Dissimilar Aluminium Alloy Joints Research Articles

Enhancing weld joint performance of dissimilar aluminium alloy joints through filler rod selection

Enhancing weld joint performance of dissimilar aluminium alloy joints through filler rod selection

Effects of nano-modification on the microstrfuctural evolution and mechanical properties of AA7075/AA6061 aluminum alloy joints fabrica ted by laser-MIG hybrid welding technique

In this study, a rigorous comparative analysis is conducted to assess the implications of 7075 welding wire and 7075 welding wire fortified with 1.0 wt% of TiC nanoparticles on the microstructural characteristics, distribution patterns of secondary phases, grain refinement, and mechanical properties of AA7075/AA6061 dissimilar aluminum alloy joints produced via laser-MIG hybrid welding. The experimental results show that: The introduction of TiC nanoparticles prompts a transformation in the weld microstructure, transitioning from coarse dendritic morphologies to finer equiaxed dendritic structures. The grain size and the strengthening phases have both undergone a process of refinement. Notably, a marked increase in high-angle grain boundaries (HAGBs) and a concomitant decrease in low-angle grain boundaries (LAGBs) are observed in the nano-modified weld. Nano-modification yields substantial improvements in the mechanical properties of the welded joint. Specifically, the softening width of the AA6061 heat-affected zone (HAZ) is reduced by approximately half (from 8 mm to 4 mm), while the minimum microhardness of the joint has been increased from 34.1 Hv to 62.4 Hv. Moreover, the average ultimate tensile strength (UTS) of the joint has been enhanced from 95.7 MPa to 208.9 MPa, while the average yield strength (YS) has been increased from 57.1 MPa to 155.1 MPa.

Mechanical performance of dissimilar Al6082 aluminum and AZ91 magnesium alloy joints produced by friction stir welding

Abstract The current research work aims to produce a defect free joint of Al6082 aluminum and AZ91 magnesium alloy sheets by friction stir welding (FSW) at various tool rotational and travel speeds with an objective to obtain the best combination of welding parameters to produce quality joint. The weld joint that was produced at the combination of 1400 rpm tool rotational speed and 30 mm min−1 feed exhibited defect free stir zone. Microstructural studies carried out in the weld joint demonstrated mechanical mixing of base materials from both the alloys in the stir zone. The mixing of Al6082 and AZ91 alloys was clearly appeared in the weld zone. It can be observed that the x-ray diffraction studies clearly demonstrated the development of intermetallics in the weld region. Higher hardness was observed for the joints that can be ascertained to the presence of more mixed regions in the stir zone that contains hard and brittle intermetallics. From the tensile test data, lower strength (175.71 ± 4.24 MPa) was observed for the weld joint compared with Al6082 (242. 6 ± 11.4 MPa) and AZ91 (205.27 ± 6.39 MPa) base materials. Furthermore, the ductility of the weld joint was measured as marginally higher than the AZ91 Mg alloy and lower than the Al6082 alloy. It can be concluded that the defect free weld joints of Al6082-AZ91 alloys can be successfully produced by FSW for structural applications targeted for dry environment.

Research on the microstructure, mechanical and fatigue performance of 7075/6061 dissimilar aluminum alloy fusion welding joint treated by nanoparticle and post-weld heat treatment

The microstructure and mechanical properties of 7075/6061 high-strength dissimilar aluminum alloy fusion welds, after TiC nanoparticle-assisted welding and heat treatment, were discussed, and their fatigue performance was analyzed. The results indicate that the significant increase in hardness at the weld zone with T6 treatment compared to T5 is due to the solution treatment providing supersaturated solid solution for subsequent aging precipitation. T5 treatment causes the precipitation in the heat affected zones, thereby increasing the hardness of these regions. The joints exhibit excellent yield strength and tensile strength after heat treatment, with the elongation performance being optimal in T6 state. The fatigue performance of dissimilar aluminum alloy joints treated with nanoparticle and heat treatment is superior to the joints with single riveting. Porosity defects and microcracks generated during welding are prone to stress concentration, with interconnected pores and easily propagating cracks forming fatigue sources for pores and cracks. The crack propagation behavior is influenced by the pinning effect of TiC nanoparticles at the grain boundaries, and the second phase particles hinder crack propagation along the grain boundaries, forcing cracks to extend towards the 6061 side or the HAZ of the lower strength 6061 matrix. It demonstrates that the method of combining nanoparticle-assisted melt inert-gas welding and T6 heat treatment improves the fatigue life of 7075/6061 dissimilar aluminum alloy joints.

Effect of vibration frequency on mechanical properties and microstructure of metal inert gas welded dissimilar AA5083 and AA6061 aluminum alloy joints

This study explores how the frequency of vibrations affects the physical, mechanical, and residual stress properties in dissimilar metals welding between AA5083 and AA6061. The vibration-assisted welding process involves the application of vibration frequencies; 0 Hz, 10 Hz, 30 Hz, and 50 Hz. Weld joints were then examined for their microstructure, tensile strength and impact strength. They were also examined using X-ray diffraction to quantify surface residual stress. The findings suggest that welding with a 50 Hz vibration frequency produced weld metal characterized by a fine and consistent equiaxed microstructure. This welded joint exhibited exceptional mechanical property, boasting an ultimate tensile strength (UTS) of 197.87 MPa, an elongation of 15.28 %, and an impact strength of 8.10 J (J). Moreover, this welded joint displayed the lowest surface residual stress within the weld metal, measuring at 110.9 MPa. The application of high-frequency vibrations during aluminum welding promotes a more homogeneous mixing of molten metals between AA5083 and AA6061 in the weld metal. These vibrations also result in increased internal pressure within the molten weld metal, causing dissolved gas bubbles like H2, O2, and N2 to break and release.

High strain rate tensile deformation of similar and dissimilar AA6082 and AA7075 friction-stir-welded blanks

Friction-stir-welding process has become an established solid-state technique for joining of dissimilar lightweight materials over the past decade by overcoming fundamental welding challenges such as solidification cracking, phase segregation and surface oxidation. Despite these unique capabilities, the resulting microstructure feature in the weld zone consisting of fine grains with a high dislocation density, challenges further heat treatment and forming processes. Hence, a high solution annealing temperature results in degradation of the adjusted microstructure and in a lower to reduced mechanical properties in case of dissimilar joints of precipitation-hardenable aluminum alloys. Subsequent hot forming therefore involves a great effort and requires further heat treatment steps. Thus, the present study investigates the effect of a recently introduced novel thermo-mechanical forming process on local deformation behavior of similar as well as dissimilar joints processed by friction-stir-welding technique of thin-walled AA6082 and AA7075 blanks. To avoid the complete elimination of the adjusted microstructure, the welding process is performed after a thermo-mechanical process consisting of solution annealing, die cooling and peak aging. Uniaxial tensile tests are then carried out at high strain rates ranging from ε˙ = 40 s-1 to ε˙ = 400 s-1. The results show an increase in yield and ultimate tensile strength as well as in total elongation after failure with increasing strain rates. As the strain rate increases, the flow stress of similar weld of AA7075 is higher than those of AA6082 and the dissimilar weld of AA6082 and AA7075. Local deformation measurements reveal higher strain localization in the welded zone for similar welds, which leads to micro-crack initiation and failure due to strain accumulation. Microstructure analysis shows very fine equiaxed grain structure in the nugget zone and homogenous distribution of precipitates after friction stir welding process, which explain the plastic deformation behavior.

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.