composites fabricated by fullerene powder of mean grain size 25.4 µm in to a groove of size 1 mm in width and 2 mm in depth during frictionstir processing. Abnar et al.  studied the frictionstirwelding of AA3003-H18 aluminium alloy by depositing the reinforcements in the stir zone. He reported that Cu and premixed Al-Cu powder were inserted between the two
Rolled plates of AA6061-T6 and AA7075-T6 of 5mm thickness were considered for butt configuration. Each plates of size 150 x75 x 5mm were prepared by using power hacksaw and milling. The welding was performed normal to the rolling direction. AA6061-T6 was placed in the advancing side and AA7075-T6 was placed in the retreating side (Guo, et al., 2014). The chemical composition and the mechanicalproperties of the base materials are shown in the Tables 1 and 2. The parameters considered for the study include Tool rotational speed (N), Weldingspeed (S), Axial Load (L), and shoulder diameter (D). The ranges of the parameters are found by number of trial run and identified for the major defects using macroscopic investigation. The various parameters and their corresponding ranges are shown in the Table 3. Five tool rotational speed, three weldingspeed, axial speed and Shoulder diameter to fabricate the joints. A computer numerical control FSW machine was used to produce the joints. The tensile specimen was prepared as per the ASTM E8M-09 guidelines (ASTM E8 M-09, 2009) and the dimensions are shown in the Fig.1. A servo controlled universal testing machine was used to find the tensile strength, From each joint three tensile specimens were prepared perpendicular to the welding direction and the average of the same was recorded. For the metallographic examination the specimen was prepared to the required size from the joint which comprises the stir zone, thermo mechanically affected zone heat affected zone and the base metal.
expulsion of material on the top surface leaving a ribbon like effect which occurs due to excessive forge load or an excessively hot weld. Other defects that occur in the FSW process are burr and surface galling that can be seen in most of the samples. These defects resulted from the metal sticking to the pin tool and from excessively hot welds. Some severe defects occurring in the FSW specimens can cause degradation of its mechanicalproperties . The weld appearance is affected by the heat input being supplied by the tool rotational speed during FSW jointing. In Figure 3(F), the defect shown is surface galling which is due to the material sticking to the tool pin and the low travelling speed. These defects can reduce the strength of the welded joints and can be prevented by increasing the axial force pressure and increasing the rotational speed so that the stirring action between materials will smooth the formation of the flow arm at the weld line .
The aim of this work was to gain basic knowledge on the corrosion behavior of dissimilar 2024A/6056 joints produced by frictionstirwelding (FSW). Because of the complexity of the corrosion mechanisms induced by the galvanic coupling between both alloys, the corrosion behavior of similar frictionstir welds made from the correspondent base metals was also investigated to provide a basis for the understanding of dissimilar joints. Simultaneous action of mechanical loading and corrosive attack can further deteriorate the performance of the joints thus compromising their safe operation in service applications. Therefore, the resistance to stress corrosion cracking (SCC) and the residual fatigue life of pre-corroded dissimilar FSW coupons were also studied. Moreover, in an effort to obtain better mechanical and corrosion performances, the effect of a post weld heat treatment was evaluated. The similar and dissimilar joints investigated in this study were produced by FSW using 4 mm thick sheets of the aluminumalloys 2024, 2024A and 6056. To create the post-weld heat treated condition the FSW 2024-T3, 6056-T4 and 2024A-T3/6056-T4 as welded joints were artificially aged at 190 °C for 10 h. This heat treatment resulted in a T8 temper for the 2XXX base materials, while the 6056 alloy exhibited a small degree of overaging, but still remained close to the T6 temper.
Abstract : The advancement of the FrictionStirWelding has given another improved method to creating aluminum joints, in a speedier and solid way. In present investigation the impacts of welding process parameters on the Vickers micro hardness of dissimilaraluminum alloy (AA5083 - AA6061) joints created by FrictionStirWelding is analyzed. Tool rotational speed, weldingspeed and tool tilt angle have been taken as process parameters. Taguchi Design of Experiment (DOE), Analysis of variance (ANOVA) and main effect plot were utilized to calculate the significant parameters and set the optimal level for every parameter. Confirmation trials were performed on the optimum level. As indicated by the ANOVA results, the most critical contributing factors for Vickers micro hardness was determined as Tool rotational speed (1120rpm) and weldingspeed (70 mm/min) and tool tilt angle (2 0 degrees). Vickers micro hardness tests were performed keeping in mind the end goal to describe the hardness in the region of the weld affected area. The predicted optimal value of hardness of frictionstirweldeddissimilarAA5083 and AA6061alloys is 94.8 VHN. The outcomes were confirmed by further trials.