Search Results (201)

This study develops an optimized femtosecond laser welding process for joining quartz glass and TC4 titanium alloy (Ti-6Al-4V) under non-optical contact conditions, specifically addressing the manufacturing needs of specialized photoelectric effect research containers. The joint primarily consists of parallel laser-welded zones (WZ) interspersed with base material. The defocus distance of the femtosecond laser predominantly influences the depth and phase composition of the WZ, while the weld spacing influences the crack distribution in the joint region. The maximum shear strength of 14.4 MPa was achieved at a defocusing distance of +0.1 mm (below the interface) and a weld spacing of 40 μm. The XRD stress measurements indicate that the defocusing distance mainly affects the stress along the direction of laser impact (DLI), whereas the weld spacing primarily influences the stress along the direction of spacing (DS). GPA results demonstrate that when the spacing is less than 30 μm, the non-uniform shrinkage inside the WZ induces tensile stress in the joint, leading to significant fluctuations in DS residual stress and consequently affecting the joint’s shear strength. This study investigates the effects of process parameters on the mechanical properties of dissimilar joints and, for the first time, analyzes the relationship between joint residual strain and femtosecond laser weld spacing, providing valuable insights for optimizing femtosecond laser welding processes. Full article

The friction surfacing (FS) process has emerged over the past few years as a method for joining both similar and dissimilar materials, for volume damage repair of defective components, and for corrosion protection. The possibility to produce a metallic coating by FS, without melting the material, classifies this technique as distinct from other standard methods. This unconventional deposition method is based on the severe plastic deformation that appears on a rotating metallic rod (consumable material) pressed against the substrate under an axial load. The present study aims to investigate the tribological properties and corrosion resistance provided by the aluminum-based FS coatings deposited onto a structural S235 steel substrate and further modified by plasma electrolytic oxidation (PEO). During the PEO treatment, the formation of a ceramic film is enabled, while the hardness, chemical stability, corrosion, and wear resistance of the modified surfaces are considerably increased. The morpho-structural characteristics and chemical composition of the PEO-modified FS coatings are further investigated using scanning electron microscopy combined with energy dispersive spectroscopy analysis and X-ray diffraction. Dry sliding wear testing of the PEO-modified aluminum-based coatings was carried out using a ball-on-disc configuration, while the corrosion resistance was electrochemically evaluated in a 3.5 wt.% NaCl solution. The corrosion rates of the aluminum-based coatings decreased significantly when the PEO treatment was applied, while the wear rate was substantially reduced compared to the untreated aluminum-based coating and steel substrate, respectively. Full article

Collision welding represents a promising solid-state joining technique for combining both similar and dissimilar metals without the thermal degradation of mechanical properties typically associated with fusion-based methods. This makes it particularly attractive for lightweight structural applications. In the context of collision welding, it is typically assumed that ideally smooth and defect-free surface conditions exist prior to welding. However, this does not consistently reflect industrial realities, where surface imperfections such as scratches are often unavoidable. Despite this, the influence of such surface irregularities on weld integrity and quality has not been comprehensively investigated to date. In this study, collision welding is applied to the material combination of AA6110A-T6 and AA6060-T6. Initially, the process window for this material combination is determined by systematically varying the collision velocity and collision angle—the two primary process parameters—using a special model test rig. Subsequently, the effect of surface imperfections in the form of defined scratch geometries on the resulting weld quality is investigated. In addition to evaluating the welding ratio and tensile shear strength, weld quality is assessed through scanning electron microscopy (SEM) of the bonding interface and high-speed imaging of jet formation during the collision process. Full article

Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships between microstructure, properties, and performance under load. FSSW offers numerous benefits over traditional welding, particularly for joining both similar and dissimilar materials. Key process parameters, including tool design, rotational speed, axial force, and dwell time, are discussed for their impact on weld quality. Innovations in robotics are enhancing FSSW’s accuracy and efficiency, while numerical simulations aid in optimizing process parameters and predicting material behavior. The addition of nano/microparticles, such as carbon nanotubes and graphene, has further improved weld strength and thermal stability. This review identifies areas for future research, including refining robotic programming, using artificial intelligence for autonomous welding, and exploring nano/microparticle reinforcement in FSSW composites. FSSW continues to advance solid-state joining technologies, providing critical insights for optimizing weld quality in sheet material applications. Full article

Adhesive bonding has emerged as a transformative joining method across multiple industries, offering lightweight, durable, and versatile alternatives to traditional fastening techniques. This review provides a comprehensive exploration of adhesive bonding, from fundamental adhesion mechanisms, mechanical and molecular, to application-specific criteria and the characteristics of common adhesive types. Emphasis is placed on challenges affecting bond quality and longevity, including defects such as kissing bonds, porosity, voids, poor cure, and substrate failures. Critical aspects of surface preparation, bond line thickness, and adhesive ageing under environmental stressors are analysed. Furthermore, this paper highlights the pressing need for sustainable solutions, including the disassembly and recyclability of bonded joints, particularly within the automotive and aerospace sectors. A key insight from this review is the lack of a unified framework to assess defect interaction, stochastic variability, and failure prediction, which is mainly due complexity of multi-defect interactions, the compositional expense of digital simulations, or the difficulty in obtaining sufficient statistical data needed for the stochastic models. This study underscores the necessity for multi-method detection approaches, advanced modelling techniques (i.e., debond-on-demand and bio-based formulations), and future research into defect correlation and sustainable adhesive technologies to improve reliability and support a circular materials economy. Full article

Magnetic pulse welding (MPW) is a promising solid-state joining process that utilizes electromagnetic forces to create high-speed, impact-like collisions between two metal components. This welding technique is widely known for its ability to join dissimilar metals, including aluminum, steel, and copper, without the need for additional filler materials or fluxes. MPW offers several advantages, such as minimal heat input, no distortion or warping, and excellent joint strength and integrity. The process is highly efficient, with welding times typically ranging from microseconds to milliseconds, making it suitable for high-volume production applications in sectors including automotive, aerospace, electronics, and various other industries where strong and reliable joints are required. It provides a cost-effective solution for joining lightweight materials, reducing weight and improving fuel efficiency in transportation systems. This contribution concerns an application for the automotive sector (body-in-white) and specifically examines the welding of AA6082-T6 aluminum alloy with HC420LA cold-rolled micro-alloyed steel. One of the main aspects for MPW optimization is the determination of the process window that does not depend on the equipment used but rather on the parameters associated with the physical mechanisms of the process. It was demonstrated that process windows based on contact angle versus output voltage diagrams can be of interest for production use for a given component (shock absorbers, suspension struts, chassis components, instrument panel beams, next-generation crash boxes, etc.). The process window based on impact pressures versus impact velocity for different impact angles, in addition to not depending on the equipment, allows highlighting other factors such as the pressure welding threshold for different temperatures in the impact zone, critical transition speeds for straight or wavy interface formation, and the jetting/no jetting effect transition. Experimental results demonstrated that optimal welding conditions are achieved with impact velocities between 900 and 1200 m/s, impact pressures of 3000–4000 MPa, and impact angles ranging from 18–35°. These conditions correspond to optimal technological parameters including gaps of 1.5–2 mm and output voltages between 7.5 and 8.5 kV. Successful welds require mean energy values above 20 kJ and weld specific energy values exceeding 150 kJ/m². The study establishes critical failure thresholds: welds consistently failed when gap distances exceeded 3 mm, output voltage dropped below 5.5 kV, or impact pressures fell below 2000 MPa. To determine these impact parameters, relationships based on Buckingham’s π theorem provide a viable solution closely aligned with experimental reality. Additionally, shear tests were conducted to determine weld cohesion, enabling the integration of mechanical resistance isovalues into the process window. The findings reveal an inverse relationship between impact angle and weld specific energy, with higher impact velocities producing thicker intermetallic compounds (IMCs), emphasizing the need for careful parameter optimization to balance weld strength and IMC formation. Full article

Friction Stir Welding (FSW) is a solid-state joining technique that has gained widespread adoption, particularly for aluminum alloys, due to its ability to produce high-quality welds without melting base materials. This comprehensive review focuses on the influence of process parameters on weld characteristics and performance. Compared to conventional fusion welding methods, FSW offers notable advantages, including superior mechanical properties, fewer defects, enhanced corrosion resistance, and lower environmental impact. The review also addresses key challenges such as tool wear, precise process control, and complications arising from welding dissimilar alloys. By synthesizing recent developments and case studies, this work outlines current limitations and proposes future directions for optimizing the FSW process to expand its applicability in critical engineering sectors. Full article

Ultrasonic welding has gained interest from various researchers and industries worldwide, particularly for joining dissimilar materials in sectors such as aerospace, aeronautics, and electronics. This paper presents a comprehensive bibliometric review aimed at mapping the evolving landscape of ultrasonic welding research. Through the systematic analysis of 1913 scientific documents, it identifies key advances, challenges, and future directions in the field. Furthermore, the bibliometric analysis sheds light on annual scientific production, prolific authors and institutions, scientific contribution per country, and methodological approaches. The global collaboration network comprises countries from all continents, with a prominent presence in Europe, Asia, and the Americas and less representation from African and Oceanian countries. China and the United States dominate the field in terms of scientific document production, international collaborations, and citations, with Germany also standing out for leading the number of citations in research related to hybrid metal/polymer joining. This review aims to serve as a valuable resource for researchers, practitioners, and policymakers interested in the advancements and future directions of ultrasonic welding for hybrid materials. Full article

The automotive and aerospace industries increasingly rely on lightweight, high-strength materials to improve fuel efficiency, making the joining of dissimilar metals such as aluminum and steel both beneficial and essential. However, a major challenge in these joints is the formation of brittle intermetallic compounds (IMCs) at the interface, even when using low heat-input solid-state welding methods like friction stir welding (FSW). Furthermore, IMC growth at elevated temperatures significantly limits the service life of these joints. In this study, an intermediate layer of stainless steel was deposited on the steel surface prior to FSW with aluminum. The resulting Al–Steel joints were subjected to heat treatment at 400 °C and 550 °C to investigate IMC growth and its impact on mechanical strength, with results compared to conventional joints without the intermediate layer. The intermediate layer significantly suppressed IMC formation, leading to a smaller reduction in mechanical strength after heat treatment. Joints with the intermediate layer achieved their highest strength (350 MPa) after heat treatment at 400 °C, while conventional joints exhibited their highest strength (225 MPa) in the as-welded condition. At 550 °C, both joint types experienced a decline in strength; however, the joint with the intermediate layer retained a strength of 100 MPa, whereas the conventional joint lost its strength entirely. This study provides an in-depth analysis of the role of IMC growth in joint strength and demonstrates how the intermediate layer enhances the thermal durability and mechanical performance of Al–Steel joints, offering valuable insights for their application in high-temperature environments. Full article

In the present research, laser circle welding (LCW) was proposed to join dual-phase steel (DP980) and carbon fiber-reinforced plastic (CFRP). The welding appearance, cross-section of the welded joint and fracture surfaces were subjected to multi-scale characterizations. Joining strength was evaluated by the single-lap shear test. Moreover, a numerical model was established based on the in-house finite element (FE) code JWRIAN-Hybrid to reproduce the thermal process of LCW. The results showed that successful bonding was achieved with a laser power higher than 300 W. The largest joining strength increased to about 1353.2 N (12.2 MPa) with 450 W laser power and then decreased under higher heat input. While the welded joint always presented brittle fracture, the joining zone could be divided into a squeezed zone (SZ), molten zone (MZ) and decomposition zone (DZ). The morphology of CFRP and chemical bonding information were distinct in each subregion. The chemical reaction between the O-C=O bond on the CFRP surface and the -OH bond on the DP980 sheet provided the joining force between dissimilar materials. Additionally, the developed FE model was effective in predicting the interfacial maximum temperature distribution of LCW. The influence of laser power on the joining strength of LCW joints was dualistic in character. The joining strength variation reflected the competitive result between joining zone expansion and local bonding quality change. Full article

This study presents a simple and innovative design to join a 2 mm thick steel sheet to a 5 mm thick aluminium sheet in a butt configuration. Thickness differences were addressed using support plates, while an aluminium run-on plate was employed to prevent the FSW tool from plunging into the steel. The process produced a unique S-shaped Al/St interface, the formation mechanism of which is analysed in this study. Scanning electron microscopy (SEM) observations revealed a gradient in the thickness of intermetallic compounds (IMCs) along the joint interface, decreasing from the top to the bottom. This S-shaped interface led to a 150% increase in the ultimate tensile strength (UTS) of the joint. The mechanism underlying this enhancement, attributed to the curved geometry of the interface and its alignment with the loading direction, is discussed in detail. These findings highlight the potential of this approach for improving the performance of dissimilar material joints in lightweight structural applications. Full article

Resistance Element Soldering (RES) is one of the new methods of joining dissimilar materials by resistance heating using an element. Sn60Pb40 solder, which has been used for decades in tin smithing and the electrical industry, has already been tested for joining galvanized steel sheet with thermoplastic using RES. However, legal restrictions are currently moving towards prohibiting the use of lead in mass production. For this reason, the possibility of replacing Sn60Pb40 solder with Sn91Zn9 lead-free solder was verified. The results showed that with an appropriate choice of flux and resistance heating conditions, it is possible to replace Sn60Pb40 solder with Sn91Zn9 solder when joining galvanized steel sheet with thermoplastic using RES. With a suitable heat input during soldering, good conditions were achieved for wetting the base material with molten solder with a sufficient volume of remelted solder in the core of the Cu/Sn91Zn9 bimetallic element. The strength of the soldered joint made at a heat input of 901 J was measured at the level of 94% of the strength of Sn91Zn9 solder. Full article

Ceramic matrix composites (CMCs) are composite materials made by using structural ceramics as matrix and reinforcing components such as high-strength fibers, whiskers, or particles. These materials are combined in a specific way to achieve a composite structure. With their excellent properties, including high specific strength, high specific stiffness, good thermal stability, oxidation resistance, and corrosion resistance, CMCs are widely used in the aerospace, automotive, energy, defense, and bio-medical fields. However, large and complex-shaped ceramic matrix composite parts are greatly influenced by factors such as the molding process, preparation costs, and consistency of quality, which makes the joining technology for CMCs increasingly important and a key trend for future development. However, due to the anisotropic nature of CMCs, the design of structural components varies, with different properties in different directions. Additionally, the chemical compatibility and physical matching between dissimilar materials in the joining process lead to much more complex joint design and strength analysis compared to traditional materials. This paper categorizes the joining technologies for CMCs into mechanical joining, bonding, soldering joining, and hybrid joining. Based on different joining techniques, the latest research progress on the joining of CMCs with themselves or with metals is reviewed. The advantages and disadvantages of each joining technology are summarized, and the future development trends of these joining technologies are analyzed. Predicting the performance of joining structures is currently a hot topic and challenge in research. Therefore, the study systematically reviews research combining failure mechanisms of ceramic matrix composite joining structures with finite element simulation techniques. Finally, the paper highlights the breakthroughs achieved in current research, as well as existing challenges, and outlines future research and application directions for ceramic matrix composite joining. Full article

In response to the growing demand for fuel economy and the imperative to reduce greenhouse gas emissions, the automotive industry has embraced structural lightweighting through multi-material solutions. This poses challenges in joining dissimilar lightweight metals, such as aluminum alloys to steels. The effects of the diameter of a weld nugget have been well documented, particularly in relation to its effects on the tensile strength, tensile fracture modes and fatigue behavior. For tensile shear specimens, various methods have been developed over the years to predict fracture modes by deriving the critical nugget diameter. However, these methods have proved inadequate for coach peel specimens, where a noteworthy observation is the occurrence of pull-out fracture modes with smaller weld nugget diameters than the critical diameter. In the present study, aluminum alloy sheets and steel sheets were resistance spot welded, achieving a deliberately reduced weld nugget diameter to induce an interfacial fracture mode in the tensile testing of coach peel specimens. Intriguingly, it was noted that fatigue fracture modes in the same coach peel specimens transitioned from pull-out to interfacial with decreasing applied loads, challenging conventional expectations. Furthermore, finite element analysis was performed, and the findings indicated that the fracture modes of the coach peel specimens were influenced not only by the diameter of the weld nugget but also by local stress states, specifically the stress triaxiality at the tips of the spot weld notches. Full article

Currently, the quartz glass–TC4 dissimilar joint has been applied in fields such as radiation environment testing, reactor engineering, and other areas. However, the high brittleness of the quartz glass and thermal mismatch during the welding process limit require further development. Thus, a femtosecond laser was employed to perform the direct joining of these materials under non-optical contact conditions, with the aid of a well-designed clamp and optimized process, and the effect of pulse energy on the microstructure and mechanical properties was analyzed. It was revealed that a lot of welding zones form at the interface through the diffusion of Si, O, and Ti and, thus, consist of a stable joint. Element distribution is related to pulse energy, which can affect the composition of secondary phases in the weld zones. The maximum shear strength of joints was 10.4 MPa with laser pulses of 0.3 mJ, while a further increase in the pulse energy led to more defects and stress unevenness. These findings provide valuable insights into enhancing the reliability of metal–glass welding joints and the promotion of femtosecond laser technology. Full article