Search Results (668)

The connection between dissimilar materials, Ti and steel, has been a focal point for global scholars. Establishing a high-strength bond between Ti alloy and stainless steel offers the potential to harness their respective advantages and reduce production costs, holding significant applications and far-reaching implications. Currently, non-transition welding methods for Ti/steel, primarily diffusion welding and vacuum brazing, have been pivotal in the early stages of development. Despite their simplicity and convenience, effectively avoiding the formation of brittle Ti–iron compounds in the weld seam, these methods face challenges such as unwelded defects, posing a risk to the reliability of welded structures under service conditions. This limitation restricts their application in products requiring high reliability. The evolving transition welding process, progressing from a single metal interface layer to a multi-metal interface layer, addresses some of the shortcomings of traditional Ti and steel connections, offering promising application prospects. This article delves into the core issue of selecting interface-layer elements and welding methods. Through an analysis of the metallurgical properties of transition metals in conjunction with Ti and steel, the study investigates the impact of single- or bimetallic elements, such as Cu, V, Nb, and Ni, on preparing interface-layer transition metals. A comprehensive review of existing research on Ti and steel welding is presented, with an emphasis on the metallurgical characteristics of their connection. The influence of element selection and welding processes on the metallurgical features and relevant mechanical properties of the weld metal is systematically analyzed and summarized. Full article

Friction stir welding (FSW) began as a fairly specialized joining method, but over the past three decades it has evolved into something considerably more versatile, a manufacturing platform that now handles complex multi-material assemblies and solid-state additive processes with reasonable reliability. This review follows this evolution, paying particular attention to friction stir additive manufacturing (FSAM) and the persistent difficulties that arise when joining dissimilar systems, such as aluminum to steel or metals to polymers, where the fate of the joint is largely decided by how well the intermetallic compounds are kept under control. Machine learning, artificial intelligence, and high-fidelity numerical models are reducing the reliance on trial-and-error that once dominated parameter selection and defect prediction, bringing FSW closer to the operating principles of Industry 4.0. Hybrid variants, including ultrasonically assisted and underwater FSW, also receive attention here, as they offer researchers finer control over heat generation and plastic flow than the standard process allows. Throughout the study, microstructural observations are directly connected to mechanical results, with the aim of analyzing the current state of solid-state manufacturing and identifying the questions that most urgently need answering. Full article

Welding aluminum (Al) to titanium (Ti) is particularly challenging because of the large differences in their melting points and the tendency to form cavities and brittle intermetallic compounds. Such issues can be mitigated in friction stir welding (FSW) by understanding the underlying mechanisms of microstructural evolution and tensile fracture behavior. In the present study, FSW was carried out on commercially pure Al and commercially pure Ti. X-ray micro-computed tomography results show that the distribution of Ti fragments depends on their morphology, with fine particles (volume 10³–10⁴ µm³) being distributed homogeneously, while large flakes (10⁷–10⁹ µm³) are concentrated near the joint interface. A three-dimensional analysis of Ti fragment distribution was performed to clarify material flow and particle dispersion within the weld nugget. EDS (Energy-Dispersive Spectroscopy) and EPMA (Electron Probe Microanalysis) composition mapping confirmed the formation of AlTi and Al₃Ti intermetallic phases, with Al₃Ti as the dominant phase (consistent with its lower Gibbs free energy of formation). Because Al is the primary element in the matrix and undergoes the highest degree of deformation, its microstructural evolution in Al was examined using Electron Backscatter Diffraction (EBSD). Grain refinement in Al was attributed to continuous dynamic recrystallization (CDRX). Mechanical mixing and intermetallic formation increased the hardness of the weld, while the tensile response corresponded to a joint efficiency of approximately 77%, alone with an 11% improvement in elongation over base Al. The study further establishes a correlation among Ti particle distribution, local microstructural evolution, and the tensile response of the joint. Fractographic analysis indicates a bimodal fracture mechanism, and failure occurred away from the joint interface, indicating a strong joint. To interpret this behavior, a spring-based model was proposed to relate the fracture location and tensile deformation to the spatial variation in microstructure across the welded zones. This approach provides a conceptual framework that is extendable to other dissimilar material systems with spatially varying microstructures. Full article

The Charpy impact resistance of monolithic high-strength and dissimilar structured steel was studied. A gas metal arc welding process was used to fabricate the structured steel by depositing a layer of austenitic stainless steel, followed by a layer of hardfacing material over the high-strength steel plate. ANSYS LS-DYNA^TM was used to simulate pendulum–striker impacts on steel Charpy samples. A Cowper–Symonds constitutive model was employed to capture the strain rate behavior. The corresponding material constitutive model parameters were obtained from the literature for the monolithic materials; an iterative numerical optimization method was used to couple the parameters of the structured steel simulation and experimental results. Numerical simulation results showed close agreement with experimental ones. Simulation is a valuable tool for explaining the fracture mechanism in the Charpy impact test and can be used to efficiently design parts made of structured steel that will be subjected to impacts or high-speed deformations. Full article

Bimetallic steel, as a layered composite material formed by metallurgically bonding two dissimilar metals, combines the excellent corrosion resistance of the cladding layer with the superior mechanical properties (such as high strength and toughness) of the base layer. It has been widely applied in demanding fields like marine engineering, the petrochemical industry, and energy equipment, where comprehensive material performance is critical. This paper provides a structured review of the research progress and application status of bimetallic steel. First, mainstream fabrication techniques, such as explosive welding and roll bonding, along with their effects on interfacial bonding quality, are analyzed. Subsequently, key material characteristics, including welding performance, mechanical properties, and corrosion behavior, are discussed. Furthermore, the component-level bearing performance and failure mechanisms under various loading conditions are evaluated. Finally, by synthesizing existing research, current knowledge gaps in areas like long-term service life assessment, adaptability to extreme environments, and efficient intelligent manufacturing are identified, and future development trends are outlined. This review provides important academic reference and engineering guidance for deepening the understanding of bimetallic steels and promoting their safer, more reliable, and cost-effective application in major engineering projects. Full article

With the widespread application of stainless steel rail vehicles, the resistance spot-welding process between stainless steel and low-carbon steel has become one of the key connection processes in vehicle body manufacturing. However, due to the differences in the material physical properties of these two types of steel, problems such as center offset often occur during the welding process. This study adopts the finite element analysis method to systematically analyze the changes in the force field and the temperature field during the welding process after adding a nickel intermediate layer between the two materials, as well as its impact on the physical properties of the joint. The results of the finite element analysis and the physical experiments show that adding a nickel intermediate layer can effectively suppress the center deviation of the weld nugget, optimize the microstructure of the nugget, improve the continuity of the microhardness distribution, and thereby enhance the joint strength of the spot welding. Full article

Joining dissimilar polymers such as polypropylene (PP) and high-density polyethylene (HDPE) remains a challenge in modern manufacturing due to their incompatible thermal properties and poor interfacial bonding. In this study, a novel hybrid structure was fabricated by laser welding of PP to an HDPE matrix reinforced with 3 wt% carbon nanotubes (CNTs). The CNTs were incorporated via fused filament fabrication (FFF) 3D printing to raise the melting temperature and thermal stability of HDPE, thereby minimizing the thermal mismatch with PP. A pulsed CO₂ laser was used to perform butt welding, and the influences of pulse frequency, welding speed, and laser power on the elastic modulus and tensile properties of the weld samples were thoroughly studied. A response surface design was employed to build predictive models and perform multi-objective optimization. The addition of CNTs, as evidenced by differential scanning calorimetry (DSC), elevated the crystallinity level of HDPE from 48.3% to 53.1% and the melting point from 137.8 to 140.8 °C, making its thermal properties more comparable to those of PP. Observations via scanning electron microscopy (SEM) indicated that when the optimal parameters were applied (pulse frequency: 35 Hz, welding speed: 21 mm/s, and laser power: 49 W), the joint line was defect-free, fully fused, and contained very few voids. At these settings, the model estimated an elastic modulus of 793 MPa and a tensile strength of 49.6 MPa, while confirmation experiments yielded 47.2 MPa and 764.5 MPa, respectively, with relative errors below 5%. The results demonstrate that the combination of CNT-assisted laser welding and RSM-driven optimization effectively resolves the thermal incompatibility of HDPE and PP, thereby facilitating high-quality joining of dissimilar polymers for applications in packaging and automotive fields. Full article

The dissimilar joining of aluminum alloy and carbon fiber-reinforced polymer (CFRP) is critical for lightweight manufacturing in transportation and aerospace sectors, yet it remains challenging due to their substantial differences in physical and chemical properties. This paper systematically reviews friction stir welding (FSW) of aluminum alloy and CFRP, and compares it with laser welding, induction welding, resistance welding, and ultrasonic welding. The comparative analysis indicates that while each alternative process presents distinct limitations in thermal management, heating uniformity, or joint configuration, FSW demonstrates the most balanced overall performance, uniquely combining single-pass long-distance capability, low heat input, and broad industrial applicability. Through systematic parametric analysis, the optimal FSW processing window is quantitatively established as a tool rotation speed of 1200–1500 rpm combined with a traverse speed of 30–50 mm/min. Under these optimized conditions, the CFRP side remains below its thermal degradation threshold of 350 °C, the defect volume fraction is reduced from 12% to below 3%, and the maximum joint tensile strength reaches 78 MPa, representing 65% of the base CFRP strength. The interfacial bonding mechanisms are identified as mechanical interlocking and localized chemical bonding, which however cover only approximately 30% of the interfacial area. Optimization strategies, including surface modification, auxiliary structures, nanoparticle reinforcement, and external field assistance, are evaluated for their effectiveness in improving joint quality. Finally, critical challenges and future research directions toward engineering application are outlined. Full article

The laser welding of incompatible polymers, such as polyvinyl chloride (PVC) and polyamide 66 (PA66), is often constrained by weak interfacial bonding, making it challenging to achieve joint strength that meets engineering requirements. This study proposes a welding reinforcement strategy based on femtosecond laser surface microstructuring regulation. First, high-precision and controllable microgroove structures were fabricated on the PVC surface, and the joint welding strength was significantly enhanced via the macroscopic mechanical interlocking effect. The influence of groove width, depth, spacing, and configuration on welding performance was systematically investigated. Subsequently, combined with fracture morphology characterization and finite element simulation, the interfacial reinforcement mechanism and stress regulation law of the microgroove structures were revealed. The results indicate that under the optimal process parameters (groove width = 70 μm, depth = 70 μm, spacing = 130 μm, welding power = 13 W), the joint with vertical groove structures achieves a maximum shear strength of 15.4 MPa, which is significantly superior to that of untreated joints. Additionally, vertical groove structures yield optimal unidirectional load-bearing strength, while grid groove structures effectively mitigate stress concentration under multidirectional loading, exhibiting better adaptability to complex stress conditions. This work provides a high-precision and versatile process for welding highly incompatible polymer systems, and also offers an important theoretical reference for process optimization and engineering applications of laser transmission welding of dissimilar polymers. Full article

This study investigates the mechanical performance of resistance spot-welded titanium lap joints made of Grade 1 and Grade 5 alloys. Experimental tests were combined with artificial neural network modeling to predict joint load-bearing capacity based on welding current and welding time. Three models were developed for Grade 1/Grade 1, Grade 1/Grade 5, and Grade 5/Grade 5 joints. The mixed Grade 1/Grade 5 joint achieved the highest predictive accuracy, with an R² value of 0.9289. Statistical evaluation confirmed high model reliability, with mean relative errors between four and six percent. The most accurate model was optimized using a genetic algorithm. The algorithm identified an optimal parameter set consisting of a welding current of 2.89 kA and a welding time of five pulses. This configuration produced a predicted load-bearing capacity of 3.2 kN, which meets the required threshold of three kilonewtons. Contour maps showed that the optimal point lies near the boundary of the high-strength region and corresponds to the lowest welding current and shortest welding time that still ensure sufficient joint quality. The results demonstrate that combining neural network modeling with evolutionary optimization is an effective approach for designing efficient welding processes for dissimilar titanium joints. Full article

The increasing demand for reliable and high-performance electric vehicle (EV) batteries requires precise and defect-free welding of battery components. Conventional Gaussian laser beam welding faces challenges such as keyhole instability, spattering, porosity, and brittle intermetallic compound formation, particularly in dissimilar Al-Cu joints. These issues significantly affect the electromechanical performance and durability of battery connections. Beam shaping technology has emerged as a core method for improving weld quality, process stability, and efficiency in laser welding, making laser beam welding increasingly vital for high-volume production of e-mobility components. This review systematically evaluates recent advancements in laser beam shaping for laser welding, especially static beam configurations, such as core-ring profiles, flat top, elliptical, and shaped beams; emphasis has been placed on how altering the intensity distribution influences the challenges associated with conventional welding and emerges as an effective solution to address these challenges. By tailoring the spatial energy distribution, beam shaping improves control of heat input, stabilizes melt pool dynamics, and enhances microstructural uniformity. Static beam shaping, compatible with cost-effective near-infrared continuous-wave laser systems, is already being adopted in industry, whereas dynamic beam shaping remains at an earlier stage of industrial maturity. This review highlights key welding challenges in EV battery manufacturing, evaluates beam shaping strategies as practical solutions, and identifies future research directions for large-scale industrial implementation. Full article

Dissimilar 7075-T6 and 6061-T6 aluminum alloy joints were fabricated using pulsed metal inert gas (P-MIG) welding with ER5356 filler wire. The effects of welding current (224 A, 234 A, and 244 A) on macro-morphology, microstructure, mechanical properties, and corrosion behavior were systematically investigated. As welding current increased, the top and bottom reinforcements first increased and then decreased, reaching maximum values at 234 A, while the front weld width exhibited the opposite trend. The weld zone consisted of equiaxed and dendritic grains, with partial remelting of AlFeMnSi intermetallic compounds observed in the heat-affected zones. The microhardness and tensile strength of the joints followed a similar trend of first decreasing and then increasing with welding current, achieving a maximum tensile strength of 203.9 MPa at 244 A, corresponding to 89.5% of the 6061-T6 base metal strength. Corrosion resistance varied across regions depending on the evaluation method. In intergranular corrosion tests, the 7075-HAZ showed the highest susceptibility due to grain boundary segregation of Mg and Zn. In electrochemical tests, the WZ exhibited the poorest corrosion resistance. For the 7075-HAZ, optimal corrosion resistance was achieved at 234 A, attributed to a stable passive film and uniform precipitate distribution. These findings provide valuable guidance for optimizing P-MIG welding parameters for dissimilar 7075/6061 aluminum alloy joints. Full article

Welding is one of the key joining routes for expanding the engineering applications of dissimilar magnesium alloys. However, after experiencing rapid non-equilibrium heating and cooling cycles, the heat-affected zone (HAZ) of a welded joint tends to undergo grain coarsening as well as dissolution or agglomeration of precipitates, and therefore becomes the region most susceptible to failure. In this study, 3 mm thick sheets machined from AZ61A and AZ80A magnesium alloy hollow sections were joined by metal inert gas welding (MIG). Different ranges of welding heat input were obtained by combining multiple sets of welding parameters, in order to further tailor the HAZ of dissimilar magnesium alloy joints and achieve sound weld quality. The results showed that the joint exhibited the best overall mechanical performance at 523 J·mm⁻¹, with an ultimate tensile strength, yield strength, and elongation of 292 MPa, 172 MPa, and 5.4%, respectively. All fractures occurred in the HAZ on the AZ61A side. Under this condition, the second phases in the HAZ were more finely and uniformly dispersed, with a volume fraction of 3.19%, an average size of 2.51 μm, and a minimum average grain size of 23.65 μm. Full article

This study addresses a persistent challenge in polymer joining: the laser welding of two incompatible thermoplastics, polypropylene (PP) and high-density polyethylene (HDPE). The key innovation lies in modifying HDPE with 3 wt% graphene nanoplatelets (GNPs) via material extrusion (MEX), which raises its melting temperature from 136.8 °C to 138.8 °C and increases crystallinity from 46.9% to 51.4%, as confirmed by differential scanning calorimetry (DSC). This thermal adjustment brings HDPE closer to PP’s melting behavior, enabling effective laser butt welding using a pulsed CO₂ laser. A Box–Behnken design within response surface methodology (RSM) was employed to model the individual and interactive effects of laser power (30–50 W), welding speed (15–25 mm/s), and pulse frequency (25–35 Hz) on the flexural and impact strength of the welded joints. Scanning electron microscopy (SEM) revealed that optimal welding conditions—laser power of 49 W, welding speed of 20 mm/s, and pulse frequency of 35 Hz—produce a defect-free interface with complete polymer chain interdiffusion. Under these optimized conditions, the regression models predicted a flexural strength of 69.7 MPa and an impact strength of 21.9 kJ/m². Confirmation experiments yielded 68.2 MPa and 22.6 kJ/m², with relative errors below 4%, validating the predictive capability of the models. This work demonstrates that GNP-mediated thermal property modification, coupled with statistical process optimization, offers a viable pathway for manufacturing high-performance dissimilar polymer joints for lightweight structural applications. Full article