scholarly journals Post-FSW Cold-Rolling Simulation of ECAP Shear Deformation and Its Microstructure Role Combined to Annealing in a FSWed AA5754 Plate Joint

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1526 ◽  
Author(s):  
Marcello Cabibbo ◽  
Chiara Paoletti ◽  
Mohamed Ghat ◽  
Archimede Forcellese ◽  
Michela Simoncini
Keyword(s):  
Cold Rolling ◽  
Shear Deformation ◽  
Volume Fraction ◽  
Base Material ◽  
Sheet Thickness ◽  
Annealing Treatment ◽  
Grain Structure ◽  
Friction Stir ◽  
Size Refinement ◽  
Angular Pressing

Friction stir welds are considered reliable joints for their lack of voids, cracks and distortions. When compared to the base material, friction stir welding (FSW) joints typically exhibit finer grain structured (especially at the nugget zone, NZ). Similarly, refined grain structure can also be obtained by severe plastic deformation (SPD) techniques, such as equal channel angular pressing (ECAP). In fact, the fine grain structures produced within the NZ of FSW or friction stir processed (FSP) materials are usually coarser than the ones achieved by ECAP. The former is characterized by lower dislocation density, higher high-angle boundary fraction and different mechanical strength, compared to what can be obtained by ECAP. In this study, a dedicated cold-rolling (CR) set-up, specifically designed to simulate an ECAP-equivalent shear deformation, was used to further refine the grain structure of FSW AA5754 sheets. The effect of ECAP-equivalent deformation induced by CR in a 2 mm-thick AA5754-H111 FSW joint was investigated. FSW was carried out at two different rotational (ω) and translational (v) welding speeds, 600 rpm, 200 mm/min and 1800 rpm, 75 mm/min, respectively. FSW sheets were then CR to obtain an equivalent shear strain of ε ~ 1.08, that is equivalent to 1-ECAP pass carried out with an internal die channels intersecting at an angle φ = 90° with a curvature extending over an angle Ψ = 20°. By CR, the sheet thickness reduced only by ~20%. The role of annealing on the FSW and CR plastically deformed AA5754 was also investigated. This was applied either prior or after FSW, and it resulted that whenever it follows the FSW, the mean volume fraction of dispersoids and Mg-rich particles is higher than the case of annealing preceding the FSW process. On the contrary, it was found that the annealing treatment had a minimal role on the dispersoids and particles mean size. The here reported post-FSW ECAP-simulated deformation, obtained by a customized CR process, showed sheet integrity and a significant concurrent grain size refinement.

Characterization of the vibration, stability and static responses of graphene-reinforced sandwich plates under mechanical and thermal loadings using the refined shear deformation plate theory

2021 ◽  
pp. 109963622199386
Author(s):  
Hessameddin Yaghoobi ◽  
Farid Taheri
Keyword(s):  
Shear Deformation ◽  
Volume Fraction ◽  
Plate Theory ◽  
Micromechanical Model ◽  
Sheet Thickness ◽  
Analytical Investigation ◽  
Sandwich Plates ◽  
Simply Supported ◽  
Vibration Stability ◽  
Shear Deformation Plate Theory

An analytical investigation was carried out to assess the free vibration, buckling and deformation responses of simply-supported sandwich plates. The plates constructed with graphene-reinforced polymer composite (GRPC) face sheets and are subjected to mechanical and thermal loadings while being simply-supported or resting on different types of elastic foundation. The temperature-dependent material properties of the face sheets are estimated by employing the modified Halpin-Tsai micromechanical model. The governing differential equations of the system are established based on the refined shear deformation plate theory and solved analytically using the Navier method. The validation of the formulation is carried out through comparisons of the calculated natural frequencies, thermal buckling capacities and maximum deflections of the sandwich plates with those evaluated by the available solutions in the literature. Numerical case studies are considered to examine the influences of the core to face sheet thickness ratio, temperature variation, Winkler- and Pasternak-types foundation, as well as the volume fraction of graphene on the response of the plates. It will be explicitly demonstrated that the vibration, stability and deflection responses of the sandwich plates become significantly affected by the aforementioned parameters.

scholarly journals Increase in the Mechanical Strength of Mg-8Gd-3Y-1Zn Alloy Containing Long-Period Stacking Ordered Phases Using Equal Channel Angular Pressing Processing

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 221 ◽  
Author(s):  
Gerardo Garces ◽  
Pablo Pérez ◽  
Rafael Barea ◽  
Judit Medina ◽  
Andreas Stark ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Yield Stress ◽  
Equal Channel Angular Pressing ◽  
Volume Fraction ◽  
Extrusion Direction ◽  
Grain Structure ◽  
Long Period ◽  
Angular Pressing ◽  
Β Phase ◽  
Ordered Phases

The evolution of the microstructure and mechanical properties during equal channel angular pressing processing has been studied in an extruded Mg-Gd-Y-Zn alloy containing long-period stacking ordered phases. After extrusion, the microstructure is characterized by the presence of long-period stacking ordered fibers elongated along the extrusion direction within the magnesium matrix. The grain structure is a mixture of randomly oriented dynamic recrystallized and coarse highly oriented non-dynamic recrystallized grains. Rare-earth atoms are in solid solution after extrusion at 400 °C and precipitation takes place during the thermal treatment at 200 °C. Precipitation of β’ prismatic plates and lamellar γ’ in the basal plane increases the tensile yield stress from 325 to 409 MPa. During equal channel angular pressing processing at 300 °C, the volume fraction of dynamic recrystallized grains continuously increases with the strain introduced during the equal channel angular pressing process. Precipitation of β phase is equally observed at grain boundaries of the ECAPed alloy. Dynamic recrystallized grain size decreases from 1.8 µm in the extruded material to 0.5 µm in the ECAPed alloy. Thermal treatment at 200 °C of ECAPed materials results in an increase of the yield stress up to 456 MPa, which is maintained up to 200 °C.

Superplasticity of Friction-Stir Welded Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure Obtained by Warm Severe Plastic Deformation

2016 ◽  
Vol 879 ◽  
pp. 2395-2400 ◽  
Author(s):  
Sergey Malopheyev ◽  
Sergey Mironov ◽  
Igor Vysotskiy ◽  
Rustam Kaibyshev
Keyword(s):  
Large Scale ◽  
Base Material ◽  
High Strength ◽  
Testing Temperature ◽  
Total Elongation ◽  
Friction Stir ◽  
Fine Grained ◽  
Angular Pressing ◽  
Elongation To Failure ◽  
Superplastic Properties

High-strength sheets of Al-5.4Mg-0.2Sc-0.1Zr alloy were produced by equal-channel angular pressing (ECAP) to 12 passes via route BC at 300 °C (573 K) followed by isothermal rolling at 300 °C (573 K) to a total thickness reduction of 80%. The final sheets with ultra-fine grained (UFG) structure were joined by friction stir welding (FSW). The tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to welding direction. The material demonstrated excellent superplastic properties in the range of temperatures from 350 (623 K) to 450 °C (723 K) at strain rates ranging from 8.3×10-3 s-1 to 3.3×10-1 s-1. The base material was found to be prone to abnormal grain growth at the testing temperature. This led to localization of the superplastic deformation in the stir zone section of the joints and thus limited total elongation-to-failure. The relationship between superplastic ductility and microstructure and application of this technique for the fabrication of large-scale superplastic sheets are discussed.

scholarly journals Application of Imaging Techniques to Determine the Post-Yield Behaviour of the Heterogeneous Microstructure of Friction Stir Welds

2021 ◽  
Author(s):  
S. Ramachandran ◽  
A. K. Lakshminarayanan ◽  
P. A. S. Reed ◽  
J. M. Dulieu-Barton
Keyword(s):  
Tool Wear ◽  
Mechanical Behaviour ◽  
Base Material ◽  
Grain Morphology ◽  
Stir Zone ◽  
Image Correlation ◽  
Grain Structure ◽  
Weld Nugget ◽  
Heterogeneous Microstructure ◽  
Friction Stir

Abstract Background Friction Stir Welding (FSW) causes intense plastic deformation and consequent thermomechanical interactions resulting in a localised heterogeneous microstructure. To understand the weld mechanical behaviour, it is necessary to identify each microstructural sub-region in the weld. Objective Determine the relationship between the local microstructure and mechanical behaviour of the different microstructural regions in a FSW. Methods Scanning electron microscopy (SEM) identified the microstructural sub-regions of an FSW joint. A novel High-Resolution Digital Image Correlation (HR-DIC) methodology enabled the determination of full-field strain response to provide the mechanical behaviour of the FSW sub-regions. X-ray computed tomography (CT) identified the geometry of the FSW and material composition. Results The grain morphology in the FSW varied in the stir zone with a fine grain structure in the weld nugget and larger grains in the thermomechanical affected zone (TMAZ); the grains were larger in the retreating side (RS) compared to the advancing side (AS). Tungsten deposits were found in the weld nugget and attributed to tool wear. The mechanical properties of the weld subregions showed that the material in the stir zone had a greater yield strength than the base material and the RS of the FSW was much more ductile than the weld nugget and the AS side. The tungsten distributions in the stir zone correlated with the local mechanical behaviour. Conclusions A novel methodology is developed that combines microstructural observations with HR-DIC enabling, for the first time, the FSW sub-region mechanical behaviour, to be related to the local grain morphology and inclusions caused by tool wear.

Microstructure of Friction-Stir-Welded High-Nitrogen Stainless Steel

2007 ◽  
Vol 539-543 ◽  
pp. 3757-3762 ◽  
Author(s):  
S.H.C. Park ◽  
Yutaka S. Sato ◽  
Hiroyuki Kokawa ◽  
Kazutaka Okamoto ◽  
Satoshi Hirano ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Nitrogen Content ◽  
Base Material ◽  
Welding Process ◽  
Grain Structure ◽  
Coarse Grain ◽  
High Nitrogen ◽  
Friction Stir ◽  
Fine Microstructure

Friction stir welding (FSW) was applied to a 0.53% nitrogen stainless steel. The nitrogen content change and the microstructural evolution in the weld were investigated. The nitrogen content analysis revealed that the stir zone (SZ) showed roughly the same nitrogen content as the base material (BM). This result suggests that FSW is an effective welding process for keeping up nitrogen content of high-nitrogen steel weld. The microstructural observation showed that the weld had the BM, the SZ, the partially recrystallized zone (PRZ) and the heat affected zone (HAZ). The coarse grain structure of the BM changed to relatively fine microstructure of equiaxially recrystallized austenite grain structure in the SZ during FSW. The PRZ contained both the fine and coarse grain structures. The detailed TEM observations showed that the particles with about 11m in size were present in the advancing side of the SZ both along grain boundaries and grain interiors. The Cr nitride less than 100 nm was formed in the HAZ along grain boundaries, which indicates that a slight sensitization occurred in the HAZ during FSW.

Processing, Superplastic Properties and Friction Stir Welding of Fine-Grained AZ31, AZ91, AE42 and QE22 Magnesium Alloys

2016 ◽  
Vol 838-839 ◽  
pp. 220-224 ◽  
Author(s):  
Talant Ryspaev ◽  
M. Janecek ◽  
Robert Kral ◽  
Volker Wesling ◽  
Lothar Wagner
Keyword(s):  
Friction Stir Welding ◽  
Grain Refinement ◽  
Magnesium Alloys ◽  
Mechanical Treatment ◽  
Base Material ◽  
Rate Sensitivity ◽  
Grain Structure ◽  
Friction Stir ◽  
Thermo Mechanical Treatment ◽  
Superplastic Properties

The grain refinement after thermo-mechanical treatment (TMT) was investigated in AZ91, AE42, und QE22 magnesium alloys. The optimal over-aging temperature was determined to be 300 °C in the case of AZ91 and AE42 alloys and 350 °C for QE22 alloy. After optimized TMT, the average grain sizes were 13.5 µm (AE42), 11.1 µm (AZ91) and 1.9 µm (QE22). The QE22 alloy exhibited the superior superplastic properties, with maximum elongation to failure 750 % and strain rate sensitivity parameter m=0.73. The Friction Stir Welding showed that the original base material grain structure of the alloys AZ31 and AZ91 replaced by ultrafine grains in the stir zone. The purpose of the present paper is to present the results of the grain refinement in magnesium alloys by thermo mechanical treatment and stir welding.

Effect of microstructure and precipitate formation on mechanical and corrosion behavior of friction stir processed AA6061 alloy using different cooling media

2021 ◽  
pp. 146442072110057
Author(s):  
Marukurti VNV Satyanarayana ◽  
Adepu Kumar ◽  
Shivraman Thapliyal
Keyword(s):  
Corrosion Resistance ◽  
Friction Stir Processing ◽  
Base Alloy ◽  
Base Material ◽  
Stir Zone ◽  
Grain Structure ◽  
Precipitate Formation ◽  
Friction Stir ◽  
Aa6061 Alloy ◽  
Effect Of Microstructure

The present work studies the effect of microstructure and precipitate formation on mechanical and corrosion characteristics of friction stir processed AA6061 alloy using different cooling technologies (cryogenic and water cooling). The results revealed that recrystallized fine grains formed in all friction stir processing samples (grain size within a range of 2–6 µm) as a result of dynamic recovery and recrystallization, while samples processed in cooling-assisted friction stir processing resulted in better grain refinement in the stir zone than in air-cooled friction stir processing. Three kinds of precipitates (Fe-based needle-shaped precipitates, Si-based round-shaped precipitates, and chain of small round-shaped Si-based precipitates) were identified in base material and friction stir processing samples. Compared to air-cooled friction stir processing, in cooling-assisted friction stir processing, the hardness and tensile strength increased but remained lower than for the base alloy due to the presence of high density Fe-based needle-shaped precipitates. The ductility after friction stir processing greatly improved due to thermal softening and dissolution of precipitates. The corrosion results demonstrated that the corrosion resistance greatly enhanced after friction stir processing due to uniform distribution of grain structure and discontinuous chain of small round-shaped Si-based precipitates in stir zone. Moreover, cooling-assisted friction stir processing resulted in improved corrosion resistance compared to air-cooled friction stir processing due to the formation of fine precipitates.

The Grain Structures in some 5000 Series Aluminium Alloys after Asymmetric Rolling and Annealing

2006 ◽  
Vol 519-521 ◽  
pp. 161-168 ◽  
Author(s):  
Hai Ou Jin ◽  
David J. Lloyd
Keyword(s):  
Volume Fraction ◽  
Sheet Thickness ◽  
Grain Structure ◽  
Second Phase ◽  
Asymmetric Rolling ◽  
Fine Grain ◽  
Grain Structures ◽  
Mean Grain Size ◽  
Large Particles ◽  
Continuous Recrystallization

The development of grain structures after asymmetric rolling (ASR) and annealing was investigated in Al-Mg alloys AA5754, AA5182 and AA5083. It has been demonstrated that a fine grain structure could be produced through continuous recrystallization, but it is strongly affected by the presence of large second phase particles. In AA5754 the volume fraction of large particles is relatively low and continuous recrystallization is able to occur throughout the sheet thickness, resulting in a fine grain structure of 2μm mean grain size. In AA5182 the fraction of large particles increases to a level that the continuous recrystallization occurs only in the sheet surface, whereas the sheet centre undergoes discontinuous recrystallization. The discontinuous recrystallization due to particle stimulated nucleation (PSN) is dominant in AA5083 so that no continuous recrystallization has been observed. The fully recrystallized grain structure is slightly finer in the ASR processed AA5083 than the conventionally rolled one.

Recrystallization during Annealing of a Cold Rolled Lean Duplex Stainless Steel

2012 ◽  
Vol 715-716 ◽  
pp. 550-550 ◽  
Author(s):  
Clara Herrera ◽  
Dirk Ponge ◽  
Dierk Raabe
Keyword(s):  
Stainless Steel ◽  
Cold Rolling ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Volume Fraction ◽  
Annealing Treatment ◽  
Grain Morphology ◽  
Duplex Stainless Steels ◽  
Lean Duplex Stainless Steel ◽  
Bamboo Structure

Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and formed by ferrite (30-70%) and austenite. They have high tensile strength, good toughness and weldability and excellent corrosion resistance including stress-corrosion cracking and resistance to localized corrosion. The increase of the raw materials of the last years, there has been a motivation to develop new stainless steels with lower contents of nickel and molybdenum. Lean duplex stainless steels (LDSSs) are almost Mo free and nickel content lower than 4%. The lean duplex grades are expected to substitute not only 304/316 grades but also other duplex stainless steel grades. LDSSs are used for structural applications and for the less corrosion conditions such as liquor tanks and suction rolls. The aim of the present work was to study the kinetics of recovery and recrystallization of the lean duplex stainless steel 1.4362 during annealing treatment. The material was subjected to hot rolling and cold rolling of 70%, annealing treatment for different times at temperatures from 1000 to 1100°C and subsequently water quenched. Optical microscopy and electron back scattering diffraction (EBSD) were employed to study the evolution of the microstructure during the annealing treatment. After cold rolling austenite exhibited more strain hardening than ferrite. Consequently, the driving force of the austenite for recrystallization is higher. During annealing, recovery took place in ferrite, while the austenite remained nearly unrecovered until beginning of recrystallization. The layered grain morphology produced during cold rolling remained after the annealing treatment. The volume fraction of the phases did not show significant changes with the annealing time. Nevertheless, the volume fraction of austenite decline with an increasing of annealing temperature. After 60 seconds at 1100°C, annealing primary recrystallization had progressed in both phases, which show a bamboo-structure where the grain boundaries ran perpendicular to the phase boundaries. Grain growth progressed for longer annealing times. After 600 seconds, the bamboo-structure started to change for a more globular grain structure, pearl-structure. It continued and became more pronounced at longer annealing times. At lower temperatures, the recrystallization behavior is similar; however, the structure was refined. Recovery is favored by the high stacking fault energy of ferrite and the layered grain morphology. The lean duplex stainless steel 1.4362 shows a similar recrystallization kinetics compare with standard duplex stainless steels.

The Effect of Aluminum Clad on the Electrochemical Properties of the Similar Weld of Friction-Stir Welding of 2524

2011 ◽  
Vol 311-313 ◽  
pp. 1920-1923
Author(s):  
Chang Bin Shen ◽  
Jia Yan Zhang ◽  
Ji Ping Ge ◽  
Feng Yan
Keyword(s):  
Weight Loss ◽  
Friction Stir Welding ◽  
Potentiodynamic Polarization ◽  
Base Material ◽  
Polarization Curves ◽  
Grain Structure ◽  
Friction Stir ◽  
Potentiodynamic Polarization Curves ◽  
Dynamical Recrystallization ◽  
Equiaxed Grain

Microstructures, static weight loss and potentiodynamic polarization curves were carried out on the Friction-stir welds of Al clad 2524 alloy with the thickness of 1.35 mm. The results indicated that the microstructures of the Nugget had been remarkably reshaped. A dynamical recrystallization took place on the zone of the weld nugget and an equiaxed grain structure formed. The static weight loss and potentiodynamic polarization curves results indicated that the resistance of corrosion of the base material (with aluminum clad) was superior to that of its weld, but the anti-corrosive ability of the weld was superior to that of the base material without aluminum clad.

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