Joining Of Dissimilar Materials Research Articles

Investigation of Laser Surface Texturing and Injection Molding Parameters in Advanced High‐Strength Steel‐Polyamide Direct Joining

This study investigates the joining of dissimilar materials, specifically galvannealed advanced high‐strength steel (AHSS) and glass fiber‐reinforced polyamide 6 (PA 6) to achieve lightweight automotive. AHSS and PA 6 are widely used in the automobile industry; however, a direct joining of those two materials is difficult owing to their great difference in physical properties. Therefore, laser surface texturing (LST) and plastic injection molding are adopted to join AHSS and PA 6, which can create a strong mechanical interlock between AHSS and PA 6, resulting in an excellent joint strength compared to other joining techniques. The effects of LST parameters (groove depth and hatch distance) and injection molding temperatures on the joint strength are examined. The maximum AHSS‐PA 6 joint strength is measured at 72.3 MPa. Additionally, the microstructure and mechanical properties of recast, which develops over the original metal surface by melting and resolidifying, are analyzed. Compared to the base metal, the recasts exhibit higher hardness due to smaller grain sizes. PA 6 fills the laser‐textured grooves and spaces between the recasts, acting as a mechanical interlock that enhances joint strength under tensile shear testing.

Pure copper coating by multibeam directed energy deposition with blue lasers for antimicrobial effect

Pure copper has antimicrobial effect, and the development of pure copper coating technology for product surfaces is needed to prevent the spread of infections. To achieve high antimicrobial performance in coatings, it is essential to form a coating with high copper purity and minimal defects. In this study, we attempted to form a pure copper coating layer on a SS304 substrate using multibeam directed energy deposition with blue diode lasers. In the coating layer formation process, multiple bead layers are overlapped to form a smooth surface and two different types of joining is conducted simultaneously: the similar material joining area with the remelted previous layer, and the dissimilar-material joining area with the substrate. However, it was challenging to conduct this process for SS304 and pure copper due to their significantly different thermal properties. Therefore, we varied the hatching distance to control the heat input to both joining areas and investigated the effect on the quality of the coating layer. The results showed that there is an optimal ratio of similar and dissimilar joining areas, at which a high-quality coating layer with few voids and low dilution is formed. Furthermore, antimicrobial tests showed that the pure copper coating layer formed in this study exhibited the antimicrobial performance equivalent to those of a pure copper plate.

Femtosecond laser joining of Stellite and stainless steel

This research explores the practicality of fusing Stellite 6, a cobalt-chromium alloy known for its high performance, with stainless steel, utilizing various laser welding approaches. The primary challenge addressed is the joining of dissimilar materials, which presents obstacles such as divergent melting points and disparate coefficients of thermal expansion. The aim is to achieve a metallurgical bond between Stellite and stainless steel that retains desirable properties. The study employs both continuous wave and femtosecond laser welding techniques, subjecting the resultant joints to rigorous analysis to assess their impact on the properties of the bond. Initial tensile testing delineated the intrinsic mechanical characteristics of the materials, revealing that while Stellite exhibits a lower ultimate tensile strength, it compensates with greater elongation compared to stainless steel. The use of continuous wave laser welding proved to be capable of creating the bond; however, it also precipitated a considerable decline in the tensile strength of the Stellite component as a result of the thermal processing involved. In contrast, femtosecond laser welding emerged as a more effective method, enhancing the joint’s overall strength and ductility. This improvement is attributed to the femtosecond laser’s precise control over thermal exposure, which confines the heat to the intended weld zone, thereby safeguarding the adjacent material from damage. Further insights were gleaned from Scanning Electron Microscopy, which showed a preferable intergranular fracture in samples welded with the femtosecond laser—a feature typically associated with ductile failure modes. The femtosecond laser welding approach culminated in a joint efficiency of 53.7%, mirroring the innate yield strength of the Stellite wire. This outcome suggests that such welded joints possess the requisite robustness for practical deployment, thus underscoring the potential of femtosecond laser welding in applications requiring the joining of Stellite to stainless steel.

Effects of temperature and stress evolution on microstructural change and mechanical properties during friction element welding

Dissimilar material joining is essential for improving the strength-to-weight ratio of materials for various applications. Friction element welding (FEW) is a promising solution for joining highly dissimilar materials that vary in strength and thickness. However, the influence of the process parameters on the material’s resultant microstructure and mechanical properties remains unclear. In this study, the relationship between microstructure and microhardness distribution of the welded specimen is experimentally studied, and the effects of temperature and stress evolution are revealed by a thermal–mechanical finite element model. It is found that the microhardness can be improved by over 50% in the central region due to microstructural change and grain refinement. The beneficial microstructural change can be achieved by inducing either a high peak temperature (over the austenitization temperature) or a high peak stress (over the hardening factor) during the FEW process, which can be obtained by controlling the endload and rotational speed of the friction element. The size of the region with improved hardness is observed to vary with the depth of deformation in the steel layer. For the transverse shear strength (TSS), it is observed that irrespective of the temperature levels reached, TSS increases with increasing stress in the steel layer. Temperature plays a crucial role when the steel layer’s temperature is higher than the austenitization start temperature wherein TSS increases with the temperature.

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.

Investigations on mechanical and surface properties of friction stir welded dissimilar joints of 2507 SDSS and 317L ASS

Friction stir welding (FSW), recognized as an eco-friendly and safe welding technique, finds widespread application across industries including aerospace, and automotive sectors. As a key material in production, stainless steel (SS) has great application potential in FSW. In this article, solid-state joining of dissimilar materials 2507 super duplex stainless steel (SDSS) and 317 L austenitic stainless steel (ASS), using FSW was investigated. By adjusting the position of 2507 SDSS and 317 L ASS, this paper examined the mechanical and surface properties of the joints at rotation speed of 400 rpm and welding speed of 20 mm/min. The results revealed that alteration of the material position seemed to have negligible influence on the joint's appearance, tensile behavior, and failure location. However, a clear grain refinement post-FSW in the joints was recorded, leading to a substantial increase in the hardness of the center stir zone (CSZ), alongside noticeably enhanced wear resistance. This grain refinement also contributed to an improvement in the corrosion resistance of the joints.

Study on Laser Transmission Welding Technology of TC4 Titanium Alloy and High-Borosilicate Glass.

As the demand for high-performance dissimilar material joining continues to increase in fields such as aerospace, biomedical engineering, and electronics, the welding technology of dissimilar materials has become a focus of research. However, due to the differences in material properties, particularly in the welding between metals and non-metals, numerous challenges arise. The formation and quality of the weld seam are strongly influenced by laser process parameters. In this study, successful welding of high-borosilicate glass to a TC4 titanium alloy, which was treated with high-temperature oxidation, was achieved using a millisecond pulsed laser. A series of process parameter comparison experiments were designed, and the laser welding behavior of the titanium alloy and glass under different process parameters was investigated using scanning electron microscopy (SEM) and a universal testing machine as the primary analysis and testing equipment. The results revealed that changes in process parameters significantly affect the energy input and accumulation during the welding process. The maximum joint strength of 60.67 N was obtained at a laser power of 180 W, a welding speed of 3 mm/s, a defocus distance of 0 mm, and a frequency of 10 Hz. Under the action of the laser, the two materials mixed and penetrated into the molten pool, thus achieving a connection. A phase, Ti5Si3, was detected at the fracture site, indicating that both mechanical bonding and chemical bonding reactions occurred between the high-borosilicate glass and the TC4 titanium alloy during the laser welding process.

Effect of variation in power input on dissimilar materials (Cu-Al) laser welding for battery manufacturing

Battery manufacturing inherently requires the joining of dissimilar materials. The performance of a joint is significantly derived from the joining technique as well as the process parameters, which, in turn, determine the life of the product. The current study discusses the efficacy of laser welding to develop dissimilar joints of thin sheets of Al and Cu for battery applications at varying power inputs. Thin sheets of aluminium and copper were welded using laser power inputs of 2.0 kW, 2.1 kW, and 2.2 kW. A power input of 2.1 kW results in 86 % higher weld penetration than the 2.0 kW. High power input results in through-thickness penetration, which drastically affects the mechanical strength of the joint. A weld joint developed at 2.1 kW shows a higher shear load of 800 N among all the power input parameters. An intermetallic layer forms at the weld interface for all three power inputs. However, the width of the intermetallic layer increases with the laser power input.

Diagnosis of Al-CFRTP TA-FSLW defect using acoustic emission signal based on SPWVD and ResNet

As one of the important development directions in modern railway and automobile, lightweight requires reliable connection technology of dissimilar materials. Thermal-assisted friction stir lap welding (TA-FSLW) is an available welding technology for the joining of dissimilar materials, which can solve the problems of physical and chemical properties in the welding process of dissimilar materials. Unfortunately, defects may occur during the welding process. This paper proposes a defect diagnosis method based on smooth pseudo Wigner-Ville distribution (SPWVD) and ResNet18 for Al-CFRTP TA-FSLW. Firstly, the acoustic emission (AE) signal and the temperature of the weld nugget are acquired by the AE sensor and thermography camera in the FSLW process. Then, the time–frequency domain features of AE signal are extracted by SPWVD, and the maximum temperature of the weld nugget is extracted by exponential moving average (EMA) from thermography. Moreover, the dataset is established by SPWVD features, maximum temperature of welding nugget, and several time–frequency features. Finally, the ResNet18-attention network is employed to classify welding defects and stages. The Al-CFRTP TA-FSLW experiments are carried out based on the proposed method. Experimental result indicates that the SPWVD spectrum can effectively extract the feature frequency of deep and shallow hole defects in the welding process. In the section of classification, the accuracy of the dataset with SPWVD features is improved by 2% to 4% compared to other methods, which demonstrates that the SPWVD feature is superior in defect feature extraction.

A State-of-the-Art Review on Direct Welding of Polymer to Metal for Structural Applications: Part 1 — Promising Processes

Structural lightweighting through the effective use of multiple materials has received increasing attention for fulfilling today’s demands for environmental sustainability in transportation systems. Direct dissimilar material joining methods (versus, e.g., traditional adhesive bonding or mechanical fastening) have become increasingly desirable since they offer process simplicity, production efficiency, and hermetic sealing, among others. In this two-part article, we provide a critical assessment of the state-of-the-art research and promising direct dissimilar material joining techniques reported over the last decades, with a particular emphasis on their potential for structural applications in Part I. As such, recent advances in advanced joint design and modeling methods for enabling optimum joint design for jointability and joint performance are presented along with some detailed examples for demonstrating their potential impacts on industrial applications in Part II. Finally, recommendations on future research and development directions are outlined for supporting the industry’s drive towards multi-material lightweighting.

Hybrid Joining of Dissimilar Thin Metallic Sheets—Mechanical Joining and Adhesive Bonding

This paper deals with joining dissimilar materials using thermal drilling technology as well as the combination of thermal drilling and adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, HSLA steel TL 1550-220 + Z, and structural aluminum alloy EN AW-6082 T6 (AlSi1MgMn). The geometry of the formed joints was tested metallographically as the load-bearing shear capacity under the tensile shear test of single-lapped joints and the resistance of the joints against corrosion-induced disbonding in a climate chamber. The energy dissipated by the joints up to fracture was calculated from the load–displacement curves. The hybrid joints were compared with the bonded joints with the same overlap area in terms of the load-bearing capacity and energy dissipated at joint failure. The hybrid joints formed by thermal drilling and adhesive bonding with a rubber-based adhesive confirmed the synergistic effect—the adhesive provides the high load-bearing capacity of the joint, and the bushing formed by thermal drilling increases the dissipated energy of the joint at failure. The exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints.

Bicontinuous microstructure formation of immiscible phases by the liquid metal replacement method and its application to Ti/Mg dissimilar joining

We designed a new microstructure control method (liquid metal replacement method) that creates entirely new composites using the original microstructure as a template. This method selectively replaces a specific phase from a composite with another phase based on differences in atomic interactions. We applied this method to the dissimilar material joining of immiscible titanium and magnesium. After diffusion bonding one side of an interlayer consisting of α-Ti / α-Sc phases to Ti, we butted the opposite side with Mg and reheated. At this interface, selective interdiffusion of Mg and Sc results in the replacement of only the α-Sc phase by the α-Mg phase, forming a new α-Ti / α-Mg bicontinuous microstructure using the α-Ti / α-Sc monotectoid microstructure as a template. The Sc that diffused to the Mg side formed a reaction layer where the MgSc (B2) and (Mg, Sc) solid solution coexisted. These novel composite structures and reaction layers strengthened the joint area. As a result, we suppressed fracture at the joint interface, causing fracture at Mg and achieving a maximum joint strength of 116 MPa.

Dissimilar material joining of densified superwood to aluminum by adhesive bonding

Superwood is a densified wood product that shows promise as a lightweight and renewable alternative for metallic materials. In order for this high-performance new material to be used in multi-material products, it must be able to be joined with other major materials. For example, joining superwood to aluminum would provide a key enabling technology for its use in automotive components since aluminum is presently a major lightweight material for such applications. In this paper, a methacrylate-based adhesive has been identified to provide high lap shear strength (7.5 MPa) for aluminum-to-superwood joints. The aluminum-to-superwood samples were prepared with different amounts of pre-polishing to create openings to the pores in the superwood so adhesive could penetrate into them and create a mechanical interlock, in addition to the hydrogen/chemical bonding at the surface between the methyl methacrylate (MMA) in methacrylate-based adhesive and the cellulose in superwood. For aluminum samples, a thin layer (typically a few nanometers) of oxide film on the surfaces provides hydrogen/chemical bond to MMA structure in the adhesive layer. The failure strength of the superwood-to-aluminum joint sample is about 50% higher than that of natural wood to natural wood joint sample and comparable to that of aluminum-to-aluminum joint sample.

A State-of-the-Art Review on Direct Welding of Polymer to Metal for Structural Applications: Part 2 — Joint Design and Property Characterization

Structural lightweighting through the effective use of multiple materials has received increasing attention for fulfilling today’s demands for environmental sustainability in transportation systems. Direct dissimilar material joining methods (versus, e.g., traditional adhesive bonding or mechanical fastening) have become increasingly desirable since they offer process simplicity, production efficiency, and hermetic sealing, among others. In Part I of this two-part article, we provided a critical assessment of the state-of-the-art research and promising direct dissimilar material joining techniques reported over the last decades, with a particular emphasis on their potential for structural applications. As such, in Part 2, recent advances in advanced joint design and modeling methods for enabling optimum joint design for joint ability and joint performance are presented along with some detailed examples for demonstrating their potential impacts on industrial applications. Finally, recommendations on future research and development directions are outlined for supporting the industry’s drive towards multi-material lightweighting.

Achieving Metallurgical Bonding in Aluminum/Steel Bimetallic Castings

Aluminum castings are increasingly being used in automotive powertrain and structural applications for vehicle lightweighting. Cast aluminum parts often need to be machined and joined to steel components in multi-material systems. Bimetallic components produced by casting aluminum over steel substrate are advantageous due to the elimination of machining and traditional dissimilar material joining processes. However, forming a strong metallurgical bonding during overcasting process has been challenging. In this paper, the effects of processing conditions such as substrate surface preparation, pre-heating temperature, melt conditions as well as casting design were studied by investigating the bimetallic interfaces for aluminum A319 casting alloy and a high alloy steel substrate in a sand-casting process. Zn and Al-based substrate coatings were evaluated. The experimental results suggest a metallurgical bond between aluminum and steel can be formed during the sand-casting process via high temperature diffusion with or without coatings. Al-based substrate coating prior to overcasting results in the formation of a continuous layer of intermetallics at the bimetallic interface, with large Al–Si–Fe intermetallics penetrating the cast aluminum.

Elucidation of dissimilar material joining phenomena on steel and aluminum alloy using hot-wire laser brazing

Elucidation of dissimilar material joining phenomena on steel and aluminum alloy using hot-wire laser brazing

A practical methodology for the fatigue life estimation of adhesive joints

The use of adhesives in structural joints as an alternative to traditional joining techniques, such as welding and rivets, is becoming increasingly popular in the transportation industry, including (but not limited to) automotive and aerospace. This trend is driven especially by the increasing need and focus on greener ways of transportation and the consequent light weighting requirements. Furthermore, adhesives have the significant advantage, over traditional joining techniques, of allowing joining of dissimilar materials, including composites. Therefore, to optimise the design of adhesively bonded structures and reduce the risk of in-service fatigue failures, the transportation industry needs efficient, robust, and easy-to-use approaches for the modelling and fatigue life estimation of adhesively bonded joints.This work presents a practical methodology for estimating the fatigue life of adhesively bonded joints that can be easily adopted by companies in the transportation industry. The proposed methodology includes Finite Element (FE) modelling guidelines to recover the required stresses along the bond lines, with limited changes to the typical FE modelling strategies currently used, especially in the automotive industry. It is proposed to model the adherends using shell elements and the adhesive layer with solid elements. The exposed edges of the adhesive are then wrapped with membrane shell elements used to extract the peel stresses. The solid elements and the shell elements are connected using ‘bonded contacts’ (or similar tools, depending on the FE software used). The proposed modelling guidelines provide FE models that are not computationally too onerous, with a good level of mesh insensitivity and that do not require congruent meshes. The peel stresses recovered from the FE model along the bond lines are then used as an input into nCode DesignLife to estimate the fatigue life of the bonded joints in the analysed structure. The fatigue life estimation is carried out using the standard nCode DesignLife SN analysis engine and bespoke SN curves obtained through testing of adhesively bonded specimens, representative of the joints in the production parts.

Corrosion Behavior of Al Alloy A6061 Jointed with High-Tensile Strength Steel By Friction Stir Welding in NaCl Solution

In recent years, weight reduction of automobile bodies has been effective in reducing carbon dioxide emissions. For this reason, the replacement of steel, which has a large specific gravity, with aluminum alloys and carbon fiber reinforced plastics is being promoted for the right materials in the right places. In this case, an appropriate dissimilar material joining method is needed in terms of ease of assembly, joining performance, and cost. Friction stir welding (FSW) has emerged as a promising joining method for a variety of engineering applications. FSW is a solid-phase joining technique that has been shown to have significant advantages over conventional welding in terms of the strength and quality of the joints produced. However, during joining of metallic materials by FSW, microstructural changes may occur that affect their corrosion degradation. In this study, the corrosion behavior of A6061 jointed with high-strength steel (SPCC980) by FSW in aqueous NaCl solution and the effect of Al alloy microstructural changes on it were investigated.In this study, FSW was performed on A6061 and SPCC980 steel plates, and galvanic corrosion behavior was investigated by immersion tests and surface observations, as well as electrochemical measurements of Al alloys. Immersion tests were performed in 1 M NaCl solution. Micro electrochemical polarization tests of A6061 were also performed to investigate the corrosion behavior.In the immersion test of the galvanic couple of A6061 and SPCC980 steel plates in NaCl solution, galvanic corrosion occurred with the Al alloy as the anode and the steel plate as the cathode, and hydrogen evolution was observed mainly from the BM site on A6061 in the initial stage of immersion. This is due to the hydrogen evolution reaction occurring inside the pitting corrosion of the A6061. The pits was formed near Fe-rich inclusions in the BM site. In the HAZ site, corrosion propagated from Fe-rich inclusions along grain boundaries, but no pitting corrosion was formed. In the NZ site, minor localized corrosion was developed. These results indicate that the susceptibility to localized corrosion and its morphology differ in each site on the A6061. The difference in localized corrosion susceptibility on the A6061 was considered to be caused by the difference in the distribution of Fe-rich inclusions. However, the fact that the size and number of Fe-rich inclusions in each site did not differ suggests that the difference in anodic dissolution activity near Fe-rich inclusions affects pitting corrosion susceptibility in each site. A6061 alloy is a precipitation-strengthened Al alloy reinforced by β'' phase, which is a metastable phase of Mg2Si, and dense precipitation of β'' phase was observed in the BM site. Therefore, the reason for the higher localized corrosion susceptibility of BM is related to the precipitation of the β'' phase.This paper is based on results obtained from a project, JPNP14014, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Development of a design space for dissimilar materials joining in aerospace applications

Abstract This research paper presents an application of the integrated process and product design (IPPD) approach for selecting the best joint configuration for dissimilar material joining in the early product design phase. The proposed methodology integrates the multi-criteria decision making (MCDM) approach with quality function deployment (QFD) to identify the key criteria for joint selection, including load-carrying capacity, size, cost per joint, ease of manufacturing, time consumption and deformation. Three types of joints (rivet, weld and adhesive) and two hybrid joints (adhesive-weld and adhesive-rivet) are considered for three dissimilar material configurations: carbon fiber-reinforced plastic (CFRP) aluminum, CFRP steel, and aluminum-steel. QFD is utilised to transform job requirements into design criteria, and in the second phase, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is employed to choose the optimal joint configuration based on the weighted criteria acquired in the previous phase. The selected joint configuration is then validated through experimental study. The findings demonstrate that the proposed IPPD approach with QFD-TOPSIS techniques is highly effective for selecting mechanical joints for dissimilar material joining in the early design phase. The study concludes that the adhesive-rivet hybrid joint is the optimal solution among all alternatives. The proposed methodology can ultimately lead to improved product reliability and performance, as well as reduced development time and cost.

Multilayer bonding of A1N30H foils to A1050 plates using cold spot forge welding

The cold spot forge-welding method, recently developed to achieve high-productivity and high-strength dissimilar material joining, was applied to multiple solid-phase joining of aluminum (Al) foils simulating tab-lead electrodes. Fifty Al foils of 12-μm thickness were sandwiched between 0.5 and 0.8 mm A1050 Al alloy plates and pressurized with 6-mm diameter punch for 1 s. The effect of bonding temperature (330–420 °C) and the reduction ratio (R, 1.4–3) on the tensile shear load of the joint was investigated. A lower R value at a higher bonding temperature resulted in base metal fracture (i.e., plug fracture) of the Al alloy plate. The maximum load reached 410 N using a reduction ratio of higher than 2.1 and bonding temperature of 420 °C. The processed foils were properly stretched in the plane without breakage, and a total of 51 sound layered bonded interfaces were formed. The results also confirmed that the oxide film became more rarefied with increasing R. These results are expected to be applicable to high-throughput, high-reliability bonding of secondary battery electrodes.