Dissimilar Friction Stir Welding Research Articles

Microstructure and cryogenic mechanical properties of dissimilar friction stir welding joints between nitrogen-alloyed CoCrFeMnNi high-entropy alloy and high-manganese austenite steel

The microstructures and cryogenic mechanical properties of dissimilar friction stir welding (FSW) joints between nitrogen-alloyed CoCrFeMnNi high-entropy alloys (HEAs) and Fe–32.1Mn–7.5Cr–0.6Mo–1.2N steel were investigated. The results reveal that defect-free dissimilar joints can be achieved through FSW. Furthermore, the grains of nitrogen-alloyed CoCrFeMnNi HEAs in the stir zone of the dissimilar joint are significantly more refined than those of Fe–32.1Mn–7.5Cr–0.6Mo–1.2N steel. Joint efficiency at room and low temperature both exceed 90% of the base metal. Moreover, the cryogenic yield and ultimate strength of the dissimilar joints are higher than those recorded at room temperature. The fracture position is at the heat-affected zone of HEAs under two temperature conditions.

Simultaneous improvement in strength and ductility of friction stir welded Mg/Al joints by reducing micro-intermixing

Thread of pin has been proved beneficial to increasing shear action of tool and material intermixing, which however induces abundant formation of intermetallic compounds (IMCs) in Mg/Al dissimilar friction stir welding (FSW) leading to deteriorating the performance of joints. In this work, Mg alloy and Al alloy were well joined by threaded pin and unthreaded pin under the same welding parameters. For threaded pin joints, cracks occured in the banded structure (BS) region and bottom interface, then the main crack propagated along the Mg/Al interface, resulting in low strength and elongation. For unthreaded pin joints, necking and fracture occurred at the softened Al alloy to the retreating side (SAA-RS), and the fracture mode changed from brittle fracture (Mode I) to ductile fracture (Mode III). The tensile strength and strain of unthreaded pin joints are 201 MPa and 7.14 % respectively, significantly higher than those of threaded pin joints (i.e. 140 MPa and 1.15 %), and is the highest combination of strength and strain reported up until now. An unthreaded pin could reduce the local micro-intermixing between Mg and Al to suppress the formation of IMCs, which reduced the hardness in the BS region, preventing the formation and propagation of cracks.

Intermetallic Compounds Formation in Dissimilar Friction Stir Welding of Mg/Cu Alloys

Intermetallic Compounds Formation in Dissimilar Friction Stir Welding of Mg/Cu Alloys

A realization of Al/Ti dissimilar friction stir welding via bottom dynamic support using a Co-based alloy welding tool

A realization of Al/Ti dissimilar friction stir welding via bottom dynamic support using a Co-based alloy welding tool

Investigation on the mechanical properties and microstructural analysis of dissimilar friction stir welding of AA5154/AA7150

Butt welds were produced on AA5154/AA7150 using the FSW method, and measurements were taken for the hardness and elongation percentage of each joint. Regression analysis was utilized to investigate the significance of each parameter and formulate a mathematical relationship. Welding was performed at 1200 rpm, with a welding speed of 90 mm/min and a tool diameter of 28 mm, resulting in defect-free welds. Failures were commonly observed at the pin and the side of AA7150. To decrease the ultimate tensile strength (UTS), the welding speed (WS) or tool rotational speed (TRS) was increased. As both TRS and WS constitute the nugget zone, variations in hardness distribution were noted across the weld zones. ANOVA was applied in this study to establish the relative importance and influence of each factor on UTS. The ANOVA results indicated that all parameters significantly impacted UTS. Specifically, WS contributed 41.42%, diameter contributed 17.57%, and TRS contributed 13.27%. A quadratic model was also developed to describe the relationship between the factors and UTS values. Based on the data, a range of 0.41% to 10.36% differences existed between projected and actual values. The strength of the model was evaluated using R-Squared (R-Sq.), resulting in an obtained R-Sq. value of 0.892. This value indicates a robust relationship between the predicted and actual values.

Influence of Variation Ambient System on Dissimilar Friction Stir Welding of Al Alloy to Mg Alloy by the Addition of Nanoparticles and Interlayer

Influence of Variation Ambient System on Dissimilar Friction Stir Welding of Al Alloy to Mg Alloy by the Addition of Nanoparticles and Interlayer

A Physics-Informed Machine Learning Model of Dissimilar Friction Stir Welding to Tailor Residual Stress Using Coupled Eulerian and Lagrangian Approach

A Physics-Informed Machine Learning Model of Dissimilar Friction Stir Welding to Tailor Residual Stress Using Coupled Eulerian and Lagrangian Approach

Evaluation of Mechanical and Ballistic Properties of Dissimilar Aluminum Friction Stir Welded Joints

Evaluation of Mechanical and Ballistic Properties of Dissimilar Aluminum Friction Stir Welded Joints

Non-destructive detection and analysis of weld defects in dissimilar pulsed GMAW and FSW joints of aluminium castings and plates through 3D X-ray computed tomography

AbstractThis work focuses on porosity formation during the welding of dissimilar aluminium alloys (cast and sheet) by pulsed gas metal arc welding (GMAW) with different travel speeds (12–14 mm/s) and by friction stir welding (FSW). The case study concerns the assembling of a battery-pack enclosure prototype. The welded specimens were scanned by 3D X-ray computed tomography. The cast base material (BM) shows a porosity percentage of 1.45%, and it is characterized by pores with a strong hyperbolic relationship between equivalent diameter and sphericity. Considering the GMAW beads, porosity rises with the travel speed (from 1.80 to 5.12%), due to the reduction of the opening window in which pores can escape. Pores with volume higher than 0.10 mm3 rise with the travel speed, representing from 9.75 to 32.98% of the total porosity. These pores are responsible for the weaker hyperbolic connection for sphericity found for the GMAW beads. On the other hand, FSW mixes and homogenizes the pores in the cast BM. The novelty of the paper lays in proving the strong potentialities of FSW for weld porosity reduction. A re-designing of the battery-pack enclosures is necessary to limit arc welding in marginal areas, which are not crucial for sealing but necessary to create a stable platform to be subsequently sealed with FSW.

Effect of laser shock peening on stress corrosion cracking of TC4/2A14 dissimilar metal friction stir welding joints

Stress corrosion cracking (SCC) of welded joints is a significant issue that affects the widespread application of multimetal welded structures in aerospace, transportation, and other fields. This paper investigates the effect of laser shock peening (LSP) on the SCC of TC4/2A14 friction stir welded (FSW) joints with dissimilar metals. The microstructural evolution, mechanical properties, and corrosion behavior with and without LSP treatment were investigated using optical microscopy, transmission electron microscopy, X-ray analysis, electrochemical testing, and slow strain rate tensile testing (SSRT). The results showed that the LSP significantly refined the grains and induced work-hardening on the near-surface of the material. After LSP, the compressive residual stresses on the surface of the titanium and aluminium sides were −817.6 MPa and −153.6 MPa for the joint, respectively. Corrosion resistance was also improved, with the self-corrosion current density on the Al side of the joints reduced by 77% and the SCC susceptibility index (Issrt) reduced from 0.140 to 0.121. The enhanced SCC resistance of the LSP-treated TC4/2A14 dissimilar metal FSW joints is primarily due to grain refinement, work-hardening effect, and high-level compressive residual stress. These factors not only enhance the material strength and improve the pitting resistance of the joints but also prevent the initiation and propagation of SCC.

Investigation on Friction Stir Welding Parameters: Mechanical Properties, Correlations and Corrosion Behaviors of Aluminum/Titanium Dissimilar Welds

In industrial applications, welding of dissimilar metals such as aluminum (Al) and titanium (Ti) is a prerequisite for the development of hybrid components with improved mechanical and corrosion properties. However, dissimilar welding of the Al/Ti system is highly challenging due to differences in the physical and thermal properties of the two materials. In the present investigation, an attempt has been made to fabricate a dissimilar friction stir weld (FSW) of commercially pure Al and Ti and to elucidate the mechanism associated with superior joint formation. The process parameters, such as tool rotation speed, traverse speed and tool offset position have been optimized using Taguchi’s optimization technique. A detailed investigation of the weld with optimum process parameters has been carried out to reveal the mechanism of joint formation. The superior mechanical properties (24% higher ultimate tensile strength and 10% higher ductility than that of base Al) of the weld are attributed to the fabrication of a defect-free joint, formation of intercalated particles and an Al/Ti interlocking interface, homogeneous distribution of fine second-phase (Ti and/or intermetallics) particles in the weld nugget, reduction in the evolution of brittle Al3Ti intermetallic compounds (IMCs) and recrystallization and grain refinement of Al in the weld nugget. The potentio-dynamic polarization test indicated that the optimized Al/Ti weld has ~47% higher corrosion resistance than Al; it had a very mild corrosion attack due to the homogeneous dispersion of fine particles. The method and mechanism could have an immense influence on any dissimilar weld and metal matrix composites, improving their mechanical properties and corrosion resistance.

Material flow during dissimilar friction stir welding of Al/Mg alloys

Understanding of the intense in-process material flow during dissimilar friction stir welding (FSW) of Al/Mg alloys has long been limited by the accuracy of the numerical simulation model. In this paper, a computational fluid dynamics (CFD) simulation with state-of-the-art thermo-mechanical-flow fully coupled shear boundary model is employed to predict the material behavior during the dissimilar FSW of AA6061 Al alloy and AZ31B Mg alloy. The prediction on the three-dimensional temperature field and the flow field is obtained with the best accuracy to date. It is shown that the primary motion is rotation around the tool pin in the high-velocity zone (HVZ) near the welding tool, and there is a vertical component of velocity with a magnitude lower than 10 % of the total velocity. It is shown that the material is significantly redistributed during the welding process, with Mg alloy accumulating at the bottom and Al alloy accumulating at the upper part of the joint. The material distribution behavior is attributed to the material transfer in the through-thickness direction. In the HVZ, most material flows in the straight-through pattern and is slightly elevated when it flows through the tool vicinity. A small amount of Mg alloy flows in the maelstrom pattern, encircles the tool pin multiple times, and is transferred to a lower position. In this way, The upward transfer of Al alloy and the downward transfer of Mg alloy lead to the through-thickness redistribution of each alloy.

Dissimilar friction stir welding and post-weld heat treatment of Ti-6Al-4V and AA7075 producing joints of unprecedented strength

Dissimilar welding of Ti and Al alloys is challenging due to the potential formation of brittle intermetallics, which can compromise weld strength. Friction stir welding (FSW) is an advanced joining method with the potential to drastically reduce or prevent the formation of intermetallic phases because melting is avoided. However, in previous studies, dissimilar joints of Ti-6Al-4V and EN AW-7075 with satisfactory strength could not be achieved. Thus, we investigated friction stir welding of these two materials in a butt configuration, and analyzed the effects of post-weld heat treatments on the mechanical properties. Tensile strengths of 441 MPa in the as-welded condition and 505 MPa after heat treatment were achieved, significantly surpassing strength values reported in earlier studies. Microscopic investigations showed no evidence of formation of brittle intermetallic phases, and ductile fracture was observed. Our results show that FSW is a very promising candidate for future aerospace applications requiring dissimilar joining of Ti and Al alloys.

Effect of Tool Geometry on the Microstructure of Friction Stir Welding of Copper and 316L Stainless Steel

The microstructure evolution during dissimilar friction stir welding of copper with stainless steel 316L is studied. The welding is performed in transparence configuration using tools of two different geometries. The joints are characterized by optical microscopy, scanning and transmission electron microscopy, electron backscattered diffraction, and microhardness. The microstructure and crystallographic texture of base metals are significantly affected. The joint produced using a shoulder of 8 mm in diameter is characterized by a copper nugget with refined grains. The texture of copper is dominated by component of the shear texture. The steel beneath the tool shows a grain refinement with grains of sub‐micron size and a texture which is close to the ideal simple shear texture. For the joint produced by the 16 mm diameter tool shoulder, the nugget consists of large grains of copper, while the steel beneath the tool shows small recrystallized grains of micrometer size. The texture in the steel is dominated by the component of the shear texture. The Cu/316L interface in both types of joint is of very good quality. In a detailed study of the interface, it is revealed that the welding of metals is achieved by mutual intense mechanical interlocking without formation of any intermetallic compounds.

Microstructure, microhardness and mechanical behavior of dissimilar AA7075/AA6061 alloys under friction stir welding

Friction stir welding (FSW) of dissimilar AA6061 and AA7075 aluminum alloys faces challenges such as an unclear forming mechanism and low welding efficiency. In order to improve welding efficiency and elucidate the variations in metallography, Microhardness, and mechanical properties of dissimilar alloy FSW joints, this article designed FSW experiments using the Taguchi method with welding speeds ranging from 600 to 1000 mm/min. We studied the relationship between material mixing and welding defects through macroscopic metallography, microscopic metallography, and Microhardness, while the impact of welding parameters on the microstructure and properties was evaluated. The results show that void defects do not exist in dissimilar alloy FSW joints, and the Microhardness changes are “U” and “W” shaped. Material mixing played a decisive role in determining the microstructure and properties of dissimilar aluminum alloy FSW joints, with increased rotational speed enhancing material flow. The order of influence on the mechanical properties of the joint was found to be plunge depth, welding speed, and rotational speed. Under the conditions of 1000 mm/min, 2400 rpm, and 0.25 mm, the yield strength (YS) and ultimate tensile strength (UTS) of the dissimilar alloy FSW joints reached 87.3% and 73.4% of the AA6061-T6 alloy, respectively.

Mechanical properties and corrosion behaviour of dissimilar friction stir-welded Al 7075 and Mg AZ31 alloys with Cd and Zn interlayer

ABSTRACT The objective of present research work is to study joint strength and corrosion behaviour of dissimilar Friction Stir Welding (FSW) of Al 7075 and Mg AZ31 alloys with Cd and Zn interlayer. The FSW process performed at rotational speed 1300 rev min–1 and travel speed 20 mm min−1. The comparative study of mechanical properties and corrosion behaviour of FSW with Cd and Zn interlayers has been attempted for the first time. The result shows that the maximum tensile strength of 129 MPa has been achieved for FSW with Cd interlayer as compared to 85 MPa in the case of FSW with Zn interlayer. The corrosion rate was found in order of FSW with Cd > FSW with Zn > BM AZ31 > BM-7075. It has been concluded that FSW with Zn interlayer resulted in comparatively lower strength and better polarisation resistance than the FSW with Cd interlayer in 3.5 wt-% sodium chloride (NaCl) solution.

Effect of Residual Stress and Microstructure on the Fatigue Crack Growth Behavior of Aluminum Friction Stir Welded Joints.

Friction stir welding (FSW) has been adopted in the aerospace industry for fabricating structural alloys due to the low melting point and high thermal conductivity of aviation aluminum alloys. However, welding residual stresses can lead to secondary deformation in friction stir welded (FSWed) structures. Additionally, microstructural characteristics impact the crack growth rates and directions in these structures. Therefore, it is necessary to investigate the effects of residual stress and microstructure on the fatigue responses of FSWed joints. In this paper, we studied the fatigue crack growth behavior of two homogeneous and dissimilar FSWed joints with varying welding parameters, namely 2024-T3 and 7075-T6. The residual stresses were measured with the X-ray diffraction method. The dislocations and precipitates in different zones of the FSWed joints were analyzed via transmission electron microscopy (TEM). The results demonstrated that the residual stress significantly affected the fatigue crack growth rate and direction; the tensile residual stress promoted fatigue crack growth and offset the decrease in the fatigue crack growth rate that occurred due to grain refinement. The results of the microstructural analysis indicated that dislocation density and sliding resistance increased with the decrease in rotational speed and led to a decreased rate of fatigue crack propagation.

Optimization of mechanical and surface properties of friction stir welded dissimilar joint of 2507 SDSS and 317L ASS by controlling process parameters

Stainless steel welding has been widely used in industrial manufacturing, and friction stir welding has been recognized to reduce production costs significantly. To fully utilize the different properties of 2507 super duplex stainless steel (SDSS) and 317L austenitic stainless steel (ASS), the mechanical and surface properties of 2507 SDSS and 317L ASS dissimilar stainless steel joints were improved using the friction stir welding (FSW) method. The influence of rotation speed on the microstructural characteristics, mechanical properties, and corrosion behavior of the weld joints was investigated by welding at a constant speed of 20 mm/min within the range of 300–600 rpm. Specifically, at 400 rpm, a welded joint with optimal performance was obtained. When the rotation speed is 400 rpm, the yield strength (YS) and ultimate tensile strength (UTS) of the welding joint are 493 and 692 MPa, respectively, and the elongation (EL) is 32 %. The tensile strength is higher than 317L ASS but lower than 2507 SDSS, the EL is lower than those of 317L ASS and 2507 SDSS, and the friction coefficient of the welded joint is 0.93, which is between 317L ASS and 2507 SDSS. Notably, the refinement of grains in the stirred zone significantly improved the corrosion resistance of the welded joint, considerably exceeding that of the 317L ASS but still lower than the 2507 SDSS. This work can provide a process reference for studying the mechanical and corrosion properties of dissimilar stainless steel FSW.

Corrosion and microstructure evolution of ultrasonic (UaFSW), induction (i-FSW) and laser heating assisted macro and micro (μFSW) dissimilar friction stir welding and friction stir spot welding (FSSW) (surface and underwater deep sea) steels and Aluminum alloys.

Corrosion and microstructure evolution of ultrasonic (UaFSW), induction (i-FSW) and laser heating assisted macro and micro (μFSW) dissimilar friction stir welding and friction stir spot welding (FSSW) (surface and underwater deep sea) steels and Aluminum alloys.

Retracted: Effect of Tool Profile Influence in Dissimilar Friction Stir Welding of Aluminium Alloys (AA5083 and AA7068)

Retracted: Effect of Tool Profile Influence in Dissimilar Friction Stir Welding of Aluminium Alloys (AA5083 and AA7068)