Dissimilar Friction Stir Welding Research Articles

Microstructure evolution and its effect on the corrosion of dissimilar aluminum alloys friction stir welding joint

Microstructural heterogeneity in weld nugget zone (WNZ) of dissimilar AA7050-AA2024 friction stir welding joint and its effect on galvanic corrosion (GC) were explored. The increase in solid-solutioned Zn content and the number of intergranular MgZn2 greatly worsens the corrosion resistance of local AA7050-WNZ, while the grain refinement and fragmented Al2Cu slightly improves that of local AA2024-WNZ. The heterogeneous microstructure evolution lowers the GC resistance of global WNZ, causing the severest GC at WNZ-bottom with lowest resistance. The GC and intergranular corrosion synergistically promote the dissolution process. This work provides an insight on GC of dissimilar joint from microstructural heterogeneity.

Microstructure and mechanical properties in dissimilar friction stir welding between aluminum 1050 and 316L stainless steel

Microstructure and mechanical properties in dissimilar friction stir welding between aluminum 1050 and 316L stainless steel

Effects of Zr interlayer on microstructure, mechanical property and corrosion behavior of Al/Mg dissimilar friction stir welding lap joints

Effects of Zr interlayer on microstructure, mechanical property and corrosion behavior of Al/Mg dissimilar friction stir welding lap joints

Effect of number of tool shoulders on the quality of steel to magnesium alloy dissimilar friction stir welds

Effect of number of tool shoulders on the quality of steel to magnesium alloy dissimilar friction stir welds

Experimental investigation of the effect of induction preheating on the microstructure evolution and corrosion behaviour of dissimilar FSW (IN718 and SS316L) joints

The present work investigates the microstructure and electrochemical behaviour of the joints formed with and without induction-assisted friction stir welds (FSW) between SS316L and Inconel 718. For this purpose, conventional and induction preheating assisted friction stir welding (I-FSW) was carried out at a rotational speed of 300 rpm and traverse speed of 140 mm/min with 300 °C preheating. The microstructure and phases of the nugget zone were analyzed. The corrosion behaviour of the welded joint and the base metal was investigated in 1 M HCl solution and 3.5 wt% NaCl solution using immersion test and electrochemical techniques. The results show that the induction preheated friction stir welding process produces defect-free joints than the conventional FSW with little increased grain size. Intermetallic compounds (IMCs) at the interface of the nugget zone were not detected due to insufficient heat input. The corrosion result revealed that the corrosion resistance of the I-FSW weld joint was better than the FSW weld joint, and it was lowest in the case of base SS316L, which was confirmed with the immersion test, potentiodynamic polarization test (PDP), and electrochemical impedance spectroscopy (EIS). The presence of blocky carbide particle M23C6 was responsible for the pitting corrosion in the steel region.

Simulation of dissimilar friction stir welding of AA7075 and AA5083 aluminium alloys using Coupled Eulerian–Lagrangian approach

Temperature, strain and material flow during the friction stir welding (FSW) process are factors that determine the quality of the resulting joint. Examining these features by experimental methods is very difficult, so the numerical method is developed. This paper focuses on simulating the FSW of AA5083 to AA7075 aluminium alloys. At first, in order to investigate the materials mixing and also to study the microstructural properties and hardness of the samples, the samples were welded using a milling machine. Then, according to the used parameters, the process was modelled. For this reason, a Coupled Eulerian–Lagrangian (CEL) was employed to estimate thermal, strain and material mixing. Comparing the stir zone (SZ) of the joint produced and predicted by simulation revealed that the CEL approach has well-determined the material mixing in the SZ. The experimental results show that the highest hardness value is 112 HV in the thermo-mechanically affected zone of AA7075 alloy. The numerical results indicate an unequal strain distribution along the weld centre line due to the lower strength of AA5083 and a ‘positive’ interaction between the tool welding and rotational speed on the advancing side.

Multi-phase modelling of heat and mass transfer during Ti/Al dissimilar friction stir welding process

Friction stir welding (FSW) has the capacity to join the Al/Ti dissimilar structures with superior mechanical properties. The microstructures and mechanical characteristics of Al/Ti dissimilar FSW joints are determined by the heat and mass transfer during the welding process. However, a quantitative study of the Al/Ti dissimilar FSW process is lacking. Therefore, using the computational fluid dynamics (CFD) and volume of fluid (VOF) approach, a multi-phase model was constructed for quantitatively analyzing the heat and mass transfer behaviour in dissimilar FSW of TC4 titanium alloy and AA2024-T4 aluminium alloy. The mixed material was treated as a functionally graded material (FGM) to compute the thermophysical characteristics at the weld nugget zone (WNZ). Due to the vast disparity in the thermophysical characteristics of aluminium and titanium alloy, the temperature field in Al/Ti dissimilar FSW was severely asymmetric. The temperature of titanium alloy on the advancing side (AS) was higher than that of aluminium alloy on the retreating side (RS) at the same distance from the tool centre line near the tool shoulder, but it was lower than that of aluminium alloy on the RS without the influence of the shoulder. Due to the high flow stress of titanium alloy, plastic material flow mostly occurred on the RS of aluminium alloy in the Al/Ti dissimilar FSW, with its percentage exceeding 80 %. This model was validated by experiment results.

Similar and dissimilar lap friction stir welding of titanium alloys: on the elimination of the hook defect

Similar and dissimilar lap friction stir welding of titanium alloys: on the elimination of the hook defect

Effect of Tool Pin Geometries on Weld Quality of Al/Cu Dissimilar Friction Stir Welding

Effect of Tool Pin Geometries on Weld Quality of Al/Cu Dissimilar Friction Stir Welding

Favorable property integration in high entropy alloys via dissimilar friction stir welding: A case study using Al0.3CoCrFeNi and Fe38.5Co20Mn20Cr15Si5Cu1.5 HEAs

The advent of high entropy alloys (HEAs) enabled fine-tuning of the alloy composition from the vast compositional space to develop solid-solution alloys having good physical and mechanical properties. Each HEA composition is the culmination of careful alloy design strategy aimed at a specific property intended for a specific application that is achieved by microstructural alteration and/or activation of deformation mechanisms. Methods to integrate the favorable properties pertaining to each HEA potentially benefit alloy selection for structural applications. In this study, dissimilar friction stir welding (FSW) was performed using Al0.3CoCrFeNi HEA and Fe38.5Co20Mn20Cr15Si5Cu1.5 TRIP HEA to integrate the beneficial mechanical properties of both HEAs. Unlike fusion welding methods that lead to a weaker weld zone, dissimilar FSW of the HEAs resulted in a refined microstructure in the stir zone (SZ) with enhanced mechanical performance compared to both base materials and enabled promising property integration. Improved and integrated mechanical property achieved in SZ was correlated to the microstructure, existing recrystallization mechanisms, and active deformation mechanisms in both alloys.

Prediction of various defects and material flow behavior during dissimilar FSW of DH36 shipbuilding steel and marine grade AA5083 using FE-based CEL approach

Dissimilar friction stir welding (FSW) of steel-Al is a very tedious job. Inappropriate welding process parameters can lead to the initiation of inevitable defects associated with dissimilar FSW processes. These can be presented as tunnel defects, void generation, excessive flash formation, and other surface irregularities. Using conventional experimental trials makes it usually challenging to identify such defects. This research adopted an Abaqus/Explicit® framework utilizing a 3D thermo-mechanical based coupled Eulerian-Lagrangian (CEL) methodology. In order to predict commonly observed defects in the FSW process, the proposed FEM uses the volume of fluid approach. By monitoring the material flow into and out of the computational/void domain, the suggested framework has made it feasible to predict surface, sub-surface, and volumetric defects. Defect formation is studied at a constant tool rotation speed of 875 rpm, welding speed of 90 mm min−1, and tilt angle of 0°. Tilt angles of 0° caused welding joints with a small tunnel defect. Thermal history, axial force variation, and material flow behavior are all strongly aligned with the principle of defect generation. An experimental trial has been conducted to validate the proposed finite element model. The previous analysis found that the average axial force closely matches the welding-related experimental findings with a percentage error of 7.85%. While a proportion error of approximately ∼0.57% was found between the compared numerical and experimental diameters of the pin end-hole defect. Furthermore, the proposed model accurately predicted the process of material flow along the thickness direction of the workpiece. It was seen that the stress generated at the root of the flashes reached a higher value ranging between 485.6 and 582.7 MPa. Finally, a good agreement between the numerical results and the experimental trial was established, showing the robustness of the developed computational FEM technique.

Strain and damage analysis using high resolution digital image correlation in the stir zone of an AA6061-AA7075 dissimilar friction stir weld

Strain and damage analysis using high resolution digital image correlation in the stir zone of an AA6061-AA7075 dissimilar friction stir weld

Unravelling the ultrasonic effect on residual stress and microstructure in dissimilar ultrasonic-assisted friction stir welding of Al/Mg alloys

An in-depth knowledge and understanding of residual stress in dissimilar ultrasonic vibration-assisted friction stir welding (UVaFSW) are crucial for the performance evaluation of multimaterial structure designs; however, extensive research is still lacking. The present study evaluated the residual stress of dissimilar aluminium (Al)/magnesium (Mg) alloy joints produced by traditional FSW and UVaFSW to elucidate the ultrasonic effect mechanism with the aid of process simulation and microstructural evaluation. The weld surficial residual stress measured by X-ray diffraction (XRD) using the cos α method indicated the generation of predominantly compressive stress in UVaFSW welds. In agreement with the XRD measurements, the stress maps evaluated using the contour method (CM) exhibited an expanded compressive stress region and a mitigated tensile stress region in the UVaFSW welds. The Al/Mg interfacial mismatch of thermal expansion led to a tensile stress state on the Mg side and a compressive stress state on the Al side near the Al/Mg interface. The maximum compressive stress in the UVaFSW weld was ∼100 MPa higher than that in the FSW weld. The ultrasonic effect proficiently reduced the layer thicknesses of the intermetallic compounds (IMCs), promoting grain recrystallisation behaviour due to improved material transfer and mixing. Consequently, more homogeneous hardness distributions and improved tensile properties were formed in UVaFSW welds. However, ultrasonic vibration had an insignificant effect on the density of geometrically necessary dislocations and stored strain energy, indicating limited effects on microscopic residual stress in the studied condition. The ultrasonic vibration was found to positively mitigate residual tensile stresses and macroscopic distortion by increasing the temperature and encouraging material mixing within the stirred zone, as well as enhancing the stress interaction of the Al/Mg interface related to thinner IMCs. The UVaFSW has considerable potential to in-process co-optimise residual stress and microstructure for dissimilar Al/Mg welds.

Appraising Tool Wear during Secondary Heating Assisted Dissimilar Friction Stir Welding between 6061 and 7075 Aluminium Alloys

Appraising Tool Wear during Secondary Heating Assisted Dissimilar Friction Stir Welding between 6061 and 7075 Aluminium Alloys

Attributes of intergranular corrosion in AA6061-AA7075 double sided friction stir weld

The present study aims to observe the distinguishable progression of intergranular corrosion (IGC) in dissimilar AA6061-AA7075 double-sided friction stir welds (DSFSW) with and without employing secondary heating. Transverse weld specimen sectioned along the weld line, to separate advancing and retreating side, are electrochemically corroded. Secondary heating helps in impeding the most accelerated corrosion rate dominated over the AA7075 region by approximately 50%. The double stirred region remains least susceptible to corrosion due to the dissolution and break down of precipitates. The degree of homogenization during stirring of dissimilar alloy controls the degree of material depletion during corrosion, making intercalated structure unfavourable in terms of corrosion. IGC is found more aggressive in AA7075 structurally intercalated with AA6061 in stir zone. The coarse grain, wider precipitate free zones and continuity of the precipitates along grain boundary (GB) are interpreted as most influential factors. Additional/secondary heating resulted into retardation of IGC within the AA7075 but resulted continuous IGC along the GBs of AA6061. Low angle GBs appears more resistive against IGC as they allow the formation of lean precipitates on contrary to high angle GBs. Secondary heating boosts breakdown and dissolution of corrosion sensitive secondary phase particles reducing the intergranular corrosion tendency.

Optimization of dissimilar AA5052-H32 and AA5083-H111 aluminium FSW joints with scandium interfacial layer

ABSTRACT This study examines the influence of friction stir welding (FSW) on the mechanical and metallurgical characteristics of scandium interfacial layered dissimilar AA5052-H32 and AA5083-H111 aluminium alloy FSW joints. The ultimate tensile strength and microhardness are found to be most affected by the welding speed, tool rotating speed, and axial load. During experimental trials based on the central composite design, the input welding parameters were optimized using the response surface approach. Peak ultimate tensile strength (234.07 MPa) and microhardness (95 HV) were measured for ideal parameters of tool rotation speed = 1000 rpm, welding speed = 28 mm/min, and axial load = 10 kN. The presence of scandium interfacial layer and optimized parameters enhanced the mechanical properties of the joint and generated a fine-grained microstructure. The current work is unique in that it uses this alloy combination to do parametric optimization of the scandium interfacial layered dissimilar aluminium alloy FSW joint.

Fatigue life improvement of similar and dissimilar aluminum friction stir welds by deep rolling

At the moment, high production costs prevent the friction stir welding (FSW) process from further industrial applications even if comparable high fatigue strength of the joints can be reached. Higher welding speed may reduce the production costs but decrease the fatigue strength of the manufactured FSW joints. A potential solution is a mechanical post weld treatment directly after welding to increase the fatigue strength of the FSW joint again. In this study, hydrostatic deep rolling was applied for fatigue strength improvement of similar and dissimilar FSW joints made of EN AW 5083 and EN AW 6082 alloys manufactured with different welding speed. Additionally, the fatigue strength was directly compared to conventional joints manufactured by metal inert gas (MIG) welding and to base material specimen made of EN AW 5083. The surface state in as-welded condition was characterized by surface roughness and residual stress measurements. Fatigue tests were performed to quantify the fatigue strength of the FSW joints. Similar compressive residual stresses were determined after deep rolling for similar and dissimilar joints. No fatigue life improvement was determined for deep-rolled similar joints made of EN AW 5083. However, in this condition, the fatigue life of the specimen was within the range of the base material. Thus, significant lower fatigue life and a high fatigue life improvement by deep rolling were reached for dissimilar joints. An increase of the welding speed from 300 to 800 mm/min strongly decreased the fatigue strength of dissimilar welded joints in the investigated case.

Effect of the offset between double-pass on texture and tensile properties of dissimilar friction stir welded joints of ZK60 and Mg-4.6Al-1.2Sn-0.7Zn alloys

• The double-pass with an offset can improve the joining efficiency of the FSW of Mg. • The double-pass with an offset can attenuate the boundary mutations of the weld. • The offset between two passes increased the non-uniform distribution of texture. • The best welding effect is achieved when the offset between two passes is 1 mm. A double-pass with an offset between the two passes was attempted for the dissimilar friction stir welding of magnesium alloys, which can significantly improve the tensile properties of the welded joints compared with a single-pass. However, the increase in offset exacerbated the inhomogeneous distribution of the texture, which was detrimental to the mechanical properties of the joints. When the offset was approximately 1 mm, the double-pass welded joint obtained a tensile strength of 250.1 MPa, an elongation of 8.2%, and a welding efficiency of 92%, which is about a 10% improvement in welding efficiency over a single-pass joint.

Dissimilar Friction Stir Welding of AA2519 and AA5182.

In this study, the friction-stir welding (FSW) technique was successfully applied for joining of AA2519 to AA5181 alloy. Microstructure and mechanical properties of dissimilar FSW joints were investigated by optical microscopy, microhardness, and tensile testing. The deformation behaviour of the welded joints was elucidated via the digital image correlation technique. After welding, the ultimate tensile strength of joints was ~300 MPa and ductility was ~16%. The microhardness values observed at the stir zone were higher than those in the base material AA5182. The produced welds demonstrate nearly 100% (based on AA5182) joint efficiency.

Investigation of material flow, microstructure evolution, and texture development in dissimilar friction stir welding of Al6061 to Ti6Al4V

Aluminium -Titanium dissimilar welds are widely used in defence and aerospace industries. Welding of Al to Ti is highly challenging due to the wide difference in thermo-mechanical properties. One of the most promising techniques for producing dissimilar welds is friction stir welding. In the present study, material flow, texture, and microstructural evolution of Ti-6Al-4 V and Al6061 dissimilar friction stir welded joints are elucidated at the Ti interface and centre of the stir zone (CSZ). Material flow pattern reveals the spread of fragments of Ti particles of around 80.3% at the interface and about 23% at the CSZ. The dispersion of Ti fragments in the stir zone resulted in better strength and hardness values of around 256 MPa and 345 HV, respectively, with failure of the specimens in the heat-affected zone of Al6061 side. The interface microstructure at Ti reveals plenty of equiaxed and recrystallized grains. The strengthening mechanism at the Ti interface is due to the dynamic recovery driven by adiabatic shear bands (ASBs) and twin-induced deformation. The electron backscattered diffraction results revealed the presence of 91% and 77% of strain-free recrystallized grains at the Ti interface and CSZ, respectively. The strong texture components of S {123} < 346 > in Al and D {0001} < 112̅0 > in Ti were also observed.