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Cross section of the macrograph (a), SEM micrograph of grains and distribution of intermetallic particles in FSLW 1 (b) top (c) bottom and FSLW 2 (d) top (e) bottom.
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The corrosion behavior at different positions (top and bottom) of the weld nugget zone along the thickness plates in AA6061-T6 aluminum alloys welded by friction stir lap welding, under the conditions of 1000 rpm-60 mm/min and 900 rpm-40 mm/min in a 3.5 wt% NaCl solution, was investigated by Tafel polarization at ambient temperature. The morphology...
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... friction-stir lap welding (FSLW) process and joint design used in this research are depicted in the schematic in Figure 1. As shown in Figure 1, the dimensions of each overlapping plate were up to 220 mm in length and 140 mm in width, allowing them to be longitudinally overlap welded parallel to the plate's rolling direction using an automatic CNC machine. The overlap along the linear direction of the plate was 50 mm wide. A welding fixture was designed to tightly clamp the lapped parent alloy to be welded on the worktable. A supporting plate of identical thickness was placed underneath the upper plate to help align and stabilize the plates to be welded. A single FSLW pass was performed along the longitudinal centerline of the overlap. The chosen tool parameters used for welding in this work are given in Table 2, and the welding conditions are listed in Table 3. To improve the weld joining, the tool was tilted 3 degrees from the plate's normal direction toward the trailing side of the tool during welding. Additionally, a clockwise rotational direction was ...
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... friction-stir lap welding (FSLW) process and joint design used in this research are depicted in the schematic in Figure 1. As shown in Figure 1, the dimensions of each overlapping plate were up to 220 mm in length and 140 mm in width, allowing them to be longitudinally overlap welded parallel to the plate's rolling direction using an automatic CNC machine. The overlap along the linear direction of the plate was 50 mm wide. A welding fixture was designed to tightly clamp the lapped parent alloy to be welded on the worktable. A supporting plate of identical thickness was placed underneath the upper plate to help align and stabilize the plates to be welded. A single FSLW pass was performed along the longitudinal centerline of the overlap. The chosen tool parameters used for welding in this work are given in Table 2, and the welding conditions are listed in Table 3. To improve the weld joining, the tool was tilted 3 degrees from the plate's normal direction toward the trailing side of the tool during welding. Additionally, a clockwise rotational direction was ...
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... compare the corrosion behavior of the test samples, Tafel polarization curves were plotted using a PARSTAT 2273 equipped with the Power Suite software according to the ASM standard 15 in a 3.5 wt% aerated NaCl aqueous solution (pH = 5.5) at ambient temperature. Prior to placing the test samples in the open glass vessel containing the test solution for use as a corrosion cell, they were embedded in cold-setting resins in order to expose only a single surface to the test solution, and these were connected electrically with a copper wire after being set in a polyethylene tube. Immediately prior to each experiment, the surface of the sample was dipped in concentrated HNO 3 for 30 s. The electrochemical measurement consisted of a standard three electrode setup with the sample as the working electrode, including both the top and bottom regions of the nugget (0.3 cm 2 ), a saturated calomel electrode SCE (0.242 V vs. SHE) as the reference electrode, and a graphite rod as the counter electrode. The Tafel polarization curves were recorded in the potential range of -0.25 mV to +0.75 mV with respect to the OCP at a scan rate of 1 mVs -1 after allowing a steady-state potential to develop for 30 min. The corrosion potentials (E corr ) and corrosion current densities (I corr ) were calculated using Tafel extrapolation methods. All the experiments in this study were repeated at least twice to ensure reproducibility. Figure 1 depicts the backscattered electron micrographs of the grains and distribution of intermetallic particles at different WNZ positions for FSLW 1 as 1000 rpm-60 mm/min and FSLW 2 as 900 rpm-40 mm/min. The EDS analyses of the intermetallic particles are summarized in Table 3. Two types of intermetallic particles, including the Fe-rich and the Si-rich particles are observed as transparent and dark particles, respectively. Indeed, for FSW under different values of ω (rpm) and ʋ (mm/min), the temperature and material flow patterns have been studied by numerous researchers. Fratini and Buffa 16 reported that with increasing ω (rpm) and decreasing ʋ (mm/min), the quality of the welding will be enhanced due to the increase in stirring effects. Furthermore, according to Arbegast and Hartley 17 , both the tool rotational speed (ω, rpm) and the welding speed (ʋ, mm/min) display a significant effect on the thermal input and mechanical properties. Ren et al. 18 demonstrated that it is difficult to quantitatively estimate the thermal input (Heat Index, HI) and mechanical properties due to the change in both rotation speed (ω) and welding speed (ʋ). Based on experimental thermal observation, a Heat Index (HI) parameter has been used to represent the thermal input during FSW, which is defined as [19][20][21] ...
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... the welding process, the electro spark wire- electrode cutting machine was used to remove sample cross sections from the welded plate's perpendicular to the welding direction for microstructural examination and corrosion studies. As a result, the samples were cut along the welding direction to separate the weld nugget zone (WNZ) from the welded joints. Then, the WNZ was sliced into two zones (top and bottom) along the thickness of the plates, as shown in Figure 1a. The samples were used in the flat configuration after careful preparation by applying Table 1. Nominal composition of parent alloy used in the welding test (in ...
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... to Figure 1, the average grain size in the bottom WNZ half of FSLW 1 and FSLW 2 is slightly larger than that in the top half, showing an indistinct recrystallized structure. It is apparent that, as shown in Figure 1, the sizes of the intermetallic particles in the bottom halves of the WNZ in FSLW 1 and FSLW 2 are larger than in the top halves, but the distribution of intermetallic particles in the top half of the WNZ is greater than that at the bottom for both welding conditions. This can be attributed to the generation of different heat profiles in the FSLW 1 and FSLW 2, showing microstructure inhomogeneity in the weld nugget zones. Due to the higher pressure on the upper plate, established as the result of friction in the upper plate shoulder rather than the bottom plate, the average grain size in the top half of the nugget was smaller than that in the bottom half for both welding conditions. In addition, Hariri et al. 22 proved that by increasing the (ω 2 /ʋ) ratio, the maximum friction heat generation (i.e., Heat index) in the WNZ increases, generating coarse recrystallized grains in the weld nugget zone. Therefore, the average grain size in the weld nugget zone of FSLW 2 was larger than that of FSLW 1. In this manner, it was also observed that the average grain size in the top half of the WNZ decreased compared to that of the bottom half in the FSLW 2 with respect to the FSLW 1. Furthermore, in the FSLW 1, as a result of the higher rotation speed, excess plastic flow material was created, resulting in turbulence arising in the plastic flow field. Thus, the average grain size decreased in the FSLW 1 rather than in the FSLW 2 for both halves of the weld nugget zones. It is clear that the plastic deformation was reduced along the thickness of plates. Therefore, the intermetallic particles in the top half of the WNZ experience greater mechanical stirring and crushing mechanics, resulting in smaller particles than in the bottom (Figure 1). Additionally, it can be seen from Figure 1 that for the FSLW 2, the intermetallic particles rich in Fe and Si underwent an abnormal growth because of the localized high temperature, and as a result, they were separately distributed in the Al matrix on the top and bottom of the weld nugget ...
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... to Figure 1, the average grain size in the bottom WNZ half of FSLW 1 and FSLW 2 is slightly larger than that in the top half, showing an indistinct recrystallized structure. It is apparent that, as shown in Figure 1, the sizes of the intermetallic particles in the bottom halves of the WNZ in FSLW 1 and FSLW 2 are larger than in the top halves, but the distribution of intermetallic particles in the top half of the WNZ is greater than that at the bottom for both welding conditions. This can be attributed to the generation of different heat profiles in the FSLW 1 and FSLW 2, showing microstructure inhomogeneity in the weld nugget zones. Due to the higher pressure on the upper plate, established as the result of friction in the upper plate shoulder rather than the bottom plate, the average grain size in the top half of the nugget was smaller than that in the bottom half for both welding conditions. In addition, Hariri et al. 22 proved that by increasing the (ω 2 /ʋ) ratio, the maximum friction heat generation (i.e., Heat index) in the WNZ increases, generating coarse recrystallized grains in the weld nugget zone. Therefore, the average grain size in the weld nugget zone of FSLW 2 was larger than that of FSLW 1. In this manner, it was also observed that the average grain size in the top half of the WNZ decreased compared to that of the bottom half in the FSLW 2 with respect to the FSLW 1. Furthermore, in the FSLW 1, as a result of the higher rotation speed, excess plastic flow material was created, resulting in turbulence arising in the plastic flow field. Thus, the average grain size decreased in the FSLW 1 rather than in the FSLW 2 for both halves of the weld nugget zones. It is clear that the plastic deformation was reduced along the thickness of plates. Therefore, the intermetallic particles in the top half of the WNZ experience greater mechanical stirring and crushing mechanics, resulting in smaller particles than in the bottom (Figure 1). Additionally, it can be seen from Figure 1 that for the FSLW 2, the intermetallic particles rich in Fe and Si underwent an abnormal growth because of the localized high temperature, and as a result, they were separately distributed in the Al matrix on the top and bottom of the weld nugget ...
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... to Figure 1, the average grain size in the bottom WNZ half of FSLW 1 and FSLW 2 is slightly larger than that in the top half, showing an indistinct recrystallized structure. It is apparent that, as shown in Figure 1, the sizes of the intermetallic particles in the bottom halves of the WNZ in FSLW 1 and FSLW 2 are larger than in the top halves, but the distribution of intermetallic particles in the top half of the WNZ is greater than that at the bottom for both welding conditions. This can be attributed to the generation of different heat profiles in the FSLW 1 and FSLW 2, showing microstructure inhomogeneity in the weld nugget zones. Due to the higher pressure on the upper plate, established as the result of friction in the upper plate shoulder rather than the bottom plate, the average grain size in the top half of the nugget was smaller than that in the bottom half for both welding conditions. In addition, Hariri et al. 22 proved that by increasing the (ω 2 /ʋ) ratio, the maximum friction heat generation (i.e., Heat index) in the WNZ increases, generating coarse recrystallized grains in the weld nugget zone. Therefore, the average grain size in the weld nugget zone of FSLW 2 was larger than that of FSLW 1. In this manner, it was also observed that the average grain size in the top half of the WNZ decreased compared to that of the bottom half in the FSLW 2 with respect to the FSLW 1. Furthermore, in the FSLW 1, as a result of the higher rotation speed, excess plastic flow material was created, resulting in turbulence arising in the plastic flow field. Thus, the average grain size decreased in the FSLW 1 rather than in the FSLW 2 for both halves of the weld nugget zones. It is clear that the plastic deformation was reduced along the thickness of plates. Therefore, the intermetallic particles in the top half of the WNZ experience greater mechanical stirring and crushing mechanics, resulting in smaller particles than in the bottom (Figure 1). Additionally, it can be seen from Figure 1 that for the FSLW 2, the intermetallic particles rich in Fe and Si underwent an abnormal growth because of the localized high temperature, and as a result, they were separately distributed in the Al matrix on the top and bottom of the weld nugget ...
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... to Figure 1, the average grain size in the bottom WNZ half of FSLW 1 and FSLW 2 is slightly larger than that in the top half, showing an indistinct recrystallized structure. It is apparent that, as shown in Figure 1, the sizes of the intermetallic particles in the bottom halves of the WNZ in FSLW 1 and FSLW 2 are larger than in the top halves, but the distribution of intermetallic particles in the top half of the WNZ is greater than that at the bottom for both welding conditions. This can be attributed to the generation of different heat profiles in the FSLW 1 and FSLW 2, showing microstructure inhomogeneity in the weld nugget zones. Due to the higher pressure on the upper plate, established as the result of friction in the upper plate shoulder rather than the bottom plate, the average grain size in the top half of the nugget was smaller than that in the bottom half for both welding conditions. In addition, Hariri et al. 22 proved that by increasing the (ω 2 /ʋ) ratio, the maximum friction heat generation (i.e., Heat index) in the WNZ increases, generating coarse recrystallized grains in the weld nugget zone. Therefore, the average grain size in the weld nugget zone of FSLW 2 was larger than that of FSLW 1. In this manner, it was also observed that the average grain size in the top half of the WNZ decreased compared to that of the bottom half in the FSLW 2 with respect to the FSLW 1. Furthermore, in the FSLW 1, as a result of the higher rotation speed, excess plastic flow material was created, resulting in turbulence arising in the plastic flow field. Thus, the average grain size decreased in the FSLW 1 rather than in the FSLW 2 for both halves of the weld nugget zones. It is clear that the plastic deformation was reduced along the thickness of plates. Therefore, the intermetallic particles in the top half of the WNZ experience greater mechanical stirring and crushing mechanics, resulting in smaller particles than in the bottom (Figure 1). Additionally, it can be seen from Figure 1 that for the FSLW 2, the intermetallic particles rich in Fe and Si underwent an abnormal growth because of the localized high temperature, and as a result, they were separately distributed in the Al matrix on the top and bottom of the weld nugget ...
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... is clear that both increasing ω and decreasing ʋ (increasing the (ω 2 /ʋ) ratio) result in an increase in the FSW Heat Index. Accordingly, and based on the principles of grain growth, the grain size of the structure is increased at faster ʋ (Figure 1). According to Table 2, the HI in the FSLW 2 is higher than that in the FSLW 1; thus, the average grain size in the WNZ of FSLW 1 is smaller than that of FSLW 2, resulting in FSLW1 having a finer grain structure than FSLW 2. Furthermore, the quantity of the coarse intermetallic particles and their distributions are promoted with the increased Heat Index (HI) in FSLW 2 rather than FSLW 1 (Figure ...
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... is clear that both increasing ω and decreasing ʋ (increasing the (ω 2 /ʋ) ratio) result in an increase in the FSW Heat Index. Accordingly, and based on the principles of grain growth, the grain size of the structure is increased at faster ʋ (Figure 1). According to Table 2, the HI in the FSLW 2 is higher than that in the FSLW 1; thus, the average grain size in the WNZ of FSLW 1 is smaller than that of FSLW 2, resulting in FSLW1 having a finer grain structure than FSLW 2. Furthermore, the quantity of the coarse intermetallic particles and their distributions are promoted with the increased Heat Index (HI) in FSLW 2 rather than FSLW 1 (Figure ...
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... some of the more complicated multi-pass processes compared to the FSW (e.g., equal channel angular pressing), the influence of texture variation (in addition to the grain size) on corrosion behavior should be considered 22,23 . However, during FSW, the extensive shear plastic deformation is the primary phenomenon, leading to a dynamic recrystallized fine grain microstructure in the WNZ 8,24 . Meanwhile, due to the rapid heat transfer and the reduction in plastic deformation along the thickness of the plates, the grain size in the top half of the WNZ is smaller than that in the bottom half for FSLW 1 and FSLW 2 (Figure ...
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... The results showed that most of the heat (around 96.84%) was produced from friction at the interface of the tool and workpiece. Matori et al. [11] investigated the corrosion properties of AA6061-T6 joint obtained using FSSW. The effect of pin length on the FSSW process for dissimilar aluminum and steel joints was studied by Piccini and Svoboda [12]. ...
In this investigation, the vibration of the workpiece is accompanied by the rotating movement of the tool during friction stir spot welding. The method is entitled to friction stir spot vibration welding (FSSVW). Al5083 alloy samples are joined by two welding methods, friction stir spot welding (FSSW), and FSSVW under different plunge depths (DP). The microstructures and fracture surface of the welded zones were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM), respectively. Analyzing the microstructures and mechanical properties of welded samples in both methods revealed that weld region grain size reduced and its hardness increased as the mechanical vibration and high plunge depth have been applied. In addition, the strength and ductility values of FSSV welded specimens with high plunge depth were higher than those produced by FSSW under low plunge depth. Furthermore, it was concluded that the effect of vibration on microstructure and mechanical properties of welded specimens increase as vibration frequency is increased.
... The generation of high heat input sensitizes the grain boundaries in the stirred zone as the FSP progresses. Pitting corrosion mainly occurs in the vicinity of the iron (Fe)-rich intermetallic particles as also discovered by Gharavia et al. in their study [17]. The X-ray diffraction (XRD) pattern of the reinforcement powder and that of the FSPed samples is shown in Fig. 8. ...
Aluminium alloys has been favoured in many applications because of its exciting properties which include light weight and corrosion resistance. However, susceptibility to pitting corrosion and intergranular corrosion (IGC) are some of the drawbacks of aluminium. The surface of aluminium can be modified to improve its corrosion resistance properties. Surface modification is a surface engineering process that is performed to alter the properties of material surface to improve its service life. Friction stir processing (FSP) is a relatively new and an important solid state material surface modification process. In this study, investigation on the influence of FSP processing parameters on the resulting corrosion resistance surface properties of pure commercial aluminium and Ni-40Fe-10Ti surface composite using friction stir processing technique was conducted. The processing parameters that were studied are tool rotational speed and transverse speed, while all other processing parameters were kept constant. The corrosion behaviour was studied using three-electrode electrochemical cell, and the microstructure of the corroded samples was studied using optical microscope (OM). The results showed that the addition of Ni, Fe and Ti caused a decrease in the anodic and cathodic current densities. The set of processing parameters that resulted in the lowest corrosion rate are the rotational speed of 600 rpm and transverse speed of 70 mm/min.
... Additionally, the detrimental effect of the secondary particles on corrosion resistance increases as particles size enhances [40]. Gharavi et al. [41] noted that intermetallic particles size increases as the temperature during FSW increases. Presence of water as the coolant, during FSSW and FSSVW processes, decreases the temperature and impedes the growth of intermetallic particles. ...
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... A slightly elongated grain structure can be seen in the TMAZ zone due to the annealing effect of heat and severe plastic deformation of material around the pin edge [22]. Slightly coarse grains were seen in the HAZ zone located outside of the TMAZ zone which was affected only by the heat generation during the welding process [23]. DXZ is of great industrial interest due to the new grains being smaller than the initial grains that enhances the mechanical properties at room temperature. ...
The aim of this work is to assess the influence of Friction Stir Welding (FSW), process parameters, optimized tool traveling speed, and corrosion resistance of the 0.95 Mg-Al-alloy and pure copper weldment. Samples of aluminum-copper with and without deformation were characterized to investigate the metallurgical effects created during the welding deformation process. Effect of process parameters on microstructure and corrosion rate have been investigated for all the samples. All the electrochemical and polarization tests were done in 3.5 wt.% NaCl solution. Scanning Kelvin Probe (SKP) was done to detect the localized corrosion on the surface. Optical micrography observation indicated that the primary α-Al phase, which was formed during solidification can effectively limit the growth of Cu9Al4 phase. Finer acicular α-Al precipitates were observed in CuAl matrix during joining process that tends to coarser with the increase in tools travel speed. The electrochemical and polarization results showed that among all the tool travelling speed the specimen joined at tool travelling speed of 40 mm/min shows the best non-corrosive property.
... Hence, nugget area contained more of the anodic V-95 alloy, which explains the higher corrosion susceptibility. Gharavi et al. 24 has also reported that pitting corrosion resistance of friction stir lap welded AA6061-T6 decreases along the through-thickness direction of the weld nugget. The residual stress in a weld joint varies in the through-thickness direction of the nugget. ...
This study has been undertaken to evaluate the electrochemical behavior of friction stir lap welded V-95CHT1 and D19CHT plates and to study the effect of post weld heat treatment on the corrosion characteristics of the welded alloys. The corrosion characteristics were tested as per ASTM G-34 standard by immersion in EXCO solution and analyzing the corroded plates through optical imaging and scanning electron microscopic analysis. Cyclic polarization tests were also undertaken to validate the results of the immersion test. It was observed that friction stir lap weld had sensitized the V-95 plate with the heat-affected zone of the joint found most susceptible and weld nugget least susceptible to corrosion. Corrosion resistance of the welded plates was also found to be higher for those joints that were welded employing process parameters providing higher weld heat input. Post weld retrogression and re-aging heat treatment was also found to be beneficial in increasing the corrosion resistance of the alloy.
... The corrosion of aluminum alloy friction stir welding commonly investigated using methods such as immersion test, polarization techniques, electrochemical impedance spectroscopy (EIS), and cyclic polarization tests are reported by many researchers [9][10][11]. ...
... The corrosion of aluminum alloy friction stir welding commonly investigated using methods such as immersion test, polarization techniques, electrochemical impedance spectroscopy (EIS), and cyclic polarization tests are reported by many researchers [9][10][11]. ...
Layered double hydroxide (LDH) conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3, prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide (AA2024-T3/CF-PPS). Vanadate was used as a model corrosion inhibitor. Lap shear testing method revealed an increase of 15% of the joint’s adhesion performance when treated with LDH and before exposure to salt spray. The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species. The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints, even after 6 weeks of salt spray. However, the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints. The effect of the galvanic corrosion was further investigated by zero resistance ammeter measurements as well as localized scanning vibrating electrode technique.
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AA 5052 H32 aluminum alloy is one of the most commonly used materials in the marine environment due to its good formability, good weldability, and better corrosion resistance. Assessment of resistance of welds of the alloy against corrosion is necessary for reliable design. In the present study, pitting and intergranular corrosion behavior of tungsten inert gas (TIG), normal friction stir welding (FSW), and underwater FSW (UFSW) joints of AA 5052 H32 aluminum alloy and parent alloy are investigated. Electrochemical corrosion behavior by Tafel polarization technique and intergranular corrosion susceptibility by mass loss of the specimen in concentrated nitric acid solution are studied as per ASTM standards. The corrosion studies were conducted on welded plates for which welding parameters during TIG welding and FSW were kept optimum for maximum tensile strength. The result shows that corrosion resistance of welded joints is inferior to that of parent metals. Corrosion resistance of the FSW joint and UFSW joint are nearly equal and found to be higher compared with the TIG joint. Density and size of pits formed on the parent metal and welded joints are examined via macro- and microscopic analysis and atomic force microscopic study. Results also show that the specimens welded by FSW and UFSW processes are immune to intergranular corrosion attack.
