Dissimilar Aluminum Alloys Research Articles

Parameter Optimization for Dissimilar Aluminum Alloys Joined Using Friction Stir Additive Manufacturing: A Screening Study

ABSTRACTDue to the requirement for better strength‐to‐weight ratios, the utilisation of aluminum alloys is rapidly expanding. Lightweight components are of utmost importance in most industries, particularly in transportation, aviation, maritime, automotive, and other industries. These lightweight engineering materials are hard to be joined utilising traditional fusion joining techniques, necessitating the development of alternative joining techniques. The novel friction‐stir additive manufacturing (FSAM) technique, based on the concept of friction stir welding (FSW), can be used to combine aluminum alloys additively in their solid state. This work examines the effects of several process parameters (tool rotational speed, tool tilt angle, and tool transverse speed) on tensile strength and hardness using a 3‐factor L9 Taguchi designed experiment. Three cases were explored, one were AL 6061 was welded to AL 7075, one where AL 7075 was welded to AL 6061, and one where the data were mixed to get an “average” effect representative of large additively manufactured parts. A detailed ANOVA (including both main effects and interactions analyses) provided clear guidance on the optimization of the parameters for several objectives. This work will contribute to the development and wider use of FSAM in both industrial and academic research settings by providing a useful dataset and clear parameter selection guidance. The results of this research indicate that the FSAM methodology could be utilized to fabricate large defect‐free structures, which can be a suitable replacement for the traditional Al6061 material used in automotive and aerospace sectors.

Enhancing performance through friction welding of dissimilar aluminium 2014 and 7075 hybrid metal-matrix composite: insights into material characterization, crystallographic texture, and mechanical properties

Abstract Welding high-strength, age-hardenable aluminium alloys from the 2XXX and 7XXX series poses challenges when using fusion-based welding processes. Common issues such as hydrogen porosity, hot cracking, stress corrosion cracking, and solidification cracking can lead to a reduction in mechanical properties due to the loss of strengthening precipitates and alloying elements. Consequently, friction stir welding (FSW) has emerged as a promising solid-state welding technique for joining dissimilar aluminium alloys and composites, particularly in aerospace applications where a combination of strength, corrosion resistance, and other desirable properties is required. This study investigates the FSW of dissimilar aluminium alloys, specifically AA2014 and a hybrid metal-matrix composite of AA7075 reinforced with silicon carbide and graphite particles. The microstructural and mechanical properties of the welded joints were characterized, revealing an average grain size of 2.39 μm ± 1.2 in the stir zone (SZ). A high angle grain boundary volume fraction of 47.25% was observed in the SZ, compared to 2.01% in the AA7075 composite and 15.03% in the AA2014 base metal. The presence of shear textures and the distribution of cube, S, and H textures indicate a homogeneous mixing of the base materials and a high shear strain rate during welding. The hardness of the SZ increased by 13%, and the ultimate tensile strength, yield strength, and elongation of the joint were measured at 251 MPa, 183 MPa, and 6.44%, respectively. The flexural strength of the joints improved significantly, with the CW13 sample showing a 67% increase compared to CW1. The dissimilar joint CW13, welded at 12.5 mm min−1, achieved a maximum joint efficiency of 95%.

Optimal Tungsten Inert Gas Welding Parameters of Dissimilar Aluminum Alloys Al 7075 and Al 6061 Using Ultrasonic Vibration and Nanocomposite Filler (Al 5356/ZrB2) to Alleviate Hot Cracking Phenomenon

Abstract In this study, the welding of dissimilar aluminum alloys, Al 7075 and Al 6061, was investigated using Al 5356 filler rods reinforced with ZrB2 particles. The welding process was conducted using tungsten inert gas (TIG) welding, with and without ultrasonic vibration, to enhance weld quality and reduce hot cracking. Optimization of process parameters for dissimilar TIG welding was performed through Response Surface Methodology (RSM), which generated a design matrix to analyze the influence of process parameters on response variables. Numerical and graphical optimization was applied to minimize hot cracking sensitivity and maximize microhardness. The RSM-based models suggested an optimal welding current of 93 A, the use of Al 5356/ZrB2 nanocomposite filler, and the application of ultrasonic vibrations. Experimental validation of the identified solution demonstrated improvements in weld quality, including increased yield strength and ductility. The combination of nano-reinforced fillers and ultrasonic vibrations was found to enhance weldability and mitigate hot cracking in dissimilar aluminum joints. The mechanism of hot cracking reduction involved grain refinement, degassing, and homogenization due to ultrasonic vibrations, as well as the modification of weld pool chemistry and control of dilution by the nanocomposite filler, which collectively minimized solidification shrinkage and stress. Under these optimized conditions, no hot cracking was observed experimentally.

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.

A study on friction stir welding with dissimilar aluminium alloys using various tool profiles

A study on friction stir welding with dissimilar aluminium alloys using various tool profiles

Characteristics of Dissimilar AA5083 and AA7050 Aluminium Alloys Friction Stir Butt Welded with Different Tool Axis Offsets

Characteristics of Dissimilar AA5083 and AA7050 Aluminium Alloys Friction Stir Butt Welded with Different Tool Axis Offsets

Interface microstructure and healing mechanism of Al/Al composites by hot compression bonding

To understand the interfacial evolution of heterogeneous aluminum alloys in detail, this study investigated bilayers and extended to investigate multilayer heterogeneous aluminum (MHA)11multilayer heterogeneous aluminum (MHA) alloys. Hot compression bonding (HCB)22Hot compression bonding (HCB) was used to investigate the interface healing mechanism of 7075Al/Pure Al at 450℃ in different processing conditions. Subsequent post-holding treatment of different durations were carried out to investigate the microstructure, the evolution of intermetallic compounds (IMCs)33intermetallic compounds (IMCs) and interfacial oxides of the bonded interface. The results show that during the bonding of dissimilar aluminum alloys, IMCs and substantial oxides formed at the layer interfaces under high temperatures and strain rates. Post-holding treatment facilitates the decomposition and transformation of these oxides, thereby enhancing interface healing. The optimal interfacial bonding between the two aluminum alloys is attained at a strain rate of 0.001 s−1 followed by a post-holding treatment for 60 min, MHA at various strains is produced using the same procedure. The prepared MHA features a continuous and flat interface, but there are still discontinuous micropores and voids. As deformation increases, the degree of recrystallization on the 7075Al side also increases. Defects progressively vanish as grain boundary migration replaces the original bonding interfaces, thereby enhancing interface bonding quality. These studies may provide guidance for the preparation of heterogeneous layered composites.

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.

Effects of ultrasonic vibration on residual stress distribution and local mechanical properties of AA6061/Ti6Al4V dissimilar joints by resistance spot welding

The joining of dissimilar titanium and aluminum alloys has potential applications in railway and aerospace industries, owing to substantial weight reduction and better economic viability. In this study, the residual stress distribution and local mechanical performance of ultrasonic-assisted resistance spot welding (UaRSW) welds were investigated. The welding current, welding time, and electrode force of the RSW process were set as 9.0 kA, 350 ms, and 1.0 kN respectively, and the frequency and power of ultrasonic vibration were 20 kHz and 800 W. The residual stress was evaluated by X-ray diffraction (XRD) method and numerical simulation, and these methods showed a reasonable match. There was tensile residual stress distributed on RSW welds and UaRSW welds, but the value of residual stress was reduced by about 30% at welding nugget and 20% at heat affected zone (HAZ) with the ultrasonic vibration, the reduction of residual stress in UaRSW welds was attributed to the more uniform temperature distribution and lower plastic deformation resistant of AA6061. The welding peak temperature was decreased from 1673.4 °C to 1584.2 °C with the ultrasonic vibration, resulted from the modified Al/Ti contact surface and reduced contact resistance. The miniature tensile test results showed the improvement of mechanical performance by ultrasonic vibration. The maximum load of welding nugget region increased from 19.6 N to 22.3 N, and the elongation obtained 10% increase. This hybrid welding technique shows a potential to improve the quality of welds with ensured efficiency, which is also simple to realize automation in the manufacturing industry.

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.

Improvement of Mechanical Properties and Corrosion Resistance of Friction Stir Welded Joints Made of Dissimilar Aluminum Alloys Through Scandium-Enriched Alloy Powder Incorporation

Improvement of Mechanical Properties and Corrosion Resistance of Friction Stir Welded Joints Made of Dissimilar Aluminum Alloys Through Scandium-Enriched Alloy Powder Incorporation

Investigating the influence of stress ratio variation on the crack growth rate in friction stir welded dissimilar aluminum alloys

This research focuses on the friction stir welding (FSW) of dissimilar aluminum alloys AA2024 and AA7075 and investigates the effect of different stress ratios on crack growth within dissimilar welded joints. The FSW process was performed at 760 rpm rotational speed and a feed rate of 50 mm/min. Subsequent crack growth tests were conducted on Compact Tension (CT) specimens extracted from the dissimilar FSW joint, applying varying stress ratios (R: −0.5, 0.0, 0.1, 0.5, 0.8) at a maximum load (Pmax) of 5 kN and a frequency of 6 Hz.The study meticulously analyzed and compared the tensile properties of weld joints and base metals. The hardness profile was plotted across the various weld zones. Experimental data were utilized to construct fundamental curves such as the a-N curve, crack growth rate curve, and stress–strain curve, enabling the determination of Paris constants. Notably, the research unveiled a clear relationship between stress ratio and fatigue life, indicating a decrease in fatigue life as the stress ratio increased. Specifically, the highest fatigue life of 45,000 cycles was observed at R=−0.5, while the lowest of 26,000 cycles was noted at R=0.8. Furthermore, electron microscopy was employed to scrutinize the fracture surface, providing valuable insights into its behavior.

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%.

Progressive Effect of Dual-Hybridization in Friction Stir Welding by Ultrasonic Energy and Electric Current for Joining Dissimilar Material Al6063 Aluminum Alloy and C26000 Copper Alloy

Progressive Effect of Dual-Hybridization in Friction Stir Welding by Ultrasonic Energy and Electric Current for Joining Dissimilar Material Al6063 Aluminum Alloy and C26000 Copper Alloy

Integrating Numerical Simulation and Experimental Validation to Analyze Temperature Distribution in Friction Stir Welding of Dissimilar Aluminum Alloy

This study explores the temperature distribution in Aluminum alloys, specifically AA2024 T351 and AA6351 T6, during friction stir welding (FSW). Utilizing COMSOL Multiphysics software, the research investigates FSW at rotational speeds of 800, 1200, and 1600 rpm, while maintaining a constant welding speed (35 mm/min) and axial force (3 kN). The simulation incorporates temperature-dependent material properties. The findings reveal that the maximum temperature occurs at the upper part of the stir zone for both alloys. Experimental validation demonstrates excellent agreement with the simulated temperature distribution, reaffirming the accuracy of the COMSOL Multiphysics model.

Grain Structure and Texture Evolution in the Bottom Zone of Dissimilar Friction-Stir-Welded AA2024-T351 and AA7075-T651 Joints.

High-strength dissimilar aluminum alloys are difficult to connect by fusion welding, while they can be successfully joined by friction stir welding (FSW). However, the asymmetrical deformation and heat input that occur during FSW result in the formation of a heterogeneous microstructure in their welded zone. In this work, the grain structure and texture evolution in the bottom zones of dissimilar FSW AA2024-T351 and AA7075-T651 joints at different welding speeds (feeding speeds) were quantitatively investigated. The results indicated that dynamic recrystallization occurs in the bottom zones of dissimilar FSW joints, and equiaxed grains with low grain sizes are formed at the welding speed of 60-240 mm/min. A high fraction of the recrystallized grains were generated in the bottom zones of the joints at a low welding speed, while a high fraction of the substructured grains are produced at a high welding speed. Different types of shear textures are produced in the bottom zones of the joints; the number fraction of shear texture types depends on different welding speeds. This study helps to understand the mechanism of microstructure homogenization in dissimilar FSW joints and provides a basis for further improving the microstructure of the welded zone for engineering applications.

Influence of material position and tool axis offset on the stir zone material flow and joint integrity of friction stir welded dissimilar AA5083 and AA7050 alloys

The present investigation aims to establish the influence of tool axis offset and the relative position of materials on the stir zone (SZ) material flow and joint characteristics of friction stir (FS) butt welded dissimilar AA5083-H111 and AA7050-T7651 aluminium alloys. The FS welding trials were conducted by systematically varying the tool axis offset from zero to 1 mm, with an increment of 0.25 mm, to both the advancing side (AS) and retreating side (RS) of the joint by keeping AA7050 and AA5083 alloys at the AS and RS of the joint, respectively. The welding speed, tool rotational speed, axial force and tool tilt angle were held constant. The results showed that for the given relative position of the alloys, the tool axis offset has significant influence on the SZ material flow pattern and the evolution of microstructure in the joint zone. The microhardness has a heterogeneous distribution across the joint and it is found to be sensitive to the tool axis offset. The highest hardness values are observed for the joints FS welded at 1 mm tool axis offset to the AS and the lowest for the joints welded at 1 mm tool axis offset to the RS of the joint. The joint fabricated at 0.5 mm tool axis offset to the AS has exhibited the highest joint strength of 303 MPa (joint efficiency of 98.4 %). Also, within the limits of tool axis offset experimented, the joint integrity is less sensitive to the variation of tool axis offset to both the AS and RS of the joint. The softening of the HAZ on the weaker AA5083 alloy side (for high heat generation cases) and the weakening of the SZ towards the bottom (for low heat generation cases) are the main factors limiting the joint strength. The studies showed that in FSW of dissimilar 5xxx and 7xxx alloys, appropriate selection of tool axis offset and relative position of the alloys are critical for producing joints with excellent joint efficiency.

Influence of welding parameters and post weld heat treatment on mechanical, microstructures and corrosion behaviour of friction stir welded aluminium alloys

A study on how corrosion and mechanical characteristics of friction stir welded joints are affected by processing parameters employed during the welding and the post-weld heat treatment administered on the welded materials has been reported in this paper. This study specifically investigated the effects of variable parameters such as the tool rotational and welding speeds and the post-weld heat treatment on the mechanical and corrosion behaviour of the friction stir welded dissimilar 6101-T6 and 7075-T651 Aluminium Alloys. The welded samples were characterized by the evolving microstructure and mechanical characteristics. The results show that the tensile strength of the joints decreases from 154 MPa to 144 MPa when the rotational speed increases from 950 rpm to 1550 rpm. However, the tensile strength increases from 138 MPa to 154 MPa with an increase in the welding speed from 20 mm/min to 110 mm/min. This is due to high heat input at higher rotational speed which weakens the bonding strength at the joints. The corrosion behaviour was observed to differ at different parameters. The corrosion inhibition efficiency was highest at a rotational speed of 950 rpm, welding speed of 65 mm/min, and lowest at 950 rpm and 20 mm/min. It was observed that the Post-Weld Heat Treatment (PWHT) process enhanced the mechanical properties as a result of an improvement in the grain refinement but lowered the corrosion resistance. This study is significant as it informs the basis for the optimization of processing parameters and post weld heat treatment for dissimilar aluminium alloys for the grades considered in this study.

Characteristics analysis and monitoring of friction stir welded dissimilar AA5083/AA6061-T6 using acoustic emission technique

The joining of aluminum alloys using fusion welding often leads to issues such as hot tears, porosity, distortion, and solidifying cracks. To address these challenges, solid-state welding processes like Friction Stir Welding (FSW) are preferable. This study investigates the FSW of dissimilar aluminum alloys AA 5083 and AA 6061-T6, employing Acoustic Emission (AE) techniques for real-time monitoring. FSW was conducted under conditions with no defects, pinhole defects, and piping defects. The resulting joints were evaluated for their mechanical properties and metallurgical characteristics. Microstructural analysis was performed using an optical microscope, revealing that the defect-free condition achieved the highest tensile strength of 256 MPa and superior hardness of 93 HV at the stir zone. Tensile failure commonly manifested within the heat-affected zone (HAZ) of AA 6061-T6, primarily due to grain enlargement and the impact of Mg2Si precipitates. Examination of the fractured regions via scanning electron microscopy revealed ductile-mode fractures featuring elongated dimples and microvoids. AE parameters such as hits, amplitude RMS, and energy were analyzed, demonstrating that defect-free welds had consistent AE signal patterns, while significant variations were observed in pinhole and piping defect conditions due to larger defect areas. The findings suggest that AE monitoring is effective in detecting and analyzing welding defects, providing valuable insights into the FSW process for dissimilar aluminum alloys.