Dissimilar Aluminium Alloy Joints Research Articles

Optimization and Analysis of Refill Friction Stir Spot Welding (RFSSW) Parameters of Dissimilar Aluminum Alloy Joints by FE and ANN Methods

The quality of the refill friction stir spot welding (RFSSW) process is heavily dependent on the selected welding parameters that influence the resultant joint characteristics. Thermomechanical phenomena integral to the process were investigated using finite element (FE) analysis on two dissimilar materials. This FE analysis was subsequently validated through controlled experiments to ensure reliability. An artificial neural network (ANN) was employed to create a neural model based on an experimental setup involving 120 different sets of welding parameters. The parameters adjusted in the experimental plan included pin penetration depth, rotational speed, retention time, and positioning relative to material hardness. To assess the neural model’s accuracy, outputs such as maximum temperature and normal stress at the end of the welding process were analyzed and validated by six data sets selected for their uniform distribution across the training domain.

Effect of swinging laser on porosity, microstructure, and mechanical properties of laser welded aluminum alloy joints with different lap forms

Oscillating and conventional linear laser welding were conducted to enhance the bonding strength of dissimilar aluminum alloys. The effect of lap joint configuration on porosity, microstructure, and mechanical properties of laser-welded dissimilar aluminum alloy joints was investigated. It was found that the solidification rate of the melt pool was the dominant factor in the difference in porosity for oscillating laser-welded joints with different lap joint configurations. The main precipitated phase in welds with different lap joint configurations was eutectic Si, and the proportion of eutectic Si was higher in oscillating laser welds than in linear laser welds. The elemental distribution in oscillating laser welds was more uniform. The strengthening mechanism for tensile shear strength of oscillating laser welded lap joints was analyzed. The improved tensile shear strength and elongation were attributed to the reduced porosity and solid solution strengthening for the oscillating laser welding. The tensile strengths of the two lap types of oscillating laser welded joints increased by 25.1 MPa and 34.5 MPa, and the elongation increased by 0.7% and 4.5%.

Fatigue life evaluation of laser welded lap joints of dissimilar aluminum alloys

Abstract Constant amplitude fatigue tests were conducted on 6061/7075 dissimilar aluminum alloy laser welded lap specimens, as well as weld line cross-section hardness measurements. The fatigue test results show that the specimens exhibit multiple fracture modes that exit near the weld seam. The microhardness data on weld line cross-section from 7075 side to 6061 side display a sharp change and the softening phenomenon is serious. The hardness variation in heat affected zone of laser welding is very shallow, and its hardness is close to that of the base material. It was found that there are slag inclusions and pores in the weld seam when observing the fatigue fracture surface using SEM, and a small amount of secondary cracks were generated. However, stress concentration plays a dominant role in causing specimen fracture under fatigue loading, rather than welding defects. Defective specimens are found to have higher fatigue strength. The fatigue life prediction results obtained by the notch stress method and the hot spot stress method are both conservative and fall within two factor lines. The hot spot stress method has relatively higher accuracy for life prediction. The accuracy of both methods in predicting life is influenced by the location of the fracture.

Microstructure and Mechanical Properties of Electrically Assisted Brazing Joints of Dissimilar Aluminum and Steel Alloys

The microstructure and mechanical properties of electrically assisted brazing (EA-brazing) joints of aluminum alloy 6061-t6 (AA6061-t6) and S45C steel are experimentally investigated. During the EA-brazing process, an electric current is directly applied to the cylindrical specimen assembly (S45C and AA6061-t6) and fillers of 88% Al and 12% Si (in the middle of the specimen assembly). The temperature of the specimen assembly rises rapidly to the melting point of the filler and remains nearly constant for a period of time using a pulsed electric current. Two types of EA-brazing joints are fabricated, namely Joint-0s (no temperature holding time) and Joint-12s (12 s temperature holding time). The characteristics of the intermetallic compounds (IMCs) formed at the EA-brazing joint interface are analyzed using scanning electron microscopy and energy dispersive spectrometer. Compared to Joint-0s, the Fe-rich IMCs (FeAl) are observed at the interface of Joint-12s due to the 12 s temperature holding time. In addition, the microstructural analysis shows that the thickness of the diffusion layer increases with increasing temperature holding time. The mechanical properties of the EA-brazing joints are evaluated using bending tests. The results of the mechanical test show that the strength of Joint-12s is higher than that of Joint-0s.

Effects of filler on the microstructure and corrosion of similar and dissimilar gas inert tungsten arc welding aluminum alloys joints

Welding of dissimilar aluminum alloys has been widely used in many industrial applications. However, the selection of filler type still attracts significant interest in the welding research area. The present work concerns the effect of filler metal on the microstructure and corrosion of weld joints of dissimilar aluminum alloys. AA 5083 and AA 6082 alloys were welded by tungsten inert gas welding (GTAW) using filler metals ER 4043 and ER 5356. The microstructure observations and the corrosion test of the weld joints were carried out. Solidification cracks were observed in the ER 4043 weld zone, whereas defect-free joints were obtained using a mix filler welding process. A galvanic corrosion was observed on the boundary between the filler rod ER 4043 weld zone and AA 5083 base alloy. From the corrosion standpoint of view, the using of ER 4043 electrodes is not preferred for welding 5000 series aluminum alloys, whereas ER 5356 filler electrode is more favorable than ER 4043 filler electrode either for dissimilar welding of AA 5083 and AA 6082 alloys or individual welding of both aluminum alloys. No galvanic corrosion is observed between ER 4043 fillers and AA 6082 base alloy.

Multi-response Optimization of Friction Stir Welded Reinforced Joints of Dissimilar Aluminum Alloys

Multi-response Optimization of Friction Stir Welded Reinforced Joints of Dissimilar Aluminum Alloys

Microstructure and mechanical behavior of similar and dissimilar AA2114 and AA7075 aluminium alloy joints using fusion welds

Joining of aluminium and its alloys are always a major challenge to welding community because of high thermal conductivity, coefficient of linear expansion, affinity to combine with oxygen and sensitive to hot cracking. Ample of researches carried out to address above issues. The selected investigation aimed at one such attempt to combine AA2114 and AA 7075(AA2XXX and AA7XXX series promises a lot in aircraft applications) in all possible ways i.e. similar and dissimilar by adopting TIG (Tungsten Inert Gas) and CMT (Cold Metal Transfer) welding. After series of trials, all the combinations welded successfully and tensile specimen as per ASTM E8 machined. While performing mechanical testing, all specimens failed along the interface of weld zone and AA2114 side irrespective of TIG/ CMT dissimilar welding. This is accounted to softening in the heat affected zone of selected heat treated alloys i.e. AA2114 and AA7075. Among all the fabricated weld joints AA 2114-AA7075 specimen showed highest ultimate tensile strength of 247 MPa using filler ER 4043 alloy with CMT welding. Yielding of above outcome may be due to segregation of alloying elements (acts barrier to dislocation motion) and low concentrated heat input (favoring maximum extent of finer dendritic equiaxed grains).XRD-report revealed the presence of Zn, Cu, Mg elements in the intermetallic to have strength in CMT dissimilar CMT weldment. SEM analysis report on dissimilar joints of both TIG and CMT exemplifies the presence both dimples and flakes, which led to the ductile–brittle mixed mode nature of failure.

Investigation of the Microstructure and Mechanical Properties in Friction Stir Welded Dissimilar Aluminium Alloy Joints via Sampling Direction

This research study investigates the influence of sampling direction on the microstructure and mechanical properties of dissimilar joints formed by friction stir welding (FSW). The specimens were cut in two directions: perpendicular (transverse) and parallel (longitudinal) to the FSW joint. The tests conducted included X-ray diffraction (XRD), macrostructure, microstructure, tensile, microhardness, and fractography analysis. Different phases were noted in the XRD patterns and explained, with the aluminum phase being the dominating one. The results further showed that the transverse dissimilar joint exhibited higher microhardness compared to the longitudinal dissimilar joint, which is consistent with the respective grain sizes. Moreover, the ultimate tensile strength of the longitudinal joint exceeded that of the transverse joints, showing a substantial 47% increase. Similarly, the elongation of the joints followed a similar trend, with the longitudinal joint displaying a significant 41% increase in elongation compared to the transverse joint. Fractographic analysis revealed ductile fracture behaviour in all joints.

Development of mechanical property prediction model and optimization for dissimilar aluminum alloy joints with the friction stir welding (FSW) process

Friction stir welding (FSW) is a solid-state joining process used to weld dissimilar aluminum alloys with varying material properties and compositions. Unlike traditional welding methods, FSW does not involve melting the materials being welded but instead uses a rotating tool to heat and stir the materials until they are in a plastic state. The process results in a welded joint with high strength, excellent ductility, and minimal distortion, making it a popular choice in various industries, including aerospace, automotive, and marine. AA6061-T6 (Mg-Si) and AA7075 (Al-Zn-Mg-Cu) aluminum alloys are one of the most popular grades of aluminum alloys used in current manufacturing industries, such as aerospace and automotive, joined by the Friction Stir Welding Process (FSW) technique. Taguchi orthogonal array (L9) experimental design was applied to reduce the number of insignificant factors in the process. First, the study determines three welding factors: rotation speed, travel speed, and pin eccentricity. Investigations found that travel speeds significantly on tensile strength (Ts) and elongation ( %El), but the rotational speed and tool eccentricity did not affect Ts and %El. Furthermore, considering the fabricated parameters on the hardness (HV) of the joint, it was found that all factors unaffected the HV of the joint zone at a 95 % confidence level. Next, examine the microstructure; Mg2Al3 and Al2O3 intermetallic compounds were found in the weld. Therefore, investigating the crystallite size found that welding significantly affects the crystallite size. Finally, consider the fracture surface, experimental condition A2B1C2 (optimal parameter), which is the parameter with the highest tensile strength having dimple fracture characteristics. On the other hand, the welding condition A1B3C3, the parameter with the lowest tensile strength, Small and fine dimple fracture with cleavage fracture. Because the material is highly ductile and can undergo large deformations before it is damaged. On the other hand, materials with low tensile strength exhibiting cleavage fracture indicate that the materials are brittle and can break easily under stress

Impact of ultrasonic vibration power and tool pin profile on mechanical and microstructural behaviour of friction stir welded dissimilar aluminium alloy joints

PurposeThe purpose of this paper is to investigate the impact of ultrasonic vibration (UV) and tool pin profile on mechanical properties and microstructural behaviour of AA7075-T651 and AA6061-T6 joints was analysed.Design/methodology/approachThe joints were fabricated using three different tool pin profiles such as cylindrical, square and triangle. For each tool pin profile, two different UV powers of 1.5 kW and 2 kW were used.FindingsOn both the advancing and retreating sides of the weld, the thermo-mechanically affected zone has the lowest microhardness. In all joints, the tensile fracture locations match to the minimum hardness values. Field emission scanning electron microscope fractography of tensile tested specimens reveals heterogeneous modes of brittle, shear and ductile fracture. Three-point bending analysis was performed to determine the ductility and soundness of the weld joint. The acoustic softening effect of UV, as well as the static and dynamic ratio of tool pin profile, plays an important role in determining the material flow and mechanical behaviour of the joint.Practical implicationsDissimilar aluminium joining fascinates many applications like aircraft, aerospace, automobiles, ship building and electronics, where fusion welding is a very intricate process because of the deviation in its physical and chemical properties.Originality/valueFrom this study investigation, it is found that the square pin profiled tool with 2 kW UV power produces metallurgical defect-free and mechanically sound weld with maximum tensile strength, hardness and bending load of 297 MPa, 151HV and 3.82 kN, respectively.

Studies on Effect of Tool Pin Profiles and Welding Parameters on the Friction Stir Welding of Dissimilar Aluminium Alloys AA5052 & AA6063

Abstract: Friction stir welding (FSW) is a solid-state joining process that uses the frictional heat generated by the rotating tool to soften the metals to form the joint. It is an effective technique for joining dissimilar aluminum alloys and finds its application in various fields such as aerospace and automotive industries. FSW process is energy efficient and environment friendly process. This FSW can produce joints with higher mechanical and metallurgical properties. Formerly, FSW was adopted for low melting metals like aluminum alloys. The various FSW parameters play a vital role in determining the quality of the welded joint. The parameters included in the study of different tool pin profiles (circular, pentagon and taper). FEA analysis will be performed for friction stir welding of Aluminum alloy 5052 and AA6063 at different tool pin profiles using ANSYS. This paper mainly focuses on studying the effect of different tool pin profiles on the microstructure and mechanical properties of the dissimilar AA5052 and AA6063 aluminum alloy joints. The weld quality characteristics like microstructure, micro-hardness, and tensile properties of the joints are analyzed and presented for three different tool pin profiles. It is observed from the result that the joint fabricated using three different tool pin profiles exhibits the better mechanical properties when compared to other joints. Index Terms: Friction stir welding, Aluminium alloys, AA5052, AA6063, Dissimilar welding.

Effects of interlayer metal on microstructures and mechanical properties of friction stir lap welded dissimilar joints of magnesium and aluminum alloys

The content of intermetallic compounds (IMCs) in friction stir lap welded (FSLW) dissimilar joints of Mg and Al alloys could be reduced by the addition of interlayer metal to improve the mechanical properties of the joints, while the underlying mechanism is still unclear. In this study, Cu and Ni powders are added as the interlayer materials into the FSLW joints of AZ31 Mg alloy and Al–Zn–Cu–Mg alloy, respectively. The types, sizes, and distributions of IMCs have been characterized, and the shear properties of the joints have been evaluated. Moreover, the mechanism underlying the influence of the interlayer metals on the evolution of IMCs in the joints and the effect of IMCs on the shear properties of the joints have been studied. The results showed that the order of phase formation in the joint without interlayer was Al12Mg17, Al3Mg2, MgZn2, CuMg2, Al2Cu, while the order of phase formation in the joint with added Cu interlayer was Al2Cu, CuMg2, AlCu, Al12Mg17, Al3Mg2, Cu5Zn8, and that in the joint with added Ni interlayer was Mg2Ni, Al3Ni, Al3Ni2, MgNi2, AlNi, Al12Mg17, Al3Mg2, MgZn2, Ni3Zn22, NiZn, Al2Cu. Due to the formed physical barrier and the mechanism of phase formation, the addition of interlayer metal effectively inhibited the formation of a Mg–Al phase. The bonding strengths between Mg–Cu, Al–Cu, Al–Ni, and Mg–Ni phases and matrix were higher than that between Mg–Al phase and matrix, which improved the shear properties of the joints with Cu and Ni interlayers.

Effect of friction time on tensile strength and metallurgical properties of friction welded dissimilar aluminum alloy joints

Abstract Dissimilar (AA6061 & AA7075-T6) friction welded aluminum joints were taken into the investigation to correlate the influences of friction time on tensile and metallurgical properties. The dissimilar metals were welded by varying the friction time from 2 s to 6 s with the following constant parameters: a rotating speed of 1200 rpm, friction pressure of 35 MPa, upset pressure of 35 MPa, and upset time of 3 s. The higher friction time during joint fabrication needs to be selected to attain good metallurgical bonding between rubbing surfaces. The highest tensile strength of 228 MPa was attained when the friction time was given as 4 s. Furthermore, the increase in friction time widened the width and reduced the hardness of the heat affected zone on the AA6061 side where joint failure occurred. Finally, the metallurgical features of the dissimilar specimens were characterized using optical microscopy, scanning electron microscopy, and X-ray diffraction. Other details related to the characterization and results of the testing were recounted.

Influence of tool pin profiles on the filler added friction stir spot welded dissimilar aluminium alloy joints

Dissimilar metals are pretty challenging to attain enhanced mechanical properties in the conventional friction stir spot welding (FSSW) process. In this research, a new filler added friction stir spot welding (FAFSSW) process is adopted for welding dissimilar aluminium alloys of AA5052 with AA6061 by using five different tapered tool pins to enhance the mechanical and metallurgical properties of the joints. Magnesium (Mg) powder with 4.5 mg in volume fraction is considered filler material to fabricate the joints. Mechanical properties of the spot weldments like tensile shear strength test, microhardness test, and metallurgical characterizations like microstructure analysis were carried out for FAFSSW joints. The results show that a tool pin profile with 5 mm upper diameter, 2 mm lower diameter and a pin length of 1.2 mm produce a sound joint with 202.85 MPa tensile shear strength and 119.9 HV microhardness. The FAFSSW joint shows 34% higher strength than the normal FSSW joints. The microstructure analysis indicates that the Mg filler mixes well in the weld zone, and a fine grain structure is gained without any defects.

Optimization and Mechanical Characterization of AA5083 and AA7075 Dissimilar Aluminium Alloy Joints Produced by Friction Stir Welding

In this research work the aluminium alloys including AA7075 and AA5083 are combined with friction stir welding method. This contrasts with factors such as alloy segregation, hot cracking and porosity which result from fusion welding process in the welded area. In order to generate high quality joint of aluminium alloy, friction-stir welding (FSW) an assuring welding method is followed. To achieve the determined strength, an entire control over the relevant process is needed to increase the tensile vitality. The welding factors like welding speed (WS), axial force (AF) and rotational speed (RS) are examined for optimisation. In order to measure the impact of the factors on tensile strength of FS welded joints, Taguchi L9 orthogonal array technique is employed. The amount of involvement of these factors on weld quality is determined by means of analysis of variance (ANOVA). The utmost ultimate tensile strength (UTS) attained for AA7075 and AA5083 joint is 256MPa. ANOVA results show that the quality-wise effectiveness of the weld as welding speed (5.48percent), axial force (15.18percent), then the rotational speed (79.32percent). This is due to the presence of fine equiaxed grains in the microstructures of the stir zones at different FS welding circumstances. However, a decrease in the grain size of the process zone is observed when the frictional heat flow is decreased while friction-stir welding.

The Impact of Material Positioning Towards the Friction Stir Welded Dissimilar Aluminium Alloy Joints

Background: Friction stir welding is an advanced process that could be used to join dissimilar materials and alloys. However, there are some areas that require some further analysis. This involves the impact of the material positioning on various dissimilar joints. Objective: The purpose of this paper is to investigate the influence of material positioning on the microstructure and the mechanical properties of AA8011/AA6082 and AA6082/AA8011 dissimilar joints. Methods: The materials used in this study were the 6mm thick AA8011 and AA6082-T6 plates. The welding conditions include a tool rotational speed of 1100 rpm, and a traverse speed of 60 mm/min. Microstructural analysis, Vickers hardness and tensile tests were conducted in order to be able to draw a comparison between the respective joints. Results: The joints (AA8011/AA6082 and AA6082/AA8011) both experienced dynamic recrystallization. The positioning of the stronger strength alloy on the advancing side resulted in finer microstructural grains compared to when the lower strength alloy was positioned on the advancing side. The maximum stir zone hardness of 75 HV was obtained on the AA8011/AA6082 dissimilar joint, while the AA6082/AA8011 had a minimum hardness of 68 HV. Both hardness values were lower than the AA6082 hardness but greater than that of the AA8011. The positioning of AA6082 on the advancing side resulted in higher ultimate tensile strength than when AA8011 was on the advancing side. The AA6082/AA8011 joint was found to be more ductile in comparison to the AA8011/AA6082 joint. The fracture surface morphology of the post tensile specimens also revealed a ductile failure morphology. Conclusion: Placing the stronger strength alloy on the advancing side resulted in sound overall results of the tests conducted.

Experimental investigation on fatigue crack initiation and propagation mechanism of friction stir lap welded dissimilar joints of magnesium and aluminum alloys

At present, the effect of the microstructure of friction stir lap welded (FSLW) dissimilar joints of Mg and Al alloys on fatigue crack initiation and propagation is not clear. In this article, the effects of the microstructure of FSLW dissimilar joints of AZ31 Mg and Al–Zn–Cu–Mg alloys are studied. The grain orientations of the crack initiation and propagation region were characterized by electron backscattering diffraction analysis. And the models for fatigue crack propagation in the different grain orientations were established. Based on the above experimental results, the initiation mechanisms of fatigue cracks were clarified, and the effects of grain orientations on crack propagation were revealed. The results showed that the crack initiation was caused by the simultaneous activation of the (0002, 21¯1¯0] basal slip and twinning in various directions by fatigue loading. The direction of crack propagation was dominated by the (0002)[2¯110] basal slip with (1¯012)[1¯011¯] twinning adjusting in the crack propagation zone. The cyclic effect of concentration and release of stress on the activation and termination of twins was the main reason for the zigzag path of crack propagation.

Sustainable Processing of Dissimilar Aluminium Alloy Joints by Friction Stir Welding

Friction stir welding is one of the unique solid state welding technique that is fast gaining importance because of its excellent properties pertaining to the strength, wear, hardness and better joining capabilities. The friction stir welding technique is effectively used in this research to join 5 mm thick dissimilar aluminium alloys of AA 7075 and AA 5052 grade. The friction stir welding joints are obtained by using three different tool profiles viz., straight cylinder, taper cylinder, and straight triangular at a speed of 800, 1000, 1200 rpm and a feed rate of 100, 120, 140 mm/min. The experiments are designed based on L9 orthogonal array considering Taguchi techniques. From the experimental results, the process methodology is validated and the outcomes of the experiment are considered for fabrication of strong joints. The design and optimization of the process has led to better process control and thereby extended its scope for the use of the optimized process parameters for joining dissimilar aluminium alloys in real time engineering applications with sustained methodologies involving reduced dwell time and optimized friction forces and torque during the friction stir welding of dissimilar aluminium alloys.

Influence of D/d ratio on stir zone formation and properties of friction stir welded dissimilar joints of AA5086 and AA6061 aluminum alloys

A well-known method known as Friction stir welding (FSW) is used for combining materials that are distinct from each other. In FSW, a profiled spinning shoulder shifts between sheets of the sections that are to be connected. Heat is produced due to the friction between the base and the tool shoulder when the tool is turning along the weld line. In contrast to fusion welding processes, the heat produced is lower. In these works, the effect of macro/microstructures characterization and the tensile characteristics of the dissimilar AA5086 and AA606I aluminum alloys on the ratio of tool shoulder diameter and tool pin diameter (D/d) used in the FSW were explored. This study shows the superior tensile characteristics on welding components in contrast to the counters made of the sealing units made using a tool profile of threaded cylinders, a 1 ° tool tilting angle, tool rotation speed of 1100 rpm, the welding speed of 22 mm/min and the shoulder diameter is 21 mm. Further, the joints fabricated using threaded cylinder tool profile exhibited superior macro structure compared to its counter parts.

Characterization and Optimization of Flat Friction Stir Spot Welding of Triple Sheet Dissimilar Aluminium Alloy Joints

The method of flat friction stir spot welding (FFSSW) was used to investigate the tensile behavior of three thin dissimilar aluminium alloys (Two sheets of AA6082-T6 and one sheet of AA6061-T6). Tool with probe and a probe less tool is used in this two-step process of joining. Experiments were conducted at various tool tilt angles (TTA), tool rotational speeds (TRS), dwell time (DT) and Tool plunge depths (TPD). The quality welds were produced at optimized process parameters (TTA 20, TRS 2125 rpm, DT 15 s and TPD 0.1 mm). Elimination of protuberance and reduction of keyhole in the joint is achieved for improving bonding length. Micrographs of joints were examined using optical microscopy and scanning electron microscopy (SEM). The complete bonding with finer grains at stir zone (SZ) improved the strength of FFSSW joint. Energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis of specimen indicates the presence of Mg2Si precipitates in SZ. The fracture behavior of upper and lower interfaces was examined. The finer dimples are observed in fractograph, which confirm the ductile behaviour of fracture. The morphology at tool surfaces was also studied. The mechanical properties of three-sheet FFSSW joints were compared with other similar techniques of joining. Better understanding of mechanical properties and weld behavior of three sheets FFSSW is done with the help of fractography and SEM.