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

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.

scholarly journals Friction Stir Welding of T-Joints: Experimental and Statistical Analysis

2019 ◽  
Vol 3 (2) ◽  
pp. 38 ◽  
Author(s):  
Ibrahim Sabry ◽  
Ahmed M. El-Kassas ◽  
Abdel-Hamid I. Mourad ◽  
Dinu Thomas Thekkuden ◽  
Jaber Abu Qudeiri
Keyword(s):  
Friction Stir Welding ◽  
Heat Affected Zone ◽  
Surface Defects ◽  
Welding Process ◽  
Travel Speed ◽  
Percentage Error ◽  
Nugget Zone ◽  
T Joints ◽  
Friction Stir ◽  
Full Factorial

T-welded joints are commonly seen in various industrial assemblies. An effort is made to check the applicability of friction stir welding for producing T-joints made of AA6063-T6 using a developed fixture. Quality T-joints were produced free from any surface defects. The effects of three parameters, such as the speed of rotation of the tool, axial force, and travel speed were analyzed. Correspondingly, mechanical characteristics such as tensile strength, hardness in three zones (thermal heat affected zone, heat affected zone, and nugget zone) and temperature distribution were measured. The full factorial analysis was performed with various combinations of parameters generated using factorial design and responses. Evident changes in the strength, hardness, and temperature profile were noticed for each combination of parameters. The three main parameters were significant in every response with p-values less than 0.05, indicating their importance in the friction stir welding process. Mathematical models developed for investigated responses were satisfactory with high R-sq and least percentage error.

scholarly journals Stress Corrosion Cracking of Friction Stir-Welded AA-2024 T3 Alloy

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2610 ◽  
Author(s):  
Marina Cabrini ◽  
Sara Bocchi ◽  
Gianluca D'Urso ◽  
Claudio Giardini ◽  
Sergio Lorenzi ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Strain Rate ◽  
Stress Corrosion ◽  
Base Metal ◽  
Stress Corrosion Cracking ◽  
Heat Affected Zone ◽  
Corrosion Cracking ◽  
Slow Strain Rate ◽  
Friction Stir ◽  
Aa 2024

The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.

Friction Stir Welding of Aluminum 7136-T76511 Extrusions for Aerospace Applications

2007 ◽  
Author(s):  
Carter Hamilton ◽  
Stanisław Dymek ◽  
Marek Blicharski
Keyword(s):  
Corrosion Resistance ◽  
Friction Stir Welding ◽  
Heat Affected Zone ◽  
Mechanical Test ◽  
Corrosion Testing ◽  
Qualitative Assessment ◽  
Welding Parameters ◽  
Friction Stir ◽  
Aerospace Applications ◽  
Residual Properties

This research program evaluates the residual properties of 7136-T76511 aluminum extrusions joined through friction stir welding (FSW). AA 7136 is a new aluminum alloy developed by Universal Alloy Corporation for high strength aerospace applications that also demand good corrosion resistance, such as those on the Boeing 787 or the Airbus A380. Mechanical and corrosion testing were performed on the baseline material and on panels friction stir welded at 175, 225, 250, 300, 350 and 400 RPM (all other welding parameters were held constant). Mechanical test results demonstrate that the highest joint efficiency, 74%, is achieved at 350 RPM, but for each weld condition, the elongation of the welded material is significantly reduced, 50 – 75%, from the baseline value. Fracture of the tensile specimens consistently occurred on the retreating side of the weld along the interface between the heat affected zone (HAZ) and the thermo-mechanically affected zone (TMAZ), independent of the rotational speed. Examination of fracture surfaces through SEM revealed microvoid nucleation and coalescence around secondary phase particles in the microstructure, as well as numerous stepped or laminar facets characteristic to both the baseline and welded conditions. Exfoliation corrosion testing revealed a performance gradient across the weld with the weld nugget rating the poorest at EC and the heat affected zone rating the best at EA. Qualitative assessment of corrosion resistance is supported by mass loss calculations between the baseline and welded conditions.

Precipitation-dependent corrosion analysis of heat treatable aluminum alloys via friction stir welding, a review

2021 ◽  
pp. 095440622110036
Author(s):  
Tanveer Majeed ◽  
Yashwant Mehta ◽  
Arshad N Siddiquee
Keyword(s):  
Plastic Deformation ◽  
Corrosion Resistance ◽  
Friction Stir Welding ◽  
Severe Plastic Deformation ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Behaviour ◽  
Al Alloys ◽  
Friction Stir ◽  
Precipitate Strengthening

Although the various advantages of novel Friction stir welding (FSW) process; the weld surfaces are subjected to various serious problems such as lower corrosion resistance, high susceptibility to stress corrosion cracking and poor joint fatigue strength due to complex material flow and severe plastic deformation during the welding process. Corrosion behaviour of friction stir welded (FSWed) precipitate strengthening Al alloys have significant impact on metallurgical and electrochemical properties of structures. In FSW of precipitate strengthening Al alloys the localized heat input and severe plastic deformation creating appreciable changes in microstructure and modifies the microchemistry and metallurgical characteristics of precipitates. The heterogeneous distribution of precipitates and precipitate free zones (PFZs) along the grain boundaries leads to variation in electrochemical behaviour across the weld zones and hence increasing the susceptibility of weld surface to various corrosion attacks such as intergranular corrosion, pitting corrosion, exfoliation corrosion, stress corrosion cracking and galvanic corrosion. However, the corrosion resistance of FSWed joints can be improved either by reducing the size or redissolve the coarsened precipitates within the joint or modifying the microchemistry by controlling the size, location and distribution of precipitates which largely determine the corrosion rate of the weld surfaces. Consequently, it is imperative to address the influence of material modifications during FSW on corrosion behaviour of weld surface. This review paper addresses the precipitate dependent corrosion behaviour of FSWed joints of heat treatable/precipitate strengthening Al alloys and the various effective methods either to reduce or eliminate the effect of corrosion attack in FSWed joints of heat treatable Al alloys.

scholarly journals Effect of Stirring Pin Rotation Speed on Microstructure and Mechanical Properties of 2A14-T4 Alloy T-Joints Produced by Stationary Shoulder Friction Stir Welding

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1938
Author(s):  
Haifeng Yang ◽  
Hongyun Zhao ◽  
Xinxin Xu ◽  
Li Zhou ◽  
Huihui Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Rotation Speed ◽  
Weld Nugget ◽  
Al Alloy ◽  
Nugget Zone ◽  
T Joints ◽  
Friction Stir ◽  
Stationary Shoulder ◽  
Microstructure And Mechanical Properties

In this study, 2A14-T4 Al-alloy T-joints were prepared via stationary shoulder friction stir welding (SSFSW) technology where the stirring pin’s rotation speed was set as different values. In combination with the numerical simulation results, the macro-forming, microstructure, and mechanical properties of the joints under different welding conditions were analyzed. The results show that the thermal cycle curves in the SSFSW process are featured by a steep climb and slow decreasing variation trends. As the stirring pin’s rotation speed increased, the grooves on the weld surface became more obvious. The base and rib plates exhibit W- or N-shaped hardness distribution patterns. The hardness of the weld nugget zone (WNZ) was high but was lower than that of the base material. The second weld’s annealing effect contributed to the precipitation and coarsening of the precipitated phase in the first weld nugget zone (WNZ1). The hardness of the heat affect zone (HAZ) in the vicinity of the thermo-mechanically affected zone (TMAZ) dropped to the minimum. As the stirring pin's rotation speed increased, the tensile strengths of the base and rib plates first increased and then dropped. The base and rib plates exhibited ductile and brittle/ductile fracture patterns, respectively.

Microstructure evolution mechanism of Al/Mg dissimilar joint during friction stir welding

2020 ◽  
Vol 117 (3) ◽  
pp. 311 ◽  
Author(s):  
Wei Chen ◽  
Wenxian Wang ◽  
Zepeng Liu ◽  
Decheng An ◽  
Ning Shi ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Flow Pattern ◽  
Microstructure Evolution ◽  
Ring Structure ◽  
Reflection Effect ◽  
Nugget Zone ◽  
Friction Stir ◽  
Flow Features ◽  
Differential Etching ◽  
Onion Ring

A butt friction stir welding (FSW) process was performed on 6061 Al and AZ31 Mg plates. The microstructure evolutions of the three main regions in the nugget zone (NZ) retained in the FSW joint were systematically investigated to clarify the joint formation mechanism during FSW. The differential etching of these microstructural features was found to produce very vivid flow features. During FSW, the material in the shoulder affected zone (SAZ) was mainly driven by the shoulder, and only a small amount of it was driven by the pin. A strip of Al transferred by the pin from the retreating side (RS) to the advancing side (AS) contacted and reacted with Mg, thus forming intermetallic compounds (IMCs) (e.g., Mg17Al12 and Al3Mg2). Due to the stirring action and tilted angle of the threaded pin, a banded structure (BS) feature tilted at approximately 45° was produced by the alternating lamellae of IMCs. The appearance of an onion ring structure occurred in the severely deformed zone (SDZ), which could be attributed to the reflection effect of the imaginary die wall. Finally, the overall flow pattern of the joint was obtained.

Mechanical and Corrosion Behavior of Pure Aluminium Added Friction Stir Weld Joint of Aluminium Alloy

2019 ◽  
Vol 821 ◽  
pp. 327-333
Author(s):  
Sunil Sinhmar ◽  
Dheerendra Kumar Dwivedi
Keyword(s):  
Friction Stir Welding ◽  
Aluminium Alloy ◽  
Corrosion Behavior ◽  
Weld Joint ◽  
Second Phase ◽  
Pure Aluminium ◽  
Nugget Zone ◽  
Friction Stir ◽  
Aluminium Addition ◽  
Aluminium Strip

Friction stir welding (FSW) of AA2014 aluminium alloy was performed by sandwiching pure aluminium (Al) in the form of strip between the abutting surfaces. Mechanical and corrosion behavior of weld joint with and without pure aluminium addition was compared. Friction stir welding was carried out at rotational speed of 931 rpm and traverse speed of 41 mm/min. Pure aluminium strip of 1 mm thickness was used for incorporating Al in weld nugget zone. Microstructure analysis was carried out using optical microscope and FESEM with energy dispersive spectroscopy (EDS). Microhardness and tensile testing were performed on the weld joints. Corrosion behavior was investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (Tafel) test. FESEM analysis was performed before and after corrosion test. Traces of pure aluminium strip were observed in the microstructure. The incorporated strip was found not to be uniformly distributed in the nugget zone. Pure aluminium addition reduced the extent of formation of the second phase particle in the nugget zone as compared to the normal FSW joint i.e. without Al addition. This metallurgical homogeneity resulted in better corrosion resistance of the Al added weld joint than the normal FSW joint.

scholarly journals Innovate Method for Friction Stir Welding of Al-Mg-Si Alloy Thin Plate

2019 ◽  
Vol 269 ◽  
pp. 02006
Author(s):  
Li Fu ◽  
Fenjun Liu
Keyword(s):  
Tensile Strength ◽  
Friction Stir Welding ◽  
Base Metal ◽  
High Speed ◽  
Thick Plate ◽  
Welding Parameters ◽  
Butt Joints ◽  
Friction Stir ◽  
High Rotation Speed ◽  
Precipitated Phases

Al-Mg-Si (6061-T6) alloy with 0.8 mm thick plate was welded successfully by use of high speed friction stir welding (FSW) technology. The microstructural characteristics and mechanical property of the butt joints prepared by high speed FSW were analyzed in detail, the influence of welding parameters, fixture condition and after welding heat treatment were also explored. The results shown that sound surface topography and defect-free bonding interface were observed in the nugget zone (NZ). The microhardness of the as-welded joint was lower than that of the base metal because of the welding heat effect. Compared with the conventional speed FSW, the number of β-Mg2Si, Al2CuMg and Al8Fe2Si precipitated phases existed in the high speed FSWed NZ increased, which made the microhardness in the NZ improved significantly. The rod-shaped precipitates (Mg2Si) have the greatest influence on the microhardness distributions. The maximum tensile strength of 301.8 MPa, which was 85.8% of the base metal, was obtained at high rotation speed of 8000 rpm and fast welding speed of 1500 mm/min. The tensile strength of the ultra-high speed FSWed butt joints were improved significantly by post-weld artificial aging, with a maximum joint efficiency of 90.4%.

scholarly journals A Comparative Investigation on Conventional and Stationary Shoulder Friction Stir Welding of Al-7075 Butt-Lap Structure

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1264 ◽  
Author(s):  
Yu Chen ◽  
Huaying Li ◽  
Xiaoyu Wang ◽  
Hua Ding ◽  
Fenghe Zhang
Keyword(s):  
Friction Stir Welding ◽  
Material Flow ◽  
Comparative Investigation ◽  
Flow Mode ◽  
Nugget Zone ◽  
Friction Stir ◽  
Stationary Shoulder ◽  
Average Grain Size ◽  
Al 7075

Both conventional friction stir welding (C-FSW) and stationary shoulder friction stir welding (S-FSW) were employed to join the Al-7075 butt-lap structure, then the microstructural evolution and mechanical characterization of all FSW joints were systematically studied. The C-FSW joint exhibited a rough surface with flashes and arc corrugations, while the surface of the S-FSW joint became smooth. Moreover, for the S-FSW joint, the shoulder-affected zone got eliminated and the material flow mode during FSW was changed owning to the application of stationary shoulder. Furthermore, in comparison to C-FSW, the lower welding heat input of S-FSW decreased the average grain size in the nugget zone and inhibited the coarsening of strengthening precipitates in the heat-affected zone, elevating the overall hardness for the S-FSW joint. In addition, the tensile strength of the S-FSW joint became higher compared to the C-FSW joint, and all the FSW joints failed inside the nugget zone attributing to the existence of hook defect. The sharp-angled hook defect deteriorated the plasticity of the C-FSW joint further, which was only 70% that of the S-FSW joint.

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