How microstructure affects localized corrosion resistance of stir zone of the AA2198-T8 alloy after friction stir welding

Dissimilar friction stir welding of AA5083-AA6061 alloys in different cooling environments (air, liquid nitrogen, and water) was successfully employed as an alternative method to enhance corrosion resistance and mechanical properties. The evolution of microstructure, corrosion behavior, and mechanical properties of friction stir welded joints were studied using optical microscopy (OM), electron backscattered diffraction, scanning electron microscope, electrochemical workstation, and universal testing machine. The results indicated that the width of the stir zone and grain size of heat-affected zones were reduced by the use of external cooling media. Electron backscattered diffraction results showed that the grain size in air-cooled friction stir welding, nitrogen-cooled friction stir welding and water-cooled friction stir welding were 7.6 µm, 4.5 µm, and 3.2 µm, respectively, and water-cooled friction stir welding joint developed a larger fraction of high-angle grain boundaries at stir zone. The intermetallics formed in the joints using cooling media were finer compared to that of the air-cooled samples. The corrosion behavior of the stir zone was impacted by the cooling environment while potentiodynamic polarization results revealed that the water-cooled friction stir welding joint showed excellent corrosion resistance due to the finer size of intermetallics. The minimum hardness values shifted to the stir zone in the case of nitrogen-cooled friction stir welding and water-cooled friction stir welding from the heat-affected zone location as in the air-cooled friction stir welding joint. For the joint made with water-cooled friction stir welding, maximum yield strength was obtained with a joint efficiency of 96% relative to AA5083 base material.

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Localized Corrosion Resistance of Dissimilar Aluminum Alloys Joined by Friction Stir Welding (FSW)

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.710.41 ◽

2016 ◽

Vol 710 ◽

pp. 41-46 ◽

Cited By ~ 1

Author(s):

Aline F.S. Bugarin ◽

Fernanda Martins Queiroz ◽

Maysa Terada ◽

Hercílio G. De Melo ◽

Isolda Costa

Keyword(s):

Corrosion Resistance ◽

Aluminum Alloy ◽

Friction Stir Welding ◽

Aluminum Alloys ◽

Weight Ratio ◽

Base Material ◽

High Strength ◽

Localized Corrosion ◽

Friction Stir ◽

Dissimilar Aluminum Alloys

2XXX and 7XXX high strength aluminum alloys are the most used materials for structural parts of aircrafts due to their high strength/weight ratio. Their joining procedure is an engineering challenge since they present low weldability. Friction Stir Welding (FSW) is a joining technology developed in the early 90 ́s. It is a solid-state welding process, without the use of fillers or gas shield, that eliminates conventional welding defects and has been considered of great interest for application in the aircraft industry. FSW of aluminum alloys results in four regions of different microstructures, specifically: the base material (BM), the heat affected zone (HAZ), the thermo-mechanically affected zone (TMAZ), and the nugget zone (NZ). The complex microstructure of the weld region leads to higher susceptibility to localized corrosion as compared to the BM even when similar alloys are joined. The welding of dissimilar alloys in its turn results in even more complex microstructures as materials with intrinsically different composition, microstructures and electrochemical properties are put in close contact. Despite the great interest in FSW, up to now, only few corrosion studies have been carried out for characterization of the corrosion resistance of dissimilar Al alloys welded by FSW. The aim of this study is to investigate the corrosion behavior of aluminum alloy 2024-T3 (AA2024-T3) welded to aluminum alloy 7475-T761 (AA7475-T761) by FSW. The evaluation was performed in 0.01 mol.L-1 by means of open circuit potential measurements, polarization techniques and surface observation after corrosion tests.

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Corrosion Behavior and Microstructure of Stir Zone in Fe-30Mn-3Al-3Si Twinning-Induced Plasticity Steel after Friction Stir Welding

Metals ◽

10.3390/met10111557 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1557

Author(s):

Hye-Jin Kim ◽

Hidetoshi Fujii ◽

Seung-Joon Lee

Keyword(s):

Friction Stir Welding ◽

Electrochemical Impedance ◽

Coincidence Site Lattice ◽

Corrosion Property ◽

Stir Zone ◽

Localized Corrosion ◽

Corrosion Resistant ◽

Friction Stir ◽

Electrochemical Testing ◽

Polarization Test

The effect of friction stir welding on microstructure and corrosion property was studied in Fe-30Mn-3Al-3Si (wt.%) twinning-induced plasticity steel using both an electron backscattered diffractometer and electrochemical testing (i.e., polarization test and electrochemical impedance spectroscope). The stir zone has a relatively higher corrosion resistance with uniform dissolution on the surface despite after welding, whereas the base metal shows localized corrosion attack with deep and long degradation along the grain boundaries. This is due to the corrosion-resistant coincidence site lattice boundaries caused by discontinuous dynamic recrystallization via the grain boundary bulging during the friction stir welding.

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The Effect of Vibration during Friction Stir Welding on Corrosion Behavior, Mechanical Properties, and Machining Characteristics of Stir Zone

Metals ◽

10.3390/met7100421 ◽

2017 ◽

Vol 7 (10) ◽

pp. 421 ◽

Cited By ~ 5

Author(s):

Sajad Fouladi ◽

Amir Ghasemi ◽

Mahmoud Abbasi ◽

Morteza Abedini ◽

Amir Khorasani ◽

...

Keyword(s):

Mechanical Properties ◽

Friction Stir Welding ◽

Corrosion Behavior ◽

Stir Zone ◽

Friction Stir ◽

Machining Characteristics

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Effect of plasma preheating on weld quality and tool life during friction stir welding of DH36 steel

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1177/0954405421990139 ◽

2021 ◽

pp. 095440542199013

Author(s):

Avinish Tiwari ◽

Pardeep Pankaj ◽

Saurav Suman ◽

Piyush Singh ◽

Pankaj Biswas ◽

...

Keyword(s):

Friction Stir Welding ◽

Tool Life ◽

Force Measurement ◽

Deep Understanding ◽

High Strength ◽

Microstructural Characterization ◽

Stir Zone ◽

Friction Stir ◽

Allotriomorphic Ferrite ◽

Fsw Parameters

Friction stir welding (FSW) of high strength materials is challenging due to high tool cost and low tool life. To address this issue, the present investigation deals with an alternative of plasma-assisted friction stir welding (PFSW) of DH36 steel with WC-10%Co tool. Plasma preheating current (13 A, 15 A, and 17 A) was varied by keeping other FSW parameters as constant. During the FSW and PFSW process, force measurement and thermal history aided in a deep understanding of the process, tool degradation mechanisms, accompanied by the mechanical and microstructural characterization of the welded joints. The stir zone hardness was increased from 140 HV0.5 to about 267 HV0.5. The yield and tensile strength of weld increased from 385 MPa and 514 MPa to about 391 MPa and 539 MPa, respectively. Weld joint elongation (%) was increased from ~10% of weld 1 to ~13.89% of weld 4. During PFSW, the process temperature was increased, the cooling rate was lowered, and the weld bead was widened. The results also revealed that the plasma-assisted weld resulted in polygonal ([Formula: see text]) and allotriomorphic ferrite as the major constituents in the stir zone. Pearlite dissolution and spheroidization were observed in the ICHAZ and SCHAZ, respectively. Additionally, the plasma preheating reduced the tungsten tool’s wear by 58% compared to FSW.

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Friction Stir Welding with Low-Medium-High Tool Travel Speed of 0.95 Mg-Al-Alloy and Pure Copper: Electrochemical and Surface Studies

10.20944/preprints201812.0039.v1 ◽

2018 ◽

Author(s):

Neetesh Soni ◽

Ambrish Singh

Keyword(s):

Friction Stir Welding ◽

Process Parameters ◽

Pure Copper ◽

Travel Speed ◽

Localized Corrosion ◽

Al Alloy ◽

Kelvin Probe ◽

Friction Stir ◽

Surface Optical ◽

Joining Process

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.

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Stir zone material flow patterns during friction stir welding of heavy gauge AA5056 workpieces and stability of its mechanical properties

Metal Working and Material Science ◽

10.17212/1994-6309-2021-23.4-140-154 ◽

2021 ◽

Vol 23 (4) ◽

pp. 140-154

Author(s):

Tatiana Kalashnikova ◽

◽

Vladimir Beloborodov ◽

Kseniya Osipovich ◽

Andrey Vorontsov ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Friction Stir Welding ◽

Elevated Temperatures ◽

Thin Sheet ◽

Stir Zone ◽

Clear Correlation ◽

Material Structure ◽

Friction Stir ◽

Significant Difference

Introduction. Friction stir welding and processing are almost identical processes of severe plastic deformation at elevated temperatures. These technologies differ mainly in the purpose of its use: the formation of a hardened surface layer or producing a welded joint. However, it is known that both during welding and during processing of heavy gauge workpieces temperature gradients occur. As a result, the conditions of adhesive interaction, material plastic flow, and the formation of the stir zone change as compared to thin-sheet workpieces with fundamentally different heat dissipation rates. In this connection, the purpose of the work is to determine the regularities of the structure formation and stability of the mechanical properties in different directions in the material of 35-mm-thick aluminum-magnesium alloy samples produced by friction stir welding/processing. Research Methodology. The technique and modes of friction stir welding and processing of AA5056 alloy workpieces with a thickness of 35 mm are described. Data on the equipment used for mechanical tests and structural research are given. Results and discussion. The data obtained show the excess mechanical properties of the processing zone material over the base metal ones in all studied directions. Material structure heterogeneities after friction stir welding/processing of heavy gauge workpieces have no determining effect on the stir zone properties. At the same time, there is no clear correlation between the tensile strength values and the load application direction, nor is there any significant difference in mechanical properties depending on the location of the samples inside the stir zone. The average ultimate tensile strength values in the vertical, transverse, and longitudinal directions are 302, 295 and 303 MPa, respectively, with the yield strength values of 155, 153 and 152 MPa, and the relative elongation of 27.2, 27.5, 28.7 %.

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Research on the Friction Stir Welding of Sc-Modified AA2519 Extrusion

Metals ◽

10.3390/met9101024 ◽

2019 ◽

Vol 9 (10) ◽

pp. 1024 ◽

Cited By ~ 5

Author(s):

Robert Kosturek ◽

Lucjan Śnieżek ◽

Janusz Torzewski ◽

Marcin Wachowski

Keyword(s):

Mechanical Properties ◽

Friction Stir Welding ◽

Base Material ◽

Stir Zone ◽

Welding Parameters ◽

Friction Stir ◽

Treated Condition ◽

Heat Treated ◽

Heat Treated Condition ◽

Fsw Parameters

The aim of this research was to investigate the effect of friction stir welding (FSW) parameters on microstructure and mechanical properties of Sc-modified AA2519 extrusion joints. The workpiece was welded by FSW in non-heat-treated condition with seven different sets of welding parameters. For each obtained joint macrostructure and microstructure observations were performed. Mechanical properties of joints were investigated using tensile test together with localization of fracture location. Joint efficiencies were established by comparing measured joints tensile strength to the value for base material. The obtained results show that investigated FSW joints of Sc-modified AA2519 in the non-heat-treated condition have joint efficiency within the range 87–95%. In the joints obtained with the lowest ratio of the tool rotation speed to the tool traverse speed, the occurrence of imperfections (voids) localized in the stir zone was reported. Three selected samples were subjected to further investigations consisting microhardness distribution and scanning electron microscopy fractography analysis. As the result of dynamic recrystallization, the microhardness of the base material value of 86 HV0.1 increased to about 110–125 HV0.1 in the stir zone depending on the used welding parameters. Due to lack of the strengthening phase and low strain hardening of used alloy the lack of a significantly softened zone was reported by both microhardness analysis and investigation of the fractured samples.

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Investigating the Effect of Friction Stir Welding on Microstructure and Corrosion Behaviour of Al-Zn-Mg Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.969.517 ◽

2019 ◽

Vol 969 ◽

pp. 517-523

Author(s):

Chaitanya Sharma ◽

Vikas Upadhyay

Keyword(s):

Corrosion Resistance ◽

Friction Stir Welding ◽

Base Metal ◽

Heat Affected Zone ◽

Corrosion Behaviour ◽

Metal Dissolution ◽

Nugget Zone ◽

Precipitate Morphology ◽

Friction Stir ◽

Secondary Precipitates

In this work, Friction Stir Welding (FSW) of alloy 7039 was carried out in T4 temper and resulting microstructure and corrosion behaviour of developed weld were studied. FSW transformed the starting microstructure of base metal and formed stirred zone (SZ) and heat affected zone (HAZ) with varying microstructure and precipitate morphology. The observed zones in welded joints exhibited decreased protection to corrosion resistance than base metal. Dissolution of secondary precipitates in SZ and occurrence of precipitate free zones (PFZs) in HAZ enhanced susceptibility to corrosion of HAZ and weld nugget zone (WNZ) than base metal.

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