Search Results (556)

Aluminum matrix composites provide an ideal solution for lightweight brake disks, but conventional casting processes are prone to crack initiation due to inhomogeneous reinforcement dispersion, gas porosity, and inadequate toughness. To break the conventional trade-off between high wear resistance and low toughness of brake disks, this study fabricated a bimetallic structure of SiC_p/Al–Fe–V–Si aluminum matrix composite and cast ZL101 alloy using friction stir lap welding (FSLW). Then, the microstructural evolution, mechanical properties, and tribological behavior of the FSLW joints were studied by XRD, SEM, TEM, tensile testing, and tribological tests. The results showed that the FSLW process homogenized the distribution of SiC particle reinforcements in the SiC_p/Al–Fe–V–Si composites. The Al₁₂(Fe,V)₃Si heat-resistant phase was not decomposed or coarsened, and the mechanical properties were maintained. The FSLW process refined the grains of the ZL101 aluminum alloy through recrystallization and fragmented eutectic silicon, improving elongation to 22%. A metallurgical bond formed at the joint interface. Tensile fracture occurred within the ZL101 matrix, demonstrating that the interfacial bond strength exceeded the alloy’s load-bearing capacity. In addition, the composites exhibited significantly enhanced wear resistance after FSLW, with their wear rate reduced by approximately 40% compared to the as-received materials, which was attributed to the homogenized SiC particle distribution and the activation of an oxidative wear mechanism. Full article

An approach for the formation of intermetallic coatings on the titanium surface based on titanium aluminides is proposed. The approach involves producing a layered steel-aluminum-titanium metal composite via explosive welding, followed by heat treatment to form a diffusion zone at the steel–aluminum interface with a thickness of more than 30 μm, sufficient for the spontaneous separation of the steel layer. As a result, an aluminum layer approximately 0.3 mm thick remains on the titanium surface. Subsequent heating at temperatures of 700–850 °C, below the allotropic transformation temperature of titanium, results in the transformation of the aluminum layer into titanium aluminides. The formation of the intermetallic coating structure occurs as a result of the upward transportation of TiAl₃ fragments separated from the reaction zone by circulating melt flows. With increasing heat treatment time, these fragments become separated by the Al₂O₃ oxide phase. Full article

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

Resistance spot welding was performed to join a 2 mm thick TA2 titanium plate and Q235 steel plate using nickel foil with thicknesses of 0.02 mm, 0.04 mm, and 0.06 mm as interlayers. The microstructure of the nugget zone and the interface region of the joint were systematically observed and analyzed, and the tensile shear-bearing capacity of the joint was evaluated. As the welding current increased, the tensile shear load of the joint exhibited a trend of initially increasing and subsequently decreasing. When the welding current was 8 kA, the tensile shear load of the joints with an interlayer of 0.04 mm thickness reached a maximum value of 8.02 kN. The results indicate that employing a reduced welding current can effectively prevent the mixing of nuggets on both sides of the titanium and steel interface. This ensures that the intermetallic compounds formed in the interface region are confined to the Ti-Ni series, which is crucial for enhancing the tensile shear load of the joint. Full article

The incorporation of multi-material design (MMD) to achieve lightweight vehicles requires Friction Stir Spot Welding (FSSW) to join steel with aluminum, magnesium, or composites. This study investigates the mechanisms, challenges, and performance of FSSW in MMD based on the information available in the literature. It also explores the effect of FSSW tool geometries and design on the spot weld formation and mechanical strength. Larger shoulder and pin diameters increase heat generation during welding. A concave shoulder profile produces a stronger weld compared to flat and convex profiles due to its ability to trap materials and transfer materials to the sheet interface efficiently for the development of a sound weld. Grooves such as Fibonacci and involute, and threads on P-FSSW and R-FSSW tools, also contribute to effective material flow during welding, hence assisting in heat generation. This review also provides recommendations on tool design for FSSW, P-FSSW, and R-FSSW. Full article

Traditional industrial robot programming methods often pose high usage thresholds due to their inherent complexity and lack of standardization. Manufacturers typically employ proprietary programming languages or user interfaces, resulting in steep learning curves and limited interoperability. Moreover, conventional systems generally lack capabilities for remote control and real-time status monitoring. In this study, a novel approach is proposed by integrating digital twin technology with traditional robot control methodologies to establish a virtual–real mapping architecture. A high-precision and efficient digital twin-based control platform for industrial robots is developed using the Unity3D (2022.3.53f1c1) engine, offering enhanced visualization, interaction, and system adaptability. The high-precision twin environment is constructed from the three dimensions of the physical layer, digital layer, and information fusion layer. The system adopts the socket communication mechanism based on TCP/IP protocol to realize the real-time acquisition of robot state information and the synchronous issuance of control commands, and constructs the virtual–real bidirectional mapping mechanism. The Unity3D platform is integrated to develop a visual human–computer interaction interface, and the user-oriented graphical interface and modular command system effectively reduce the threshold of robot use. A spatially curved part welding experiment is carried out to verify the adaptability and control accuracy of the system in complex trajectory tracking and flexible welding tasks, and the experimental results show that the system has high accuracy as well as good interactivity and stability. Full article

This study presents a novel flake powder metallurgy approach for fabricating Al/CNT composites, combining the dual-matrix (DM) method with shift-speed ball milling (SSBM) to optimize mechanical performance. Samples prepared via DM-SSBM were systematically compared to those produced by conventional high-speed ball milling (HSBM), single-stage SSBM, and dual-matrix (DM) routes. Tensile testing revealed that the DM₁MR₅₀-SSBM composite achieved a superior balance of strength and ductility, with an ultimate tensile strength of ~267 MPa, elongation of ~9.9%, and the highest energy absorption capacity (~23.4 MJ/m³) among all tested samples. In contrast, the HSBM sample, while achieving the highest tensile strength (~328 MPa), exhibited limited elongation (~4.7%), resulting in lower overall toughness. The enhanced mechanical response of the DM-SSBM composites is attributed to improved CNT dispersion, refined cold-welding interfaces, and pure Al matrix softness, which together facilitate superior load transfer and hinder crack propagation under tensile stress. In the final consolidated state, aluminum forms a continuous matrix embedding the CNTs, justifying the use of the term “aluminum matrix” to describe the composite structure. These findings highlight the DM-SSBM approach as a promising method for developing lightweight, high-toughness aluminum composites suitable for energy-absorbing structural applications. Full article

Introduction: Cold welding is an anecdotally well-known complication of removal of metalwork, most commonly at the screw–plate interface, and can often complicate extraction of implants after fracture fixation. Even though this phenomenon is familiar amongst the orthopedic community, there is relatively little formalized discussion or literature pertaining to its identification and management clinically. In addition, as far as we can establish, there does not seem to be a paper that discusses the various techniques described in the literature that are employed to combat cold welding. Methods: A systematic review was carried out in accordance with the PRISMA guidance, with two independent reviewers and a third person to arbitrate for any discrepancies. Manuscripts were identified using a search of PubMed/MEDLINE and Google Scholar. Studies eligible for inclusion were tabulated and the results categorized qualitatively with respect to the technique described for removal of the implants. Results: A total of 272 manuscripts were identified using a search of PubMed/MEDLINE and Google Scholar, and of these 14 were ruled to be eligible for inclusion reporting on 292 patients. Common locations of the cold-welded screws included femur, tibia, distal radius and clavicle. The most common technique for metalwork removal was using either bolt cutters or burrs to cut the plates between the screws and mobilize the screw and plate as one unit. Other techniques included using specialized removal tools and cutting between the screw head and body. There was no appreciable correlation between the specific anatomic location of the welded implant and the technique used in its removal. From the studies, it was found that, of the total number of screws (n = 1654), 58 (3.5%) were cold welded. The mean time to metalwork removal was 1104 days (36.8 months). Conclusions: As far as we can tell, this is the first systematic review pertaining to the phenomenon of cold welding specifically, and with this project we have collated the techniques used to remove implants affected by cold welding from a variety of different articles. Our work aims to highlight the relative paucity of literature in this area and provide a number of accessible and safe techniques to facilitate the removal of cold-welded implants in fracture fixation. Full article

With the rise of digital twin technology, the application of digital twin technology to industrial automation provides a new direction for the digital transformation of the global smart manufacturing industry. In order to further improve production efficiency, as well as realize enterprise digital empowerment, this paper takes a welding robot arm as the research object and constructs a welding robot arm digital twin system. Using three-dimensional modeling technology and model rendering, the welding robot arm digital twin simulation environment was built. Parent–child hierarchy and particle effects were used to truly restore the movement characteristics of the robot arm and the welding effect, with the help of TCP communication and Bluetooth communication to realize data transmission between the virtual segment and the physical end. A variety of UI components were used to design the human–machine interaction interface of the digital twin system, ultimately realizing the data-driven digital twin system. Finally, according to the digital twin maturity model constructed by Prof. Tao Fei’s team, the system was scored using five dimensions and 19 evaluation factors. After testing the system, we found that the combination of digital twin technology and automation is feasible and achieves the expected results. 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

Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in detail. The wetting and spreading effect of the ER4043 filler wire was the best, especially on the weld’s rear surface. Serrated-shaped and rod-like IMCs were generated at the top region of the interface of the joint with ER4043 filler wire, but rod-like IMCs did not appear at the joints with the other filler wires. Only serrated-shaped IMCs appeared in the middle and bottom regions for the three filler wires. The phase compositions of all the IMCs were inferred as being made up of TiAl₃. The average thickness of the IMC layer of joints with the ER5356 and ER2319 filler wires was almost the same and thinner than that of the joint with the ER4043 filler wire. The average thickness was largest in the middle region and smallest in the bottom region for all the joints with the three filler wires. The average microhardness in the weld metal of ER5356, ER4043 and ER2319 filler wires could reach up to 77.7 HV, 91.2 HV and 85.4 HV, respectively. The average tensile strength of joints with the ER5356, ER4043 and ER2319 filler wires was 106 MPa, 238 MPa and 192 MPa, respectively. The tensile samples all fractured at the IMC interface and showed a mixed brittle–ductile fracture feature. These research results could help confirm the appropriate filler wire for the laser–MIG hybrid welding–brazing of Ti/Al dissimilar butt joints. Full article

Ultrasonic welding, as a solid-state connection technology, has attracted considerable attention. The traditional ultrasonic welding sonotrode is not conducive to the study of the bonding mechanism of a straight interface, while the ultrasonic additive sonotrode does not have this problem. In this study, a special ultrasonic welding sonotrode was designed to form the joint, which is identical to ultrasonic additive manufacturing, to reveal its interfacial bonding mechanism between layers. Firstly, the linear metallurgical bonding density (LMD) of the joint is found to be positively correlated with welding time and negatively with welding pressure. Furthermore, the joint interface undergoes recrystallization after intense plastic deformation, with the obstruction of surface deformation by interface block resulting in the formation of a non-straight interface, which is beneficial to the formation of metallurgical bonding. Finally, a new concept of “Interface Block” was proposed, which can be applied to explain the formation of metallurgical bonding at the interface in ultrasonic additive manufacturing. Full article

The tungsten target block is widely used as a target material in spallation neutron sources. However, due to the poor corrosion resistance of tungsten, a corrosion-resistant metal layer needs to be coated on the surface. In this study, Zircaloy-4 coating on tungsten was prepared by hot isostatic pressure diffusion welding in the temperature range of 900 °C to 1400 °C. The microstructure and mechanical properties of the zirconium–tungsten interface were studied. The results show that a clear intermediate diffusion layer was formed at the interfaces, and no obvious defects were found. As the HIP temperature increased from 900 °C to 1400 °C, the thickness of the diffusion layer gradually increased from 0.28 μm to 10.74 μm. Composition and phase structure analysis of the intermediate diffusion layer showed that the main phase of the diffusion layer is ZrW₂. The nanoindentation hardness results near the interface showed that the hardness of the ZrW₂ diffusion layer was significantly higher than that of W and the zirconium alloy, reaching around 17.96 GPa. As the HIP temperature increased, the bonding strength between Zry-4 and W matrix first increased and then decreased, with the highest bonding strength of 83.9 MPa when the HIP temperature was 1000 °C. Full article

Joining steel and Al alloys can fully utilize their advantages for both base metals (BMs) and optimize automobile structures. In this study, the laser welding–brazing technique was utilized to join DP780 steel and aluminum alloy 5754 (AA5754). The mechanical properties, microstructure, and fracture locations of steel–Al joints prepared using different laser spot positions were comparatively investigated. As the proportion of the laser spot on the steel BM increased from 50% to 90%, the tensile–shear strength of the steel–Al welded joint rose from 169 MPa to 241 MPa. Meanwhile, the fracture location of the joint shifted from the interface to the BM of the aluminum alloy. The change in the laser spot position could dramatically affect the interfacial microstructure and fracture mode of the steel–Al joint. When the proportion of the laser spot on the steel BM was relatively small (50%), the growth of intermetallic compounds (IMCs) was inhibited. The metallurgical bonding effect at the steel–Al interface was poor. In this case, the interfacial zone became the primary path for the crack propagation. Thus, interface failure became the dominant failure mode of the steel–Al joint. On the contrary, metallurgical bonding at the interface was remarkably improved as the proportion of the laser spot on the BM of the steel increased (to 90%). It was determined that the IMCs could effectively hinder the propagation of cracks along the interface. Eventually, the joint fractured in the Al alloy’s BM, resulting in a qualified steel–Al joint. Full article

TC4 titanium alloy and 5083 aluminum alloy with different groove shapes were joined by laser-MIG hybrid welding–brazing using ER4043 filler wire. The effects of groove shape on the weld formation, intermetallic compounds and tensile property of the Ti/Al butt joints were investigated. The welds without obvious defects could be obtained with grooves of I-shape and V-shape on Ti side, while welds quality with grooves of V-shape on Al side and V-shape on both sides were slightly worse. The interfacial intermetallic compounds (IMCs) on the brazing interface were homogeneous in the joints with groove of V-shape on Ti side, and V-shape on both sides, which had similar thickness and were both composed of TiAl₃. Unlike the IMCs mainly composed of TiAl₃ at the I-shape groove interface, TiAl₃, TiAl, and Ti₃Al constituted the IMCs at the V-shape on Al side interface. The average tensile strength of Ti/Al joints with groove of I-shape was the highest at 238 MPa, and was lowest at 140 MPa with groove of V-shape on Al side. The tensile samples mainly fractured at IMCs interface and the fractured surfaces all exhibited mixed brittle–ductile fracture mode. Based on the above research results, I-shape groove was recommended for laser-arc hybrid welding–brazing of 4 mm thick Ti/Al dissimilar butt joints. Full article