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.

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.

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

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1024 ◽  
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.

Experimental Estimation of Strain Rate during FSW of Al-Alloy Using Plane-Strain Compression

2008 ◽  
Vol 580-582 ◽  
pp. 299-302 ◽  
Author(s):  
Kunitaka Masaki ◽  
Yutaka S. Sato ◽  
Masakatsu Maeda ◽  
Hiroyuki Kokawa
Keyword(s):  
Strain Rate ◽  
Plane Strain ◽  
Travel Speed ◽  
Plane Strain Compression ◽  
Stir Zone ◽  
Grain Structure ◽  
Al Alloy ◽  
Strain Rates ◽  
Friction Stir ◽  
Grain Structures

Friction stir welding (FSW) makes the stir zone with fine recrystallized grain structure. The recrystallized grains would be formed through dynamic recrystallization at high temperatures and high strain-rate. The present study experimentally simulated the dynamically recrystallized microstructure of a friction stir welded Al alloy 1050 produced at 600 rpm rotation and 100 mm/min travel speed, using combination of the plane-strain compression at various strain rates and the subsequent cooling along the cooling cycle of FSW. The equiaxed grain structures similar to the microstructure of the stir zone were produced at strain rates between 0.1 and 32 s-1; the grain size decreased with increasing strain rate. Strain rate during the FSW could be estimated to be about 1.8 s-1. The present study suggests that plane-strain compression test can simulate the recrystallized grain structure of the friction stir welds.

Improvement in Mechanical and Metallurgical Properties of Friction Stir Welded 6061-T6 Aluminum Alloys through Cryogenic Treatment

2019 ◽  
Vol 969 ◽  
pp. 490-495
Author(s):  
K. Tejonadha Babu ◽  
S. Muthukumaran ◽  
C.H. Bharat Kumar ◽  
C. Sathiya Narayanan
Keyword(s):  
Aluminum Alloys ◽  
Welded Joints ◽  
Cryogenic Treatment ◽  
Base Material ◽  
Cryogenic Cooling ◽  
Stir Zone ◽  
Welding Parameters ◽  
Cooling Rates ◽  
Friction Stir ◽  
Metallurgical Properties

An investigation has been made to improve the properties of the friction stir welded (FSW) 6061-T6 aluminum alloys. A cryogenic thermal treatment is developed for the joints during welding and its effects on mechanical and metallurgical properties, and precipitates are evaluated at various welding parameters. The friction stir welded joints with cryogenic treatment attained the better properties than the without cryogenic treatment. The improvement of properties was attributed to the refinement of grain size and to the introduction of a reduction in the softening region of the welded joints. Under cryogenic cooling rates, joints were experienced to the low temperature environments and faster cooling rates, which are contributed to enhance the hardness of the stir zone and heat affected zone regions and the formation of fine grain structure in the stir zone. The results indicated that the formation of finer grains of less than 5 µm in the stir zone, which is smaller than the joints of without cryogenic treatment. Subsequently, mechanical properties drastically improved and the joints achieved a maximum joint efficiency of 74% of the base material

Micro Structural Changes in Welded AlCuLi-Alloys by Positron Annihilation Spectroscopy, SAXS and DSC

2016 ◽  
Vol 877 ◽  
pp. 387-392
Author(s):  
Danny Petschke ◽  
Torsten E.M. Staab
Keyword(s):  
Positron Annihilation ◽  
Structural Changes ◽  
Base Material ◽  
Positron Annihilation Spectroscopy ◽  
Weld Nugget ◽  
Scanning Calorimetry ◽  
Positron Annihilation Lifetime ◽  
Friction Stir ◽  
X Ray Scattering ◽  
Type Size

We follow changes in the micro structure at several distances from the weld nugget of friction stir welded AlCuLi-alloy (AA2198) plates occurring due to the tool movement and the created heat by employing different methods: Small Angle X-ray Scattering (SAXS), giving information on type, size and density of precipitates, Differential Scanning Calorimetry (DSC), giving information on formed precipitates by their dissolution signal, and positron annihilation lifetime spectroscopy (PALS), being sensitive to vacancies and dislocations as well as to the formation and growth of precipitates. We start by characterizing the base material as a reference and proceed via the heat-affected zone to the weld nugget. By the use of complementary methods, we obtain information on structure, kind and distribution of precipitates and correlate this with hardness measurements.

Mechanical Properties and Corrosion Resistance of Friction Stir Welded Dissimilar Aluminum Alloys 2219 to 5083

2015 ◽  
Vol 813-814 ◽  
pp. 203-207
Author(s):  
M. Koilraj ◽  
A. Sathesh Kumar ◽  
D.L. Belgin Paul ◽  
S.R. Koteswara Rao
Keyword(s):  
Base Material ◽  
Welding Process ◽  
Weld Nugget ◽  
Welding Parameters ◽  
General Corrosion ◽  
Test Results ◽  
Friction Stir ◽  
Dissimilar Aluminum Alloys ◽  
Shoulder Diameter ◽  
Mechanical Properties And Corrosion

In this paper, 6 mm thickness dissimilar aluminium alloys of 5083 (H321) and 2219 (O) butt joints were fabricated successfully by friction stir welding process. The quality joints were obtained for the welding parameters of 35 mm/min and 650 rpm with the shoulder diameter to pin diameter ratio as 3. Macrostructure study shows that the interface between the weld nugget and TMAZ is smooth and clear with a flow arm extending towards the top surface of the weld in the 2219 side. The boundary on the 5083 side between the weld nugget and the TMAZ was irregular. The obtained joint efficiency is around 92.57% based on the UTS of the softer material (AA2219). The tensile test results showed that the specimens failed in the heat affected zone of the softer base material 2219. The hardness values in the stirred zone are higher than the softer base material of alloy 2219. The friction stir welded dissimilar joint 2219-5083 exhibited better general corrosion characteristics than the 2219-2219 weld and 2219 base material.

Microstructures and Properties of Biological Mg-Zn-Y-Nd Alloy by Friction Stir Processing

2013 ◽  
Vol 745-746 ◽  
pp. 33-38 ◽  
Author(s):  
Shi Jie Zhu ◽  
Li Guo Wang ◽  
Jin Jin ◽  
Jing Wang ◽  
Yu Feng Sun ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Processing ◽  
Cast Alloy ◽  
Corrosion Current ◽  
Stir Zone ◽  
Grain Structure ◽  
Second Phase ◽  
Uniform Corrosion ◽  
Corrosion Properties ◽  
Friction Stir

In order to improve the mechanical properties and processing performance of the Mg alloys, and to prevent magnesium alloy from non-uniform corrosion and too fast degradation in the degradation process, the biological medical Mg-Zn-Y-Nd alloy was modified by the friction stir processing (FSP) technique in this paper. The microstructural evolution and phase constitute of the stir zone of Mg-Zn-Y-Nd alloy were investigated, the microhardness and the corrosion properties of the alloy after FSP process was studied. The results showed that the FSP parameters had significant influence on the stir zone and thermo-mechanically affected zone. The stir zone experienced severe plastic deformation and complete dynamic recrystallization after FSP. The stir zone consists of fine equiaxed recystallized grains, and thermo-mechanically affected zone (TMAZ) has deformed grain structure. The second phase distributed along grain boundaries in as-cast state was broken during the FSP and transformed into fine, uniform and dispersed particles in the grains. After FSP, the size of grains was reduced from 50μm (as-cast alloy) to 1-2μm. However, the second phase constitution didnt change. The alloy obtained good comprehensive mechanical properties after FSP. The microhardness of alloy after FSP increased from 39HV (as-cast alloy) to 64HV(FSPed alloy). The results of electrochemical tests in simulated body fluid showed that the corrosion potential of FSP alloy increased and corrosion current density decreased, which confirmed the uniform corrosion of FSPed alloy.

Friction Stir Welding of Aluminum Metal Matrix Composite Containers for Electric Components

2014 ◽  
Vol 611-612 ◽  
pp. 1445-1451 ◽  
Author(s):  
Jukka Pakkanen ◽  
Andreas Huetter ◽  
Cecilia Poletti ◽  
Norbert Enzinger ◽  
Christof Sommitsch ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Friction Stir Welding ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Base Material ◽  
Stir Zone ◽  
Friction Stir ◽  
Joint Geometry ◽  
Gas Tightness

For aerospace applications, light-weight boxes to protect and carry electronic equipment need to be sealed. The main requirements on the components are low thermal expansion and gas tightness. The common material for such an application is a metal matrix composite (MMC). The MMC suggested here consists of A356 aluminum alloy matrix with 15 vol.% SiC particle reinforcement. A safe limit for the electronic component inside the boxes during sealing is determined to be 180°C. Due to the boundary conditions gas tightness and low heat input, Friction Stir Welding (FSW) might be an alternative to the employed joining techniques. For the FSW process the T-Joint is the most appropriate joint geometry in respect to the box design. The geometry of the lid has to ensure the backing system for the stir zone inside the box. A successful welding of the box was done after a joint geometry optimization. The examination of the welded box concerns material characterization with microscopic methods, measuring thermal expansion in base material and stir zone and temperature measurement while FSW.

Investigation of Microstructure and Mechanical Properties of Friction Stir Lap Jointed Ni Base Superalloy

2012 ◽  
Vol 724 ◽  
pp. 481-485
Author(s):  
Kuk Hyun Song ◽  
Kazuhiro Nakata
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Friction Stir Welding ◽  
Base Material ◽  
Lap Joints ◽  
Stir Zone ◽  
Inconel 600 ◽  
Friction Stir ◽  
Microstructure And Mechanical Properties ◽  
Average Grain Size

This study evaluated the microstructure and mechanical properties of friction stir welded lap joints. Inconel 600 and SS 400 as experimental materials were selected, and friction stir welding was carried out at tool rotation speed of 200 rpm and welding speed of 100 mm/min. Applying the friction stir welding was notably effective to reduce the grain size of the stir zone, as a result, the average grain size of Inconel 600 was reduced from 20 μm in the base material to 8.5 μm in the stir zone. Joint interface between Inconel 600 and SS 400 showed a sound weld without voids and cracks. Also, the hook, along the Inconel 600 alloy from SS 400, was formed at advancing side, which directly affected an increase in peel strength. In this study, we systematically discussed the evolution on microstructure and mechanical properties of friction stir lap jointed Inconel 600 and SS 400.

scholarly journals Post corrosion tensile strength and failure of dissimilar friction stir welded aluminium alloys

2020 ◽  
Vol 326 ◽  
pp. 04008
Author(s):  
Madhav Raturi ◽  
Anirban Bhattacharya
Keyword(s):  
Tensile Strength ◽  
Aluminium Alloys ◽  
Base Material ◽  
Fracture Morphology ◽  
Stir Zone ◽  
Tensile Failure ◽  
Friction Stir ◽  
Corrosive Solution ◽  
Dissimilar Weld ◽  
Dissimilar Friction Stir Welding

The present study efforts towards appraising the effects of corrosion on the tensile and fracture behaviour of dissimilar friction stir welding (FSW) of aluminium alloys. Three different dissimilar FSW joints obtained between AA6061-T6 and AA7075-T651, AA6061-T6 and AA2014-T6, AA7075-T651 and AA2014-T6, using threaded pin profile with three flat faces (TIF) tool at rotational speed of 1200 rpm and welding speed of 98 mm/min. The maximum joint tensile strength was achieved for AA7075-AA2014 joints followed by AA6061-AA2014 and least recorded for AA6061-AA7075 for as obtained FSW joints (non-corroded). The joints are further immersed into a corrosive solution for 1, 2, 7 and 14 days duration. The corrosion occurred all over the joint but much accelerated rate of exfoliation corrosion exists away from stir zone near the confluence of heat affected zone and base material irrespective of the advancing or retreating side. With increase in corrosion time the location of tensile failure shifted towards corroded region (AA6061-T6) instead of stir zone in dissimilar weld joint AA6061-AA2014, whereas it remained unchanged for other two joints. The fractured surfaces of AA6061-AA2014 FSW joints reveals the articulated view of pits and fracture morphology advocating the loss in YS, UTS and % elongation with increases in immersion duration.

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