Dissimilar Material Joints Research Articles

Resistance spot welding of dissimilar material joints with a cold-gas-sprayed inlayer

In this publication, cold gas spraying (CGS) is investigated as an enabler for aluminum-steel joints. Using a powder-based coating process to adhere a steel layer to an aluminum substrate allows a steel component to be welded to the deposited layer by resistance spot welding. This method permits the metallurgical connection between similar materials to be separated, while mechanical bonding ensures the connection at the dissimilar aluminum-to-inlayer interface. A modification of the porous CGS layer, as well as the creation of the remelted zone in the aluminum, can be observed during the resistance spot welding process. Electron backscatter diffraction (EBSD) analyses show that the severely prestressed particles in the CGS coating recrystallize, which coincides with a decrease in defect density and hardness in the heat-affected zone. Microscopy of the aluminum substrate shows the creation of metallurgical pores as well as the expansion of pores attributed to the casting process. The rise in remelted aluminum hardness and decrease in the heat-affected zone of the CGS layer indicate the formation of a metallurgical notch.

Review of Recent Progress in Plasma-Facing Material Joints and Composites in the FRONTIER U.S.-Japan Collaboration

The plasma-facing components (PFCs) of future fusion reactors will have intricate structures and require multiple materials because no one material can simultaneously satisfy all the requirements of the component. The dissimilar material joints in PFCs must withstand extreme thermal and stress gradients under neutron irradiation. The Fusion Research Oriented to Neutron Irradiation and Tritium Behavior at Material Interfaces (FRONTIER) U.S.-Japan collaboration seeks to explore and explain the behavior of internal solid interfaces in PFCs under neutron irradiation. The first step of the collaboration was to identify the leading PFCs that should be studied further and prepare them for the next step, which will include neutron irradiation. Different strategies for material development are being pursued worldwide to produce robust PFCs. Here, an overview is presented of some of the most promising materials in the areas of copper alloys, tungsten-copper composites, tungsten-steel composites, additively manufactured tungsten, particle-reinforced tungsten, and tungsten and SiC fiber composites. Each material’s fabrication and benefits are described, and some discussion of remaining questions is given.

Effect of strength of steel sheets on peel tensile strength and failure mode of dissimilar joint of spot welds

Advanced high strength steel sheet (AHSS) is widely used in the automotive body for weight reduction and the improvement of crash performance. Peel tensile strength of spot welds tends to decrease as the steel sheet strength increases. Therefore, in order to further expand the application of AHSS, technology to prevent fracture of spot welds is required. In order to achieve that, it is necessary to understand the characteristics of spot-welded joints and clarify the controlling factors. However, most of the conventional joint strength evaluations have been conducted on the same kind material joints, and there are few systematic studies on the joint strength and fracture mode of dissimilar material joints that are often used in actual vehicles. Therefore, the purpose of this study is to obtain a guideline for grasping the characteristics of dissimilar joints in case of the plug failure. Using various joint shapes, we compared the peel tensile strength and failure position of the same kind material joints and the dissimilar material joints with the TS1500 MPa class hot-stamped steel sheet. As a result, it was found that the deformation behaviour of the test piece affects the joint strength and fracture position of the dissimilar material joints. Specifically, in dissimilar material joints, cross tension joints and double cup-shape tension joints tended to break on the TS1500 MPa class hot-stamped steel side. On the other hand, L-shape tension joints broke on the lower strength material side. From these results, it is considered important to understand their deformation behaviour in order to analyse and predict the fracture phenomenon of spot welds in actual vehicles and automotive parts.

Effect of strength of steel sheets on tensile shear strength and failure mode of dissimilar joint of spot welds

Advanced high strength steel sheet (AHSS) is widely used in the automotive body for weight reduction and the improvement of crash performance. For example, TS1500 MPa class hot stamped steel (1500HS steel) sheet is applied to many vehicle models. However, there is a concern that performance of spot welded joints will decline as steel strength increases. In order to further expand the application of AHSS, it is very important to have knowledge about the characteristics of spot welded joints. In this report, we investigated the tensile shear strength (TSS) of the 1500HS steel sheet. Then, we compared the joint strength and failure position of the same kind material joints and the dissimilar material joints with the 1500HS steel sheet in case of the plug failure. As a result, it was found that TSS of dissimilar material joints depend on base metal strength on lower strength steel side. However, fracture occurred on the 1500HS steel side except for joints with large difference of base metal strength. The mechanism is thought that the effect of strain concentration at the edge of nugget on the 1500HS steel side due to the increase of rotational deformation around the nugget.

Assessment of Adhesively Bonded Joints of Similar and Dissimilar Materials: Industrial Case Study

Joining similar or dissimilar materials has recently become a hot topic in industries. In this study, an adhesive technique was used to join plastic materials produced by additive manufacturing (3D printing) with metal materials. The effects of the type of material that forms the joint pairs on the joint strength were investigated. In addition, a case study was carried out on the “rubber-metal buffer” part, which is a rubber industry product. The “rubber-metal buffer” part, traditionally produced by vulcanization, was re-manufactured by changing the body material and production technique. Samples were produced from Tough PLA and TPU materials using a 3D printer at 80% and 100% fill rates. Adhesive joints were made by bonding dissimilar (Tough PLA/Galvanized steel, TPU/Galvanized steel, Tough PLA/TPU) and similar materials (Tough PLA/Tough PLA, TPU/TPU, Galvanized steel/Galvanized steel) using Loctite 9466 adhesive. The mechanical properties of the joints were determined using tensile and hardness tests, and then the damage mechanisms were examined. The highest strength value in similar material pairs (3D printed) was found in Tough PLA/Tough PLA joints (4 MPa). In dissimilar material pairs, the highest strength value was determined to be Tough PLA/Galvanized steel (4.17 MPa). As a result, it was found that TPU and Tough PLA materials produced by 3D printing can be used as an alternative to rubber.

Effect of induction preheating on microstructure and mechanical properties of friction stir welded dissimilar material joints of Inconel 718 and SS316L

Using an external heat source during friction stir welding (FSW) of high melting point materials is a promising approach to enhance the material flow and reduce the axial load, improving the tool life. In this study, conventional and induction heating-assisted friction stir welding (I-FSW) in joining dissimilar Inconel 718, and stainless steel (SS316L) alloy using the WC-10%Co tool was experimentally investigated. The welding was performed at a constant rotational speed of 300 rpm with welding speeds of 70 and 140 mm/min and 300 °C preheating temperature in the assisted FSW. The results show that the application of friction stir welding resulted in highly refined grains with deformed carbide particles in the stir zone of both materials, which increased mechanical properties. An increase in temperature during the I-FSW process led to a slight increase in the size of the particles and high atomic diffusion of Cr and Mo elements at the interface of the SS316L and Inconel 718 joint, which showed enhancement of the weld strength. In addition, highly dragged SS316L material into the advancing side of the Inconel 718 was observed, which was directly influenced by the preheating temperature and welding speed. The mechanical properties of the joint with preheating significantly improved at a high welding speed (i.e., at 140 mm/min). The tensile strength of the I-FSW joint at 140 mm/min was 683 MPa which was 99.8% of the base SS316L. Dynamic recrystallization resulted in grain refinement, which raised the hardness value. The results also show that preheating reduces downward axial force, enhancing the tool life.

Enhancement on the low-pressure shot peened process of monotonic plastic deformation behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel dissimilar joints using laser beam welding

This research paper mainly discusses the low-pressure shot-peened (LPSP) process of 2 mm thick sheet plates of monotonic mechanical behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel (SASS) dissimilar materials joint by laser beam welding. Three types of butt joint (Sample-1, Sample-2, and Sample-3) configuration methods of the laser beam welding process were implemented at the Ni–4Cu–3Mo alloy/SASS dissimilar weldments and LPSP weldments. The microstructure image of the fusion zone revealed that the high heat inputs were distributed at the grain boundary and the prior coarse grain structures were converted into NiCr and C–Cr with significant improvement in the α'-martensite structure. To achieve continuous improvement in yield strength of LPSP weldments compared to the dissimilar weldments, the plastic deformations rate was decreased in the shot-peened weldments. The base metals of tensile samples length were prepared as ±5 mm; however, samples clearly indicated that the dissimilar weldments and LPSP weldments showed the failure in the fusion zone. The average elongation of dissimilar LPSP weldments was increased by 13%; however, the heat inputs collapsed the grain boundaries growth and the structure was converted into twin boundaries and α-martensite structures. The hardness measurement at the fusion zone of dissimilar and LPSP weldments was performed and the average hardness value of 290 HV at the fusion zone and 211 HV at the heat-affected zone was observed for LPSP weldments. The fracture morphology revealed that neither major cracks nor minor voids at the fusion zone of the tensile sample were formed.

Transformation of the failure state for the clinched joints of dissimilar materials using an auxiliary layer

Clinched joints of dissimilar materials are prone to cracks in the neck during the forming process. A new method by introducing an auxiliary layer is used to eliminate defects in the neck of the clinched joint. In this paper, auxiliary layers were added to the HC340LA/AL5052 and AL6061/AL5052 joints to investigate their contribution to joint joinability. The geometric characteristics, mechanical features, failure mechanism, and fracture morphology of the joint were also analyzed. The results show that the auxiliary layer can reduce the stress concentration in the joint neck, thus eliminating the defects in the joint neck. And this effect is demonstrated in different clinching processes. Additionally, the joints with auxiliary layers have remarkable joint strength. Among them, HC340LA/AL5052 joints with an auxiliary layer can reach the highest strength of 6877 N. In comparison to the conventional round joint with auxiliary layer, the square joint with auxiliary layer exhibit higher joining strength.

Strength of dissimilar adhesively bonded DCB joints and its connection with the failure pressure of composite repair systems

The application of adhesively bonded joints in petroleum industry over other traditional joining methods has increased significantly in recent years mainly because of the potential for light weight structures, fast repairing systems and low temperature applications. The principal benefits are design flexibility and joining of dissimilar materials. Therefore, accurate analysis and study about the mechanical behavior of dissimilar materials joints are fundamentally required since composite materials are widely used as repair systems for metallic pipelines with localized flaws or damage that prejudice the serviceability. Experimental analyses were performed on dissimilar adhesively bonded DCB joints, similar to a composite repair applied to a pipeline, to investigate the design factors that affect the joint behavior. This study shows that the critical energy release rate obtained in dissimilar DCB joints tests can be correlated with the one obtained in hydrostatic tests performed in pipelines with though-wall defects repaired with composite sleeves. It is proposed an approximated theoretical framework that allows obtaining an estimate of critical fracture parameters that arise in composite repair standards only using simpler and less expensive DCB tests in the place o hydrostatic test.

Analysis of weld seam characteristic parameters identification for laser welding of dissimilar materials based on image segmentation

Welded joints of dissimilar materials increase the flexibility in design and manufacturing process greatly and, hence, have been widely used in aerospace, rail transportation, and other related industries. Due to the difference in physical and chemical properties of dissimilar materials, the formed weld during laser welding is different from that of the same material welding. The geometric morphology of the formed weld is an important factor affecting the welded joints performance. Therefore, an identification method of weld seam characteristic parameters is proposed in this paper for evaluating the welding quality by image segmentation in the laser welding of low carbon steel (Q235) and stainless steel (316L). The region of interest of the weld metallograph from experimental observation is defined, converted into grayscale image and then denoised by filter. The weld is segmented by the seeded region growing method with initial seed automatic selection. The weld seam characteristic parameters including the weld area, left weld width, right weld width, and weld penetration in the laser welding of dissimilar materials are identified based on the segmented image. The obtained results are validated by the experimental measurements of weld and good agreement between them has been found. The identified weld seam characteristic parameters are adopted for assessing weld fusion status, depth-to-width ratio, and symmetry quantitatively. The results indicate that the proposed method is reasonable and feasible for the weld quality evaluation to improve the laser welding quality of dissimilar materials in practical production.

Assessment of Composite Aluminum Adhesive Joints Using Digital Image Correlation

Traditional nondestructive evaluation (NDE) methods present significant challenges to detecting and characterizing kissing or weak bonds in adhesively bonded structures. These kissing or weak bonds also cannot transmit shear stresses or handle complex loading modes and, if not detected, can present a significant threat to the structural integrity of the components or systems. This paper demonstrates the digital image correlation (DIC) technique for evaluating adhesively bonded dissimilar materials joints subjected to kissing or weak bonds. The study employed four adhesively bonded carbon fiber reinforced plastics and aluminum (CFRP-Al) lap-shear test coupons with varied bond quality (i.e., with no contamination and three simulated kissing bond defects). The novelty of the approach presented in this paper was that this technique could detect and demonstrate changes in the normal strain (εyy) contour map of the contaminated specimens at relatively lower load levels. This load level corresponds to 15% of the failure load for the silicone and hydraulic oil contaminated sample and around 30% for the polyvinyl alcohol (PVA) contaminated sample. In addition, higher compressive strains along the overlap edges were observed in the strain map for the single lap joints due to the higher peeling stresses of the adherend and the stress concentration at the edges of an adhesively bonded joint.

Effect of Laser Shock Peening on High-Cycle Fatigue Performance of 1Cr18Ni9Ti/GH1140 Weld

The welded joints of 1Cr18Ni9Ti austenitic stainless steel and GH1140 nickel-based superalloy dissimilar materials used in certain types of aero-engine combustion liner components are prone to crack initiation during service, seriously affecting the service life of the combustion liner. In this study, laser shock peening (LSP) was applied to the dissimilar metal weld of 1Cr18Ni9Ti and GH1140, which are used in the combustion liner parts of aero engines. The effects of LSP on the residual stress, microhardness, microstructure and high-cycle fatigue performance of the weld were analyzed. The results show that the residual stress in the weld and heat-affected zones was converted from tensile residual stress to high amplitude compressive residual stress via LSP. Furthermore, the surface hardness of every region of the combustion liner weld was increased, especially in the weld zone, where an increase of 41.4% from 162 HV to 229 HV was observed. Simultaneously, with the introduction of grain refinement, gradient plastic deformation in the depth direction and the dislocation structure of the surface material, the high-cycle fatigue limit of the weld specimen was significantly increased and the fatigue limit of the 1Cr18Ni9Ti/GH1140 welded joint was improved by 65.39%, from 289 to 478 MPa.

Influence of cooling conditions on tensile lap shear strength and microstructure of friction stir welded aluminum alloy 5052-H32 and polycarbonate light weight hybrid joint

The joining of dissimilar materials, notably polymer and metal, is incredibly demanding due to the differences in the materials' mechanical, chemical, and thermal characteristics. In this present study, the feasibility analysis of dissimilar materials joints of aluminum alloy AA5052-H32 and polycarbonate (PC) was performed utilizing Friction Stir Welding (FSW) in the lap joint taper threaded tool pin profile. Response surface methodology (RSM) was implemented as a statistical design of the experiment tool for working process parameter optimization. Optical and Field emission scanning electron microscopy was employed to characterize the detailed microstructure of friction stir welded hybrid joint of AA5052-H32 alloy and PC. The mechanical and metallurgical findings demonstrate that AA5052-H32 and PC sheets were effectively bonded together utilizing a mix of macro mechanical interlocking and secondary chemical adhesive bonding of the materials, providing a viable relaxation to adhesive bonding or mechanical fastening. The hardness of the polymer in as-received conditions welded normally and in underwater conditions was measured onshore D hardness scale. The joint obtained at a rotational speed 1118 rpm and welding speed 48 mm/min with a 2° tilt angle had the maximum tensile lap shear strength of 14.86 MPa in air-cooled and 12.47 MPa in a water-cooled environment. Additionally, shore D hardness for optimal set of process parameters were 72 and 75 for air-cooled and water-cooled conditions respectively.

Assessment of the influence of FSSW parameters on shear strength of dissimilar materials joint (AA6061/AZ31B)

Due to their distinctive qualities, ultra-lightweight alloys like AA6061 and AZ31B find use in a variety of significant applications. However, they are challenging to fusion weld due to incompatible metallurgical properties that result in significant cooling stresses and solidification defects like hot cracking and porosity. To address the problems brought on by the fusion welding process, solid state technology is employed to combine various materials. The goal of this study is to pinpoint the impacts of friction stir spot welding process variables on shear fracture stress, including rotation speed, plunge rate, dwell period, and shoulder to pin diameter ratio. At a rotational speed of 1000 rpm, a plunge rate of 16 mm/min, a dwell time of 5 min, and a tool shoulder to pin diameter ratio of 2.5, the FSSW joint encounters a greater shear fracture strain. According to the hook height, width, and initiation point, an appropriate fracture load was discovered, which improved the mechanical and metallurgical qualities of the joints.

Physics-informed machine learning assisted uncertainty quantification for the corrosion of dissimilar material joints

Jointing techniques like the Self-Piercing Riveting (SPR), Resistance Spot Welding (RSW) and Rivet-Weld (RW) joints are used for mass production of dissimilar material joints due to their high performance, short cycle time, and adaptability. However, the service life and safety usage of these joints can be largely impacted by the galvanic corrosion due to the difference in equilibrium potentials between the metals with the presence of electrolyte. In this paper, we focus on Al-Fe galvanic corrosion and develop physics-informed machine learning based surrogate model for statistical corrosion analysis, which enables the reliability analysis of dissimilar material joints under corrosion environment. In this study, a physics-based finite element (FE) corrosion model has been developed to simulate the galvanic corrosion between a Fe cathode and an Al anode. Geometric and environmental factors including crevice gap, roughness of anode, conductivity, and the temperature of the electrolyte are investigated. Further, a thorough Uncertainty Quantification (UQ) analysis is conducted for the overall corrosion behavior of the Fe-Al joints. It is found that the electrolyte conductivity has the largest effects on the material loss and needs to be managed closely for better corrosion control. This will help in designing and manufacturing joints with improved corrosion performance.

Butted friction stir forming of AA6061-T6 to low carbon steel

Friction stir welding (FSW) is a popular method for creating dissimilar material joints in the aerospace and automotive industries. This work proposes a new FSW derivative process: butted friction stir forming (BFSF). BFSF has the distinction of joining two abutting workpieces to a lapped third workpiece. Additionally, the process does not require modification to traditional FSW equipment and tooling. In this study, BFSF combines two workpieces of aluminum alloy 6061-T6 in a butt weld configuration throughout the process. As the FSW tool traverses, it travels over preformed, threaded holes in low carbon ASTM A36 hot rolled steel at regular spacing. Downward force combined with the stirring action of the tool displaces material into the hole, filling the threads and forming a mechanical interlock. Testing of various screw sizes and thread pitches allowed the determination of the optimal joint configuration. Aluminum die-cut bolts of each size established a point of comparison for base material strength. Of the sizes tested, the ANSI metric M profile M9-1.25 screw had the highest mechanical strength. In cross-tensile testing, the average failure load was 3915 N. Shear testing produced a failure load of 5749 N. The M9-1.25 formed screws had a 33.6% decrease in strength compared to the die-cut bolts. While this strength reduction is higher than is often experienced in traditional FSW, the results of this study are a valid proof of concept for further development in BFSF methods.

Effects of lap configuration on mechanical properties and composition distribution of three-layer overlapped laser weldments on Al/Cu dissimilar materials

Battery cells are connected via bus-bars to meet performance requirements, such as power and capacity, and multiple layers of dissimilar materials functioning as anodes, cathodes, or bus-bars are overlapped and welded together. In laser welding, the formation of brittle intermetallic phases in the weld joint is inevitable and, in turn, deteriorates the mechanical properties. To obtain the desirable joint performance, appropriate welding parameters to avoid intermetallic phase formations and joint designs to release stress concentrations must be obtained. This study investigates the effects of lap configurations and process parameters on the tensile-shear load, T-peel load, and composition distribution when multi-layered joints of dissimilar materials are produced by laser welding. Two layers of 0.4 mm Al sheets were welded with a single 0.2 mm Cu sheet, which was emulated using electric vehicle battery interconnects. The results show that the penetration depth varied in accordance with the lap configuration even under the same heat input condition. The lap configuration and welding parameters influenced the composition distribution of the welds, as they altered the solidification rate, number of Cu/Al contact interfaces, and location of the high-density material. The failure load of the T-peel specimens was lower than that of the tensile-shear specimens except for the Cu − Al − Al lap configuration. The T-peel load of the Cu − Al − Al lap configuration was similar to that of the tensile-shear load. When the stress-concentrated joint was homogeneous, it was more robust.

Effect of Adhesive Layer Thickness and Slant Angle on Piezoelectric Bonded Joints

Piezoelectric materials have found their parts in numerous manufacturing applications such as transducers and sensors. Piezoelectric material shows anisotropy; in addition, its elastic field and electric field are integrated. The analysis of piezoelectric materials has obtained great interest among researchers with the development of smart structures. It is significant to explain the distribution of stress and electric displacement fields along the bonded edge. It has never been obvious how stress singularity and electric displacement fields are distributed at the vertex of piezoelectric dissimilar material joints. Stress and electric displacement distribution near the vertex along the interface of piezoelectric boned joints are investigated in this present research. Numerical analysis of piezoelectric dissimilar material joints is carried out by using Abaqus FEA software. From the numerical analysis, it is observed that stress, displacement, electric potential, electric displacement field evolvement along the interface edge rises with the increment of adhesive layer thickness and slant angle. So, a thin adhesive layer thickness and small slant angle are more reliable for operation.

Experimental evaluation of mode I fracture toughness of dissimilar-material joints with thermal residual stresses

The mode I interlaminar fracture toughness of dissimilar-material joints with thermal residual stresses is experimentally evaluated. The double cantilever beam (DCB) test is commonly used to assess the interlaminar fracture toughness of composites but is inadequate when dissimilar materials are joined owing to the mixed mode, which arises from differences in the bending stiffness and the thermal residual stresses formed during manufacturing because of differences in the linear expansion coefficient of the adherends. To address these difficulties, a new test, named the constant-load DCB test, was developed to evaluate the mode I interlaminar fracture toughness. In this study, a testing machine, based on the theoretical method previously established to derive the mode I interlaminar fracture toughness of dissimilar-material joints, is manufactured, and the fracture toughness is experimentally determined. As a result, good agreement between the theoretical value and experimental results is obtained, and the mode mixity ratio is significantly decreased compared with that of the general DCB test.

Microstructure and mechanical performance of dissimilar material joints of 2024Al and SiO2 glass by ultrasonic assisted soldering with Cu interlayer

Ultrasonic assisted soldering was used to join SiO2 glass and 2024Al with Sn solder. The soldering temperature and pressure were set at 300 °C and 0.2 MPa respectively. The Sn solder had good wettability on the SiO2 glass surface by ultrasonic cavitation. At the same time, ultrasonic accelerated the dissolution of 2024Al in molten Sn solder. With the extension of ultrasonic time, Sn solder had better wettability on the surface of base material. The shear strength of the SiO2/Sn/2024Al joint was stabilized at 14–17 MPa by ultrasonic wetting for 5 min before soldering. Due to the large residual stress in the joint, the brittle fracture of the glass occurred during the shear process. To improve the load capacity of the joint, Cu interlayer was added to the joint to relieve the thermal stress. Cu foil effectively relieved the residual stress of the joint during the cooling process. Molten Sn solder reacted with Cu foil and formed intermetallic compounds (IMCs). IMCs effectively block the deformation of filler metal and reduce the generation of stress. When the ultrasonic assisted soldering time was 5 s, the SiO2/Sn/Cu/Sn/2024Al joint reached the highest shear strength about 28 MPa.