Corrosion behavior of spray formed 7055 aluminum alloy joint welded by underwater friction stir welding

Corrosion of Al alloys was examined by repeated wet-dry cycle tests with 5.5 M NaCl solution and pure water at 323 K and compared with immersion test corrosion. All Al alloy specimens after the immersion tests for 7 days in the NaCl solution showed preferential dissolution of the aluminum matrix around Si phases and Al 3 Fe intermetallic compounds, and in pure water showed formation of thick amorphous hydroxide films. The corrosion rate in pure water was higher than that in the NaCl solution. In the repeated wet-dry cycle test with NaCl solutions, a 0.02-ml droplet of 5.5 M NaCl solutions was initially dripped on specimens at 323 K and left for 690 s to allow the dry up of the droplet, resulting in solid NaCl precipitation. Then, the dissolution and precipitation of NaCl were repeated 150 times by dripping 0.02-ml pure water at 690-s intervals. At the edge of the droplet, pits with 20-100-μm diameter had formed after the 150 cycles, while, at the central areas, the corrosion behavior was similar to that observed in the NaCl immersion test. In similar cycle tests with pure water, dripping of water droplet was also repeated 150 times. Here, needle-like crystalline hydroxides formed at the edge of the droplet, while thick hydroxide films formed at the central areas, like in the pure water immersion test.

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“…2. The hydroxides formed at the edges are considered to crystallize to become pseudo-boehmite during the dried out period [24].…”

Section: Discussionmentioning

confidence: 99%

Corrosion of Al alloys in repeated wet-dry cycle tests with NaCl solution and pure water at 323 K

Chiba

Saito

Takahashi

et al. 2015

J Solid State Electrochem

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“…In FSW, a non-consumable rotating tool with a pin and a shoulder are inserted into plates to be joined at a specific load, rotational and welding speed 1 . Heat treatable aluminium alloys with good strength to weight ratios are commonly used in aircraft and aerospace applications 2 .In recent years, some of the researchers have used water to friction stir weld the various aluminium alloys [3][4][5][6][7] . In Submerged Friction Stir Welding (SFSW) process, the entire workpiece is immersed in a liquid environment during the friction stir welding.…”

Section: Introductionmentioning

confidence: 99%

Submerged Friction Stir Welding of 6061-T6 Aluminium Alloy under Different Water Heads

Rathinasuriyan

Santhanam

2018

Mat. Res.

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The aim of this paper is to determine the feasibility of submerged friction stir welding of 6061-T6 aluminium alloy on different water heads through macrostructuralanalysis.In this work, aluminium 6061-T6 alloy was friction stir welded under normal and submerged conditions at different rotational speeds of 400 rpm, 800 rpm, 1200 rpm, 1600 rpm. The water head was varied from 10 to 30 mm in the case of thesubmerged friction stir welding process. In both normal and submerged friction stir welding processes, a welding speed of 45 mm/min, a normal load of 30 kN, tool tilt angle of 2˚, depth of tool penetration and tool geometry were kept constant. Torque is measured during the welding process, and power (kW) is calculated after the welding process. The macrostructural analysis was carried out for locating defect formation and identifying the feasible working range of process parameters of the welded aluminium 6061-T6 alloy. The mechanical properties such as ultimate tensile strength and microhardness of submerged friction stir welded of 6061 aluminium alloys were investigated.Scanning Electron Microscope (SEM) metallography was used for comparing the microstructure of the parent material, friction stir welded and submerged stir welded samples.

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“…The welding methods used with dissimilar aluminum/steel are mostly solid-phase welding (such as friction welding, welding-brazing, etc.). However, the low efficiency and limits of size and shape of the workpiece mean these methods have difficulty in meeting the requirements of mass production, and this has restricted the application of the integrated structure of dissimilar aluminum/steel [6][7][8]. Meanwhile, there are some problems in the traditional welding of dissimilar aluminum/steel, including the different melting points of aluminum and steel, slag of joints formed by aluminum oxide film and so on.…”

Section: Introductionmentioning

confidence: 99%

Corrosion Behavior of Keyhole-Free Friction Stir Spot Welded Joints of Dissimilar 6082 Aluminum Alloy and DP600 Galvanized Steel in 3.5% NaCl Solution

Zhang

et al. 2017

Metals

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Abstract:The corrosion behavior of keyhole-free friction stir spot welded joints of dissimilar 6082 aluminum alloy and DP600 galvanized steel in 3.5% NaCl solution has been investigated by the immersion test and electrochemical analysis. The surface of the aluminum alloy produced exfoliation and pitting corrosion. The pitting occurred seriously on the interface of the 6082 aluminum alloy, but the steel had no corrosion. The corrosion galvanic couples were formed between elements of Si and Fe with a high electrode potential, and Mg and Al with a low electrode potential, around them. Mg and Al elements of Mg 2 Si and Si-containing solid-solution phase α (Al) preferentially became an anodic dissolution and formed exfoliation corrosion around the Si elements. Fe-rich phase θ (Al 3 Fe) as the cathode caused corrosion of Mg and formed pitting around Mg-rich phase β (Al 3 Mg 2 ) as the anode. The sequence of the corrosion resistance of different areas of the joints (with decreasing corrosion resistance) was WNZ (Weld Nugget Zone) > TMAZ (Thermo-mechanically Affected Zone) > BM (Base Metal) > HAZ (Heat-affected Zone). The joints of keyhole-free FSSW (Fiction Stir Spot Welding) of dissimilar 6082 aluminum alloy and DP600 galvanized steel have better corrosion resistance than base metal in 3.5% NaCl solution.

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Corrosion behavior of spray formed 7055 aluminum alloy joint welded by underwater friction stir welding

Cited by 68 publications

References 24 publications

Corrosion of Al alloys in repeated wet-dry cycle tests with NaCl solution and pure water at 323 K

Corrosion of Al alloys in repeated wet-dry cycle tests with NaCl solution and pure water at 323 K

Submerged Friction Stir Welding of 6061-T6 Aluminium Alloy under Different Water Heads

Corrosion Behavior of Keyhole-Free Friction Stir Spot Welded Joints of Dissimilar 6082 Aluminum Alloy and DP600 Galvanized Steel in 3.5% NaCl Solution

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