scholarly journals Internal Material Flow Layers in AA6082-T6 Butt-Joints during Bobbin Friction Stir Welding

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1059 ◽  
Author(s):  
Tamadon ◽  
Pons ◽  
Clucas ◽  
Sued
Keyword(s):  
Friction Stir Welding ◽  
Grain Boundaries ◽  
Material Flow ◽  
Internal Flow ◽  
High Density ◽  
Butt Joints ◽  
Friction Stir ◽  
Discontinuous Flow ◽  
Flow Features ◽  
Oxidation Layers

Bobbin friction stir welding with a double-sided tool configuration produces a symmetrical solid-state joint. However, control of the process parameters to achieve defect-free welds is difficult. The internal flow features of the AA6082-T6 butt-joints in bobbin friction stir welding were evaluated using a set of developed reagents and optical microscopy. The key findings are that the dark curved patterns (conventionally called 'flow-arms'), are actually oxidation layers at the advancing side, and at the retreating side are elongated grains with a high-density of accumulation of sub-grain boundaries due to dynamic recrystallization. A model of discontinuous flow within the weld is proposed, based on the microscopic observations. It is inferred that the internal flow is characterized by packets of material ('flow patches') being transported around the pin. At the retreating side they experience high localized shearing at their mutual boundaries, as evidenced in high density of sub-grain boundaries. Flow patches at the advancing side are stacked on each other and exposed to oxidization.

scholarly journals EBSD Characterization of Bobbin Friction Stir Welding of AA6082-T6 Aluminium Alloy

2020 ◽  
Vol 20 (4) ◽  
pp. 49-74 ◽  
Author(s):  
A. Tamadon ◽  
D. J. Pons ◽  
D. Clucas
Keyword(s):  
Friction Stir Welding ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Internal Flow ◽  
State Transformation ◽  
Friction Stir ◽  
Grain Fragmentation ◽  
Dynamic Recrystallisation ◽  
Size And Morphology

AbstractElectron Backscatter Diffraction (EBSD) was used to determine microstructural evolution in AA6082-T6 welds processed by the Bobbin Friction Stir Welding (BFSW). This revealed details of grain-boundaries in different regions of the weld microstructure. Different polycrystalline transformations were observed through the weld texture. The Stirring Zone (SZ) underwent severe grain fragmentation and a uniform Dynamic Recrystallisation (DRX). The transition region experienced stored strain which changed the grain size and morphology via sub-grain-boundary transformations. Other observations were of micro-cracks, the presence of oxidization, and the presence of strain hardening associated with precipitates. Flow-arms in welds are caused by DRX processes including shear, and low and high angle grain boundaries. Welding variables affect internal flow which affects microstructural integrity. The shear deformation induced by the pin causes a non-uniform thermal and strain gradient across the weld region, leading to formation of mixed state transformation of grain morphologies through the polycrystalline structure. The grain boundary mapping represents the differences in DRX mechanism I different regions of the weld, elucidates by the consequences of the thermomechanical nature of the weld. The EBSD micrographs indicated that the localised stored strain at the boundary regions of the weld (e.g. flow-arms) has a more distinct effect in emergence of thermomechanical nonuniformities within the DRX microstructure.

Numerical Investigation on Dissimilar Friction Stir Welding of Aluminum and Magnesium Sheets

2014 ◽  
Vol 622-623 ◽  
pp. 532-539 ◽  
Author(s):  
Gianluca Buffa
Keyword(s):  
Friction Stir Welding ◽  
Solid State ◽  
Material Flow ◽  
Welding Process ◽  
Correct Choice ◽  
Mutual Position ◽  
Main Field ◽  
Butt Joints ◽  
Friction Stir ◽  
Dissimilar Friction Stir Welding

Friction Stir Welding (FSW) is a solid-state welding process used to weld difficult to be welded or unweldable materials as aluminum alloys. In the last years other materials have been successfully tested as magnesium, titanium and nickel based alloys. Mixed joints can be obtained by FSW but issues arise in the correct choice of the process parameters. In the paper a numerical model is presented for the prediction of the main field variables distribution and the occurring material flow in FSW of dissimilar AA6061 and AZ31 butt joints. Important insights are obtained on the effect of the mutual position of the two materials with respect to the advancing and retreating side of the joint has been highlighted.

scholarly journals Analogue Modelling of Flow Patterns in Bobbin Friction Stir Welding by the Dark-Field/Bright-Field Illumination Method

2020 ◽  
Vol 20 (1) ◽  
pp. 56-70 ◽  
Author(s):  
A. Tamadon ◽  
D. J. Pons ◽  
D. Clucas
Keyword(s):  
Friction Stir Welding ◽  
Weld Zone ◽  
Welding Process ◽  
Internal Flow ◽  
Flow Patterns ◽  
Dark Field ◽  
Bright Field ◽  
Analogue Model ◽  
Friction Stir ◽  
Flow Features

AbstractThe flow-inducing effect of the bobbin-tool features (tri-flat pin and scrolled shoulder) were replicated by a simple analogue model for aluminium welds by layered plasticine samples. Flow patterns of the weld zone were clarified by a typical stereomicroscopy instrument assisted by dark-field/bright-field illumination. The effects of the pin features, specifically threads and flats in centre of bond zone and scrolled shoulder in sides of stirred zone, were identified. This study shows that internal flow features for BFSW welds is transferable from the friction stir welding process to the functional metal forming processes such where the shearing can extensively affect the microstructure. The similarity between the flow pattern of the provided aluminium samples and the plasticine analogue can validate the accuracy of the flow model presented in this work.

Thermo-Mechanical Modelling of Friction Stir Welding Process

2013 ◽  
Vol 774-776 ◽  
pp. 1155-1159 ◽  
Author(s):  
Xiao Cong He
Keyword(s):  
Finite Element Analysis ◽  
Friction Stir Welding ◽  
Mechanical Behaviour ◽  
Material Flow ◽  
Welding Process ◽  
Element Analysis ◽  
Friction Stir ◽  
Mechanical Modelling ◽  
Major Factors ◽  
Realistic Prediction

Friction stir welding (FSW) is a solid-state welding process where no gross melting of the material being welded takes place. Numerical modelling of the FSW process can provide realistic prediction of the thermo-mechanical behaviour of the process. Latest literature relating to finite element analysis (FEA) of thermo-mechanical behaviour of FSW process is reviewed in this paper. The recent development in thermo-mechanical modelling of FSW process is described with particular reference to two major factors that influence the performance of FSW joints: material flow and temperature distribution. The main thermo-mechanical modelling used in FSW process are discussed and illustrated with brief case studies from the literature.

Microstructure and Mechanical Properties at the Unsteady Areas of Non-Linear Friction Stir Welding

2007 ◽  
Vol 561-565 ◽  
pp. 1059-1062 ◽  
Author(s):  
H. Takahara ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Y. Okawa ◽  
Kenji Higashi
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Welding Parameter ◽  
Butt Joints ◽  
Friction Stir ◽  
Non Linear ◽  
Linear Friction ◽  
Fsw Parameters ◽  
Five Axis ◽  
Welding Direction

The influence of tool control in non-linear friction stir welding (FSW) on mechanical properties of joints was investigated. FSW is widely applied to linear joints. It is impossible for five axis FSW machines, however, to keep all the FSW parameters in optimum conditions at non-linear welding. Non-linear FSW joints should be made by compromise with the order of priority for FSW parameters. The tensile test results of butt joints with rectangular change in welding direction on plate plane (L-shaped butt joints) with various welding parameter change. It was found that turn to the retreating side is encouraged when welding direction change. And the method of zero inclination tool angle is effective at non-linear and plane welding.

Grain Structure Formation Ahead of Tool during Friction Stir Welding of AZ31 Magnesium Alloy

2010 ◽  
Vol 160 ◽  
pp. 313-318 ◽  
Author(s):  
Uceu Suhuddin ◽  
Sergey Mironov ◽  
H. Takahashi ◽  
Yutaka S. Sato ◽  
Hiroyuki Kokawa ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Magnesium Alloy ◽  
Structure Formation ◽  
Material Flow ◽  
Boundary Migration ◽  
Deformation Mode ◽  
Grain Structure ◽  
Az31 Magnesium Alloy ◽  
Structure Evolution ◽  
Friction Stir

The “stop-action” technique was employed to study grain structure evolution during friction-stir welding of AZ31 magnesium alloy. The grain structure formation was found to be mainly governed by the combination of the continuous and discontinuous recrystallization but also involved geometric effect of strain and local grain boundary migration. Orientation measurements showed that the deformation mode was very close to the simple shear associated with the rotating pin and material flow arose mainly from basal slip.

Influence of Tool Geometry and Contact Condition on Friction Stir Welding of Al-Cu Laminated Composites

2013 ◽  
Vol 856 ◽  
pp. 16-21
Author(s):  
R. Beygi ◽  
Mohsen Kazeminezhad ◽  
A.H. Kokabi ◽  
S. Mohammad Javad Alvani ◽  
D. Verdera ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Material Flow ◽  
Laminated Composites ◽  
Flow Behavior ◽  
Tool Geometry ◽  
Contact Conditions ◽  
Friction Stir ◽  
Tool Geometries ◽  
Welding Procedure ◽  
Sem Analyses

In this study friction stir welding of Al-Cu laminated composites were carried out by two different tool geometries. Welding procedure was carried out from both sides of Al and Cu. Analyzing cross section of welds showed that different contact conditions between shoulder and material, offers different material flow behavior which is dependent on the tool geometry. SEM analyses showed that mixing of materials in nugget region is more pronounced in the advancing side. Also XRD results indicated that welding from Cu side, leads to intermetallic formation in mixed regions.

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