Search Results (66)

The inferior electrical conductivity and elevated hardness of AgSnO₂ electrical contact materials have impeded their development. To investigate the effects of Co, Bi, and La doping on the stability and electrical properties of AgSnO₂, this study established interfacial models of doped AgSnO₂ based on first-principles calculations initiated from the atomic structures of constituent materials, subsequently computing electronic structure parameters. The results indicate that doping effectively enhances the interfacial stability and bonding strength of AgSnO₂ and thereby predicted improved electrical contact performance. Doped SnO₂ powders were prepared experimentally using the sol–gel method, and AgSnO₂ contacts were fabricated using high-energy ball milling and powder metallurgy. Testing of wettability and electrical contact properties revealed reductions in arc energy, arcing time, contact resistance, and welding force post-doping. Three-dimensional profilometry and scanning electron microscopy (SEM) were employed to characterize electrical contact surfaces, elucidating the arc erosion mechanism of AgSnO₂ contact materials. Among the doped variants, La-doped electrical contact materials exhibited optimal performance (the lowest interfacial energy was 1.383 eV/Ų and wetting angle was 75.6°). The mutual validation of experiments and simulations confirms the feasibility of the theoretical calculation method. This study provides a novel theoretical method for enhancing the performance of AgSnO₂ electrical contact materials. 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

The quality of manufacturing processes largely depends on applying modern design methods and technologies. Much progress has been made in the field of metallurgy and the physics of welding, including the weld pool hydrodynamics, the surface and volumetric forces of different origins, the modeling of the SP crystallization process, and the structural transformation morphology in SWC. Additionally, attempts have been made to use the normalized parameters of fracture mechanics to evaluate the material SU. The above-mentioned solutions have also been given a more specific character by establishing SINTAP procedures and computational welding mechanics (CWM). This study discusses a universal method for welded joint evaluation according to the most significant criteria and relevant descriptive features. Full article

Powder metallurgy (PM) offers several advantages over conventional melt metallurgy, including improved homogeneity, fine grain size, and pseudo-alloying capabilities. Transitioning from conventional methods to PM can result in significant enhancements in material properties and production efficiency by eliminating unnecessary process steps. Dynamic compaction techniques, such as impulse and explosive compaction, aim to achieve higher powder density without requiring sintering, further improving PM efficiency. Among these techniques, magnetic pulse compaction (MPC) has gained notable interest due to its unique process mechanics and distinct advantages. MPC utilizes the rapid discharge of energy stored in capacitors to generate a pulsed electromagnetic field, which accelerates a tool to compress the powder. This high-speed process is particularly well-suited for compacting complex geometries and finds extensive application in industries such as powder metallurgy, welding, die forging, and advanced material manufacturing. This paper provides an overview of recent advancements and applications of MPC technology, highlighting its capabilities and potential for broader integration into modern manufacturing processes. Full article

This study presents a comprehensive investigation into optimizing Tungsten Inert Gas (TIG) welding parameters to enhance the mechanical performance of the widely used Al-6061 T6 alloy, specifically in a double V joint configuration with a plate thickness of 6 mm, for aerospace applications. The Taguchi method was employed to design the experiments, providing a robust framework for analyzing the influence of the electrical current, voltage, and gas flow rate on weld quality. Additionally, a Grey Relational Analysis (GRA) and an Analysis of Variance (ANOVA) were used to validate the optimal welding parameters and quantify the significance of each factor. The optimized parameters were determined to be an amperage of 180 A, a voltage of 18 V, and a gas flow rate of 10 L/min, resulting in significant improvements of up to 40% in tensile strength and 23% in hardness, demonstrating the effectiveness of the optimized conditions. The findings provide valuable insights into welding metallurgy, offering practical guidelines for enhancing high-performance welded joints in critical industrial applications. This study underscores the potential of combining Taguchi, GRA, and ANOVA methodologies to achieve superior mechanical properties and reliability in welded structures. Full article

The paper presents a comparative study of the erosion wear resistance of WC-10Co4Cr, Cr₃C₂-25NiCr and martensitic stainless steel (SS) coatings deposited onto an AlSi7Mg0.3 (Al) alloy substrate by high-velocity air‒fuel (HVAF) spraying. The influence of the abrasive type (quartz sand or granite gravel), erodent attack angle, thickness, and microhardness of the coatings on their and Al substrate’s wear resistance was comprehensively investigated under dry erosion conditions typical for fan blades. The HVAF-spraying process did not affect the Al substrate’s structure, except for when the near-surface layer was 20‒40 μm thick. This was attributed to the formation of a modified Al-Si eutectic with enhanced microhardness and strength in the near-substrate area. Mechanical characterization revealed significantly higher microhardness values for the cermet WC-10Co4Cr (~12 GPa) and Cr₃C₂-25NiCr (~9 GPa) coatings, while for the SS coating, the value was ~5.7 GPa. Erosion wear tests established that while Cr₃C₂-25NiCr and SS coatings were more sensitive to abrasive type, the WC-10Co4Cr coating exhibited significantly higher wear resistance, outperforming the alternatives by 2‒17 times under high abrasive intensity. These findings highlight the potential of HVAF-sprayed WC-10Co4Cr coatings for extending the service life of AlSi7Mg0.3-based fan blades exposed to erosion wear at normal temperatures. Full article

The objective of this study was to investigate how weld overlays with nickel superalloys are important for the integrity, due the high temperatures and corrosive environments that can be experienced in mineral processing environments, of mining and processing equipment. The Ni-Cr-Mo superalloy Inconel 686 overlays are fabricated through automatic gas metal arc welding with variations in arc voltage and travel speed (i.e., heat input), and they have overlap between adjacent weld tracks for applications in the mining and minerals sector. The impact of variations in the process parameters and the size of the weld overlapping on the dilution, solidification morphology, microsegregation, and microhardness were investigated. Both geometric and chemical composition definitions were used to quantify the extent of the weld dilution. Subsequently, the weld geometry and dilution were correlated with the solidification microstructure and phase transformations. The maximum dilutions were measured to be 13.63% (1/2 overlap, 5.96 kJ·cm⁻¹) and 15.39% (1/3 overlap, 4.77 kJ·cm⁻¹), which shows that less of an overlap increases the dilution level. Scanning electron microscopy and chemical composition analysis revealed that an increase in weld heat input and dilution level led to higher levels of microsegregation for Mo and Cr, as well as the volume fraction of Mo- and Cr-rich phases in the interdendritic/intercellular regions in the overlay layer. Analysis of the weld overlays in the current study revealed strong and unprecedented connections between the weld overlay process conditions, the resultant metallurgy (i.e., dendrite arm spacing, microsegregation, and phase formation), and the hardness of the overlay. It was concluded that the optimal weld overlays in the processing window studied in this investigation were fabricated at mid-level heat inputs (i.e., 4–5 kJ·cm⁻¹) and a 1/2 track overlap. Full article

Dissimilar welds between ferritic and austenitic steels represent a good solution for exploiting the best performance of stainless steels at high and low temperatures and in aggressive environments, while minimizing costs. Therefore, they are widely used in nuclear and petrochemical plants; however, due to the different properties of the steels involved, the welding process can be challenging. Fusion welding can be specifically applied to connect low-carbon or low-alloy steels with high-alloy steels, which have similar melting points. The welding of thick plates can be performed with an electric arc in multiple passes or in a single pass by means of laser beam equipment. Since the microstructure and, consequently, the mechanical properties of the weld are closely related to the composition, the choice of the filler metal and processing parameters, which in turn affect the dilution rate, plays a fundamental role. Numerous technical solutions have been proposed for welding dissimilar steels and much research has developed on welding metallurgy; therefore, this article is aimed at a review of the most recent scientific literature on issues relating to the fusion welding of ferritic/austenitic steels. Two specific sections are dedicated, respectively, to electric arc and laser beam welding; finally, metallurgical issues, related to dilution and thermal field are debated in the discussion section. Full article

In recent years, for the structural characteristics and design requirements of the integral rotor and disc shaft of the integrated engine, the welding quality and mechanical properties of superalloy weldments have received increasing attention. In this paper, inertia friction welding (IFW) of FGH96 alloy was carried out using different welding parameters, and the homogeneous connection of FGH96 alloy hollow bars was successfully realized. The microstructure evolution, mechanical properties and fracture failure of the welded joints at room and high temperatures were investigated. The FGH96 alloy IFW joints were divided into the weld nugget zone (WNZ), the thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ) and the base metal (BM), and there were significant differences in grain structure and distribution of the γ′ phase in each of the characteristic zones. The microhardness and tensile properties of the IFW joints were investigated, and the results showed an “M”-shaped curve in the microhardness distribution, with the lowest point of hardness observed in the HAZ. The tensile test results indicated that the fracture position moved from the BM to the WNZ with the increase in temperature, the microstructure at the fracture changed significantly and the tensile strength decreased from 1512.0 MPa at room temperature to 1201.3 MPa at 750 °C. The difference in the mechanical properties of the joints was mainly attributed to the changes in the dissolution and precipitation of the γ′ phase. Full article

In submerged arc welding, evaluating elemental transfer behaviors is critical for selecting and designing welding materials. Accurate assessment of O, Si, and Mn transfer behavior is essential for ensuring process quality, particularly when silicon-manganese fluxes are applied. Traditional quantification methods, however, focus only on chemical reactions in the weld pool zone, potentially overlooking the cross-zone elemental transfer behavior and leading to significant predictive inaccuracies. This study investigates the CaO-SiO₂-MnO flux, a prevalent silicon-manganese flux, focusing on O, Si, and Mn, which exhibit notable transfer behaviors of O, Si, and Mn. By employing a multi-zone approach and integrating various scientific principles, the research aims to improve the accuracy of predicting elemental transfer behaviors and deepen the understanding of the metallurgical processes in submerged arc welding when silicon-manganese fluxes are employed. The study proposes strategic enhancements to traditional quantification methods, which may offer valuable insights for the improvement of industry standards. This study demonstrates that considering only the local thermodynamic equilibrium of the weld pool zone when quantifying the transfer behavior of elements may lead to predictive errors, especially for easily evaporating metallic elements. By incorporating a cross-zone assessment for submerged arc welding process, i.e., introducing new quantifying parameters (Δ_d and Δ_w), the predictive accuracy of the transfer behavior of elements and their cross-zone actions can be enhanced. Full article

With the development of the pressure vessel industry, high-energy wire welding has a great future. However, this means higher demands on the weldability of pressure vessel steels. Controlling inclusions via oxidative metallurgy is a reliable method of improving the weldability of pressure vessel steels. Hence, in this paper, experimental steels with different Mg element mass fractions were prepared using vacuum metallurgy. Simulated welding for high-heat input welding was carried out using the Gleeble-2000 welding thermal simulation test machine. The inclusions in the welding heat-affected zone (HAZ) in the experimental steels were observed using an optical microscope (OM) and scanning electron microscope (SEM). The compositions of the inclusions were analyzed using an energy-dispersive spectrometer (EDS). The research results indicated that the addition of Mg could increase the number density of the inclusions in the welding HAZ. With the addition of Mg from 0 to 5 wt.%, the total number density of the inclusions increased from 133 to 687 pieces/mm^2, and the number density of the inclusions with a size of 0–5 μm² increased from 122 to 579 pieces/mm². The inclusions in the experimental steel welding HAZ with Mg elements were mainly elliptical composite inclusions composed of (Mg-Zr-O) + MnS. Moreover, MnS precipitated on the surface of the Mg-containing inclusions in the welding HAZ. Intragranular acicular ferrite (IAF) nucleation was primarily induced via the minimum lattice mismatch mechanism, supplemented with stress-strain energy and inert interface energy mechanisms. Full article

Pressure vessel steels are used in the manufacture of tanks for the storage of gases, chemical materials and oil. To meet the increasing production demands, high-wire-energy welding is widely used in the manufacture of pressure vessel steels. This means that the weldability of pressure vessel steels needs to be improved. Therefore, in order to reveal the microalloying effect of Ca in pressure vessel steel, this study took a commonly used pressure vessel steel as the research object, and three groups of experimental steels with different Ca mass fractions were prepared using vacuum metallurgy, controlled rolling and controlled cooling. Welding heat simulation technology was used to simulate the welding heat of experimental steel and the welding heat-affected zone (HAZ) was investigated. The inclusions of the welding HAZ in the experimental steels were observed by using a metallographic microscope and scanning electron microscope (SEM). The mechanism of intragranular acicular ferrite (IAF) nucleation induced by the inclusions containing Ca elements in the welding HAZ of pressure vessel steels was also discussed. The research results show that the addition of Ca increased the number density of effective inclusions in the welding HAZ of the experimental steel up to 535.60 pieces/mm². The addition of the Ca element was beneficial for producing more pinning inclusions in the experimental steel welding HAZ under the experimental conditions, and the inclusions were mainly elliptical oxide complex inclusions of Ca-Si with a size of about 2 μm. Meanwhile, Al₂O₃ and MnS were precipitated. After the addition of Ca elements, Mn-poor regions appeared around the inclusions containing Ca in the welding HAZ. IAF nucleation was mainly induced by the local compositional change mechanism and supplemented by the stress–strain energy mechanism and inert interface energy mechanism. This study provides a valuable reference for optimizing the welding process of pressure vessel steels and is of great importance for understanding the IAF nucleation mechanism of Ca-containing inclusions in the welding HAZ of pressure vessel steels. Full article

This study presents information on the behavior of paint baking (PB) after resistance spot welding of the 5- and 6xxx series aluminum alloys. The weld parameters are optimized, and the weld specimens are baked three times for 20 min at 180 °C to simulate the heat treatments required for paint baking. The mechanical properties of the samples were characterized by using the lap shear test, micro/nanoindentation hardness, and fatigue test. As the mechanical properties of the weld are affected by the characteristics of the heat-affected zone and those of the fusion zone, the microstructure of the cross-sections was also analyzed through optical and electron microscopy. The investigation of the 6xxx series welds showed that the post-processing heat treatment decreased both the strength and the toughness of the weld, which resulted from the reduced hardness of the microstructure. Additionally, the lap shear test indicated that the failure mode for the 6xxx series changed from nugget failure to partial nugget failure after the paint baking process. However, the mechanical properties of the 5xxx welds were not affected as much as the 6xxx series during baking heat treatment. The fatigue test for the 6xxx series showed a different tendency from the lap shear test. Its fatigue properties improved due to an increased elastic modulus after the heat treatment. Full article

The purpose of this study is to investigate the transfer behavior of oxygen during the submerged arc welding process using CaF₂-SiO₂-CaO fluxes. In contrast to previous research that only focused on the final oxygen content in the final weld metal, this study introduces two new parameters, Δ_dO and Δ_wO, to quantify the oxygen transfer in essential regions: the droplet and weld pool zones, respectively. The transfer behavior of oxygen is analyzed by using typical Multi-Zone and equilibrium models. The results indicate that the Multi-Zone model is capable of capturing the metallurgical processes of oxidation and subsequent reduction during the submerged arc welding process. Moreover, the Multi-Zone model demonstrates superior predictive accuracy in estimating oxygen content in the metal compared to the equilibrium model. Based on measured values and metallurgical data, this article analyzes the oxygen transfer mechanism and non-equilibrium state in the submerged arc welding process from both thermodynamic and kinetic perspectives. Then, scientific hypotheses previously put forward are validated and discussed, which may offer valuable insights and practical guidance for flux design. Full article

This paper describes the combination of surface engineering and powder metallurgy to create a coating with improved corrosion resistance and wear properties. A new method has been developed to manufacture corrosion-resistant surface layers on steel substrate with additional carbide reinforcement by employing a polymer-powder slurry forming and sintering. The proposed technology is an innovative alternative to anti-corrosion coatings applied by galvanic, welding or thermal spraying techniques. Two different stainless-steel powders were used in the research. Austenitic 316 L and 430 L ferritic steel powders were selected for comparison. In addition, to improve resistance to abrasive wear, coatings containing an additional mixture of tetra carbides (WC, TaC, TiC, NbC) were applied. The study investigates the effects of using multicomponent polymeric binders, sintering temperature, and atmosphere in the sintering process, as well as the presence of reinforcing precipitation, microstructure and selected surface layer properties. Various techniques such as SEM, EDS, hardness and tensile tests and corrosion resistance analysis are employed to evaluate the characteristics of the developed materials. It has been proven that residual carbon content and nitrogen atmosphere cause the release of hard precipitations and thus affect the higher mechanical properties of the obtained coatings. The tensile test shows that both steels have higher strength after sintering in a nitrogen-rich atmosphere. Nitrogen contributes over 50% more to the tensile strength than an argon-containing atmosphere. Full article