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The reliable connection between ceramics and metals achieved through brazing is a crucial method to promote their application. In this study, the FeCoCrNi high entropy alloys was adopted as the filler to connect SiC and Mo through vacuum brazing. The microstructure evolution and mechanical properties of the SiC/FeCoCrNi/Mo brazed joint at different brazing temperature and holding time were systematically investigated. With the increase of the brazing temperature or the extension of the holding time, the reaction layer gradually thickened with the increasing precipitation of the soft FCC phase. Notably, the FCC solid solution phase with good plastic deformation ability and the brittle Cr 0.46 Mo 0.4 Si 0.14 phase have good interface bonding (lattice mismatch degree ∼ 3.12 %). The dispersive and staggered distribution of FCC phase and Cr 0.46 Mo 0.4 Si 0.14 phase can effectively alleviate the joint stress and hinder crack propagation. This work is expected to provide theoretical guidance for the connection of ceramics and metals through high-entropy alloys. [ABSTRACT FROM AUTHOR]

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al 2 O 3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al 2 O 3) and amorphous Al 2 O 3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue. [ABSTRACT FROM AUTHOR]

As the demand for lightweight structures in the transportation industry continues to rise, AA5083 aluminum alloy has become increasingly prominent due to its superior corrosion resistance and weldability. To facilitate the production of high-quality, intricate AA5083 components, 5087 aluminum filler wire is commonly utilized in metal inert gas (MIG) welding processes for industrial applications. The optimization of filler wire composition is critical to enhancing the mechanical properties of AA5083 MIG-welded joints. This study investigates the effects of modifying 5087 aluminum filler wires with different titanium (Ti) contents on the microstructure and weldability of AA5083 alloy plates using MIG welding. The influence of Ti contents was systematically analyzed through comprehensive characterization techniques. The findings reveal that the constitutional supercooling induced by the Ti element and the formation of Al3Ti facilitate the heterogeneous nucleation of α(Al), thereby promoting grain refinement. When the Ti content of 5087 filler wire is 0.1 wt.%, the grain size of the weld center was 78.48 μm. This microstructural enhancement results in the improved ductility of the AA5083 MIG-welded joints, with a maximum elongation of 16.64% achieved at 0.1 wt.% Ti addition. The hardness of the joints was the lowest in the weld center zone. This study provides critical insights into the role of Ti content in MIG welding and contributes to the advancement of high-performance filler wire formulations. [ABSTRACT FROM AUTHOR]

As a promising high‐thermal‐conductivity ceramics, the direct bonding of Si3N4 with metals remains challenging. Here, we employed active metal brazing of Si3N4 ceramics and Kovar alloys using AgCuTi metal filler, and found that the shear strength in the prepared Kovar/AgCuTi/Si3N4 joints depends on the competitive correlation between the interface layers. The competitive consumption for active element Ti by Kovar/AgCuTi interfacial reactions reduced AgCuTi/Si3N4 interface layer thickness and deteriorated final shear strength, even when using a high‐Ti‐content filler. Surface analysis indicated that interfacial fracture between Ag‐based solid solution and Ti5Si3 was the primary cause of failure. Density functional theory (DFT) revealed that Ag (111)/Fe2Ti (001) interface had higher ideal work of adhesion (Wad) than Ag (111)/Ti5Si3 (001) interface, confirming the importance of AgCuTi/Si3N4 interface layer. Ultimately, by adjusting interface reaction layer thickness, the joints reached a high shear strength of 154.3 MPa. [ABSTRACT FROM AUTHOR]

Desulfurization as a pre-treatment technique, of the transportation fuel is peremptory both for upgrading fuel quality for commercial exploitation and reducing the outflow of poisonous sulfur compounds for environmental remediation. This article encompasses the applications of mixed matrix membranes (MMMs) for the desulfurization of transportation fuels. This composite membrane system synergizes viable processability of the polymers and enhanced selectivity of different incorporated fillers. Hence it offers increased thermal stability, mechanical strength, excellent separation, and purification performance over traditional polymeric and inorganic membranes. These composite materials are widely studied for their potential applications in sensing, catalysis, water purification, gas separation, and adsorption. Herein, different types of MMMs with respect to fillers, chemical compositions and fabrication methods are focused and then systematically compiled and discussed the recent trend for the desulfurization of transportation fuels with profound scientific rationale. Finally, future prospects and room for further advancements in the wider spectrum of MMMs are discussed for better applications and adoptability in the processing of fuel oils. This review will assist the researchers working on the large-scale processing of transportation fuels with a single-point source of knowledge and will save ample amount of time as well as contribute into key future research directions. [ABSTRACT FROM AUTHOR]

The GMAW process with rotating wire is an advance of the conventional GMAW, where the rotational motion of the wire overcomes the main drawback of the sidewall's lack of fusion, thus allowing narrow gap welding with a significant improvement in productivity and cost reduction. However, the literature addressing its potential to substitute the traditional GMAW process in industrial applications is still scarce. This work investigated the microstructure and mechanical properties of an ASTM A 516 Grade 70 steel narrow gap welded joint with 12 mm thickness deposited with higher heat input to provide the deposition of solely two welding passes. The joint was welded in the flat position using a metal cored wire as filler metal, rotation frequency of 1500 rpm, rotation diameter of 3 mm, and average heat input of 3 kJ/mm. After welding, Vickers microhardness, impact Charpy-V, bending, and tension tests were performed to evaluate the mechanical properties of each region of the welded joint, while scanning electron microscopy associated with electron backscattering diffraction techniques was used for the microstructural characterization. The results showed the absence of welding defects and mechanical properties superior to the base metal. Consequently, this process can be suggested as an advantageous alternative to the usual procedures used in industry for welding pressure vessels due to the association of higher productivity and suitable mechanical properties. [ABSTRACT FROM AUTHOR]

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a filler metal. Five oxides (SiO2, TiO2, Fe2O3, Mn2O3, and Cr2O3) have been investigated without edge preparation. The welded joints were evaluated for weld morphology, microstructure, mechanical properties, and corrosion, and the findings were compared. The depth of the AMIG weld was determined to be greater than that of the MIG weld. The microstructure is composed of austenitic and retained delta ferrite with 3.3% for MIG and up to 8% for AMIG weld carried out with Cr2O3 oxide flux, the tensile strength is up to 604 MPa when using Cr2O3 oxide against MIG weld (532 MPa), and the resistance to sudden load in AMIG welds (189 J/cm2) is higher than that of MIG weld (149 J/cm2). The corrosion resistance of the weld made with Fe2O3 oxide flux is greater than that of the other AMIG and MIG welds, as well as the parent metal. The AMIG welding technique variant enhances productivity and decreases the cost and energy consumption of the welding material compared to the traditional MIG process. This allows for joining the same thickness without affecting mechanical properties and corrosion resistance, meeting the industry's requirements. [ABSTRACT FROM AUTHOR]

Melting point depressants (MPDs) are required to lower the melting point of filler for brazing. In this study, Zr was used as the MPD, and powder filler was prepared by adjusting the Zr and Mo content referring to Thermo-Calc calculations. The prepared filler was used to braze a high-Mo Ni3Al-based single crystal superalloy, IC21, for 1200 °C/30 min. The effects of adjusting the Zr and Mo content on the microstructure and tensile properties of the joint were investigated. The increase in Zr content promotes the formation of Ni7Zr2 in the joint, leading to a decrease in the tensile strength of the joint. The increase in Mo content forms diffusion barriers between the BM and filler, resulting in an enhancement in the tensile strength of the joint. However, continued increases in Mo content leads to an increase in the P-topologically close packed phase, causing a decline in the tensile strength of the joint. When the Zr content was (11.8–12.2) wt.% and the Mo content was (7.3–7.7) wt.%, the tensile strength of the joint at 980 °C reached a maximum of 550 MPa. This study provides a potential direction for the design of brazing filler composition for high-Mo Ni3Al-based superalloys. [ABSTRACT FROM AUTHOR]

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In the present study, cold metal transfer arc welding was employed to weld the 304L austenitic stainless steel (ASS) and Ti-stabilized 439 ferritic stainless steel (FSS) using a 309L filler electrode. Dissimilar joints were prepared using low heat input (HI; W1 ~ 247 J/mm) and high HI (W2 ~ 282 J/mm). The solidification mode for both weldments were the ferritic-austenitic mode and the weld zone (WZ) regions of both the weldments consists of columnar austenites, lathy and skeletal ferrite phases. The interfaces between WZ and ASS base metal showed the unmixed zone, whereas a conventional heat-affected zone (HAZ) was formed between the WZ and FSS base metals. The formation of ferrite stringers were observed in the unmixed zone, whereas peppery features of chromium-rich carbides were observed in HAZ. Moreover, electron backscattered diffraction technique was used to distinguish the microstructural differences between W1 and W2 weldments. Increase in the HIs resulted in decreased ferrite fraction in WZ as well as decrease in the mechanical strength of the joints. The W1 weldment depicted higher values of average micro-hardness (WZ ≈ 334.32 HV) than W2 (WZ ≈ 310.92 HV)) weldment. The electrochemical behaviour of the weldments was analysed for both the base metals and WZ of weldments. The higher degree of sensitization (DOS ~ 9.24%) of W1-WZ showed lower intergranular corrosion resistance than W2-WZ (DOS ~ 7.77%), however, the opposite trend was observed for impedance and pitting resistance. [ABSTRACT FROM AUTHOR]

The 45 mm thick plate of 9% Ni steel was successfully butt welded with NiCrMo-4 filler metal adopting the submerged arc welding (SAW) via a multi-layer and multi-pass process. After welding, the weld joints were tested in cryogenic and room temperature, respectively, to reveal the influence of microstructure evolution on fracture toughness. The microstructure of the heat-affected zone (HAZ) was characterized by reversed austenite and tempered martensite like the base metal (BM) after post-weld heat treatment, and the weld metal (WM) was presented by austenite in the form of layered columnar grain region (CGR) and fine equiaxed grain region (FGR). With the decrease in temperature, most of the reversed austenite in 9%Ni steel transformed into martensite, resulting in the plastic deformation ability of 9%Ni steel decreased significantly. Moreover, many microvoids formed in WM during the cryogenic fracture process due to the strength mismatch between precipitates and austenite. Compared to FGR, larger and more densely distributed microvoids in CGR were more likely to aggregate into macrocracks, making CGR the weak region in WM at cryogenic temperature. [ABSTRACT FROM AUTHOR]

This study investigates and establishes the effect of welding process parameters on the tribological performance of the fabricated weld using the gas tungsten arc welding (GTAW) process. Both ER 2594 and ER 70S-2 were used as filler metals to fabricate a dissimilar GTA weld between sDSS 2507 and N50 steels. sDSS 2507/N50 DWJs have substantial importance to the subsea oil-gas drilling industries, especially in tubing and coupler assembly. The thermodynamic study predicts microstructure evolution during weld fusion zone cooling. Dry-sliding tribology behaviors were investigated using a pin-on-disc dry-sliding wear tester with a constant load of 30 N, sliding speeds from 1.111 to 6.666 m/s, and distances from 500 to 3000 m. Scanning electron microscopy examined the worn surface's wear mechanism and progression. ER70S2-LHI specimen had the lowest volume loss (12.83 mm3), and the N50 BM exhibited the greatest (112.65 mm3). Due to its martensitic structure, ER70S2-LHI has the lowest wear rate (4.28 × 10–3 mm3/m), while N50BM demonstrates the highest wear rate (37.5 × 10–3 mm3/m). For both LHI and HHI weld conditions, ER70S2 filler welds outperform ER2594 filler welds by 85 and 60%, respectively, in volume loss and by 81 and 48%, respectively, in wear rate. N50 BM had poorest wear progression and the ER70S2-LHI weld zone the most. Sliding wear on pins from base metal and filler weld zones exhibits mixed-mode abrasive, adhesive, and fatigue wear, producing material removal as spalling and flaking. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the wetting behavior of AgCuTi and AgCu filler metals on selective laser melting (SLMed) Ti/TiB2, and to analyze the microstructure and fracture characteristics of SLMed Ti/TiB2/AgCuTi or AgCu alloy/SLMed Ti/TiB2 brazed joints. The wetting behavior of AgCuTi and AgCu filler metals on the selective laser melted (SLMed) Ti/TiB2 has been studied. The analysis of microstructures and fracture characteristics in vacuum-brazed SLMed Ti/TiB2 substrate, using AgCuTi and AgCu filler metals, has been conducted to elucidate the influence of brazing temperature and alloy composition on the shear strength of the brazed joints. Design/methodology/approach: Brazing SLMed-Ti/TiB2 in a vacuum using AgCuTi and AgCu filler metals, this study aims to explore the optimal parameters for brazed joints at various brazing temperatures (800°C−950°C). Findings: The findings suggest that elevated brazing temperatures lead to a more extensive diffusion region in the joint as a result of the partial melting of the filler metal. The joint composition changes from distinct Ti2Cu layer/TiCu layer/filler metal to a-Ti (ss) + ß-Ti (ss)/TiCu. As the brazing temperature increases, the fracture mode shifts from brittle cleavage to ductile fracture, mainly attributed to a decrease in the CuTi within the brazed joint. This change in fracture behavior indicates an improvement in the ductility and toughness of the joint. Originality/value: The originality of this study lies in the comprehensive analysis of the microstructure and shear strength of vacuum brazing SLMed Ti/TiB2 using AgCuTi and AgCu filler metals. [ABSTRACT FROM AUTHOR]

To solve the technical problems of poor strength–plasticity–toughness matching of titanium alloy welded joints, the optimized multi-stranded wires are used as the filler metal for narrow gap laser welding of TC4 titanium, and the welded joints obtained using high-temperature annealing were heat-treated at 850 °C holding 2 h. The macrostructure, microstructure and texture of both welded joints were compared by employing an optical microscope, scanning electron microscope and transmission electron microscope, and the tensile and impact properties were also evaluated. The results show that after heat treatment of the welded zone acicular α' martensite decomposition into lamellar α-phase + β-phase, the welded joint microhardness distribution tends to be smooth, the average tensile strength of the welded joints is 902 MPa, elongation is 14.5%, about 4.1% lower than the as-welded of the welded joints tensile strength, but elongation increased 3.5%, and room-temperature impact energy is 18.5 J, increased by about 54% than the as-welded impact energy, achieving a reasonable match of strength–plasticity–toughness of titanium alloy welded joints. [ABSTRACT FROM AUTHOR]

Carbon and low-alloy steel plates clad with stainless steel or other metals are a good choice to meet the demand for cost-effective materials to be used in many corrosive environments. Numerous technical solutions are developed for the production of clad steel plates, as well as for their joining by fusion welding. For thick plates, a careful strategy is required in carrying out the multiple passes and in choosing the most suitable filler metals, having to take into account the composition of the base metal and the cladding layer. The specificity of the different processes and materials involved requires an adequate approach in the study of the metallurgical characteristics of clad steel, thus arousing the interest of researchers. Focusing mainly on ferritic steel plates clad with austenitic steel, this article aims to review the scientific literature of recent years which deals with both the production and the fusion welding processes. The metallurgical issues concerning the interfaces and the effects of microstructural characteristics on mechanical behaviour and corrosion resistance will be addressed; in particular, the effects on the fusion and thermally affected zones that form during the fusion welding and weld overlay processes will be analysed and discussed. [ABSTRACT FROM AUTHOR]

Complex liquid–solid reactions occur during brazing. A deep understanding of brazing liquid evolution is therefore of important concern for the bonding between filler and substrates. The joining of gas‐pressure‐sintered silicon nitride (Si3N4) ceramic to oxygen‐free copper (OFC) foil was prepared using Ag–Cu–TiH2 filler at 875°C for 0.5 h. The effect of the Ag:Cu ratio on the interfacial microstructure and peeling strength of the joints was analyzed. The reaction of brazing liquid with Si3N4 ceramic includes reactions with both the β‐Si3N4 and the grain boundary phases (Y–Si–Mg–O–N). The resulting interfacial reaction products include TiN, Ti5Si3, and potential Cu3Ti3O. Based on the phase composition and three‐dimensional morphology of the interfacial reaction products in the Si3N4 ceramic/OFC foil joints, a model for the evolution of the brazing liquid as the reaction proceeds was proposed. Peeling test results indicated that the peeling strength of the joints rises unilaterally with the increase of the Ag:Cu ratio in the filler until reaching the peak value of 24.3 N/mm at the maximum Ag:Cu ratio of 90:10. The mechanisms of the joint peeling fracture were discussed in detail. [ABSTRACT FROM AUTHOR]

In this study, a new method for welding an API 5L X65 steel pipe that is internally clad with Alloy 625 cladding using Alloy 22 and AWS ER100S-G steel was developed. The first and second weld passes were made using Alloy 22 to provide excellent corrosion resistance for the Alloy 625 cladding region. The remaining weld passes were made using 100S-G steel to provide high mechanical strength. The welded joints were evaluated for their microstructure and mechanical properties. No significant solidification defects were found in the welded joints, as confirmed by bending and transverse tensile tests. The yield strength of the welded joint showed that welding was capable of delivering the necessary strength compatible with API 5L X65, X70, and X80 steels for subsequent installation using the reel lay process. The microstructure of the welded joint was complex, with the first two weld passes having a soft Ni-fcc matrix composed mainly of Alloy 22, while the first three 100S-G steel weld passes had a hard martensite matrix. The main region of the welded joint had a soft acicular ferritic matrix. Impact toughness testing showed that the energy absorbed by the notch positioned at the first steel weld pass was better than that for the notch positioned at the steel weld pass without a dilution effect for Alloy 22 (approximately 46 J and 14 J, respectively). The toughness of the weld pass increased due to the high Ni incorporation by dilution with Alloy 22, even at − 15 °C, while the steel weld passes that were not affected by dilution with Alloy 22 exhibited very low energy absorption, which is characteristic of steel materials assessed under conditions below the ductile-to-brittle transition temperature (DBTT). The fracture toughness tests confirmed this result, as the major steel weld passes exhibited brittle features that caused abrupt failure during the test at − 15 °C. [ABSTRACT FROM AUTHOR]

To investigate the effect of Ni-P coating on the interfacial reactions in Cu/Al dissimilar metal brazing, a chemical plating method was employed to nickel plate T2 copper, followed by brazing of the Cu/Al joints using the induction brazing technique with BAl88Si flux-cored filler metal. Scanning electron microscopy and electron backscatter diffraction were utilized for microstructural observation and phase analysis of the joints. Mechanical testing was performed to analyze the influence of the coating on the microstructure and mechanical properties of the Cu/Al joints, while also exploring the interface formation mechanism of different brazing joints during the brazing process. The results reveal the formation of intermetallic compounds Cu9Al4 and CuAl2 at the interface of uncoated joints, whereas intermetallic compounds Al2Ni and Al3Ni are formed at the interface of the coated joints. The tensile strength of uncoated joints reaches to 56.4 MPa, outperforming that of coated joints. Brittle fractures occurre in all joints, with the fracture location transitioning from the interface of CuAl2 and the α-Al solid solution in uncoated joints to the Al3Ni intermetallic compound in coated joints. [ABSTRACT FROM AUTHOR]

Polyurethane-based thin-film composites (PUR-based TFCs) with different carbon fillers, namely, carbon flocs formed by carbon dots (CDs) containing O, N, and F heteroatoms and carbon nanotubes (CNTs), were prepared by hot pressing. The morphology and composition of the carbon fillers were investigated by SEM/EDX. Temperature-programmed desorption mass spectrometry and thermogravimetric analysis revealed that the CNTs have the highest thermostability among the fillers. Microwave studies in the X-band showed that the PUR-based TFCs with the CNTs were characterized by higher reflection losses and lower transmission losses than the PUR-based TFCs with the flocs formed by the studied CDs. [ABSTRACT FROM AUTHOR]

High strength low alloy steels which are having excellent corrosion-resistant properties are called corten steels. In the present investigation, 3 mm thick ASTM A242 Corten steel sheets were welded together using the cold metal transfer (CMT) method based on two welding controllable parameters like welding current and welding speed. The controllable input parameters like welding current and welding speed have been altered to produce joints that have no flaws and a complete depth of weld penetration. The evaluation of the microstructure and weld geometry was performed for the cold metal transfer welded ASTM A242 sheets using ER70S6 filler wire. The experimental design of welding parameters was developed using an orthogonal array of full factorial design. The dominance of acicular ferrite microstructure is visible in the fusion zone. Results from Energy Dispersive x-Ray Analysis (EDAX) show that manganese content is higher and nickel concentration is lower in the weld fusion region. The fusion zone of the CMT welded specimen has the greatest hardness, which was measured at 270.2 HV. Due to the formation of acicular and bainite microstructure in the welding seam, the tensile properties at room temperature (RT) were found to be 589.79 and 405.63 MPa, accordingly. Bend tests additionally confirmed the satisfactory ductility of the welded joint. [ABSTRACT FROM AUTHOR]

Electron beam welding–brazing (EBWB) was applied to join TA2 and 2024Al alloys with Al-Mg filler wire. The effect of gap clearance on interfacial microstructures and mechanical properties of the butt Ti/Al joint was discussed. Three types of intermetallic compound (IMC) layers, including discontinuous cellular shape, continuous serrated shape, and discrete club shape, were presence at the TA2 interface. With the increase of gap clearance, the thickness of the IMC layer increased gradually, and the morphology of IMC layer changed from cellular shape to serrated shape and ultimately to club shape. The IMC layer was mainly TiAl3 compound, while the weld zone (WZ) comprised the predominant α-Al and bits of Al-Cu eutectic. The tensile strength of Ti/Al joint first increased and then decreased with the increased gap clearance. When the gap clearance of the butt configuration was 0.4 mm, the Ti/Al joint 3# exhibited the highest strength (316.4 MPa), about 73.7% of that of the 2024Al matrix, which is due to the formation of a continuous serrated-shaped IMC layer with a thickness of 1.36-2.3 μm. [ABSTRACT FROM AUTHOR]

In order to promote the application of SiC ceramics in nuclear reactor cladding materials, the preparation and application of (Zr-20Cu)-10Nb(wt.%) filler metal for SiC brazing were studied. The microstructure morphologies, phase composition and wettability to SiC ceramics of the filler metal prepared by the suction casting method were evaluated. The results show that the filler metal mainly consists of Cu, β-Zr and a diffusely distributed second phase β-Nb, and it can well wet SiC ceramics. In addition, the effects of brazing temperature (1000-1200 °C) and holding time (10-20 min) on the phase composition, microstructure and properties of SiC joints brazed by Zr-Cu-Nb filler metal were investigated, respectively. During the brazing process, the interfacial reactions occur between the filler metal and SiC to produce ZrC, Zr2Si and CuZr, and increasing the brazing temperature or holding time will promote the interfacial reactions. The effects of brazing temperature on joint properties are more significant compared to holding time. The shear strength of brazed SiC ceramic joints first increases and then decreases with the increase of brazing temperature or holding time, and the maximum shear strength of 101 MPa could be achieved when brazing at 1100 °C for 15 min. [ABSTRACT FROM AUTHOR]

This study proposes a method to enhance the airtightness of the joint between the ZrO2 and Crofer alloy using coating technology. With the aid of vacuum sputtering technology, a titanium–copper alloy layer with a thickness between 1.5 μm and 6 μm was first deposited on the surface of ZrO2 and Crofer, respectively. The chemical composition of the deposited reaction layer was 70.2 Cu and 29.8 Ti in at%. Then, using silver as the base material in the reactive air brazing (RAB) process, we explore the use of this material design to improve the microstructure and reaction mechanism of the joint surface between ceramics and metal, compare the effects of different pretreatment thicknesses on the microstructure, and evaluate its effectiveness through air tightness tests. The results show that a coating of Cu-Ti alloy on the ZrO2 substrate can significantly improve bonding between the Ag filler and ZrO2. The Cu-Ti metallization layer on the ZrO2 substrate is beneficial to the RAB. After the brazing process, the coated Cu-Ti layers form suitable reaction interfaces between the filler, the metal, the filler, and the ceramic. In terms of coating layer thickness, the optimized 3 μm coated Cu-Ti alloy layer is achieved from the experiment. Melting and dissolving the Cu-Ti coated layer into the ZrO2 substrate results in a defect-free interface between the Ag-rich braze and the ZrO2. The air tightness test result shows no leakage under 2 psig at room temperature for 28 h. The pressure condition can still be maintained even under high-temperature conditions of 600 °C for 24 h. [ABSTRACT FROM AUTHOR]

In order to address the issues of excessive brittle intermetallic compounds (IMC) formation in the TC4 brazed joints, two types of novel Ti-Zr-Cu-Ni-Sn amorphous braze fillers were designed. The microstructure and shear strength of the TC4/Ti-Zr-Ni-Cu-Sn/TC4 brazed joints were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and electronic universal materials testing machine. The results show that the optimized Ti35Zr25Ni15Cu20Sn5 braze filler whose chemical composition is closer to the eutectic point possesses a lower melting point compared with the equiatomic Ti23.75Zr23.75Ni23.75Cu23.75Sn5. This was beneficial to the sufficient diffusion of Cu and Ni elements with the base metal during brazing and reduces the residual (Ti,Zr)2(Ni,Cu) content in the joint, which helps to improve the joint performance. The room-temperature and high-temperature shear strength of the TC4 brazed joints using the near eutectic component Ti35Zr25Ni15Cu20Sn5 filler reached a maximum of 472 MPa and 389 MPa at 970 °C/10 min, which was 66% and 48% higher than that of the TC4 joints brazed with the equiatomic Ti23.75Zr23.75Ni23.75Cu23.75Sn5 braze filler. Microstructural evolution and the corresponding mechanical response were in-depth discussed. [ABSTRACT FROM AUTHOR]

Gallium‐based liquid metal (LM) has attracted considerable attention as a promising material for stretchable conductors due to its remarkable combination of deformability and metallic conductivity. However, LM inherently faces challenges such as high surface tension, resistance increase, electrical failure due to leakage, and limited mechanical stability. Recently, researchers have explored the concept of "dividing" bulk LM into microparticles (LMP) as a means of addressing these limitations. Nonetheless, the fabrication of LMP results in inherent electrical insulation, requiring additional activation steps to enable their use as stretchable conductors. In this review, the potential of LMP is discussed as an alternative to bulk LM and explore various methods to generate stable LMP‐based conductors and electrically activate LMP for their implementation in soft and stretchable electronics. [ABSTRACT FROM AUTHOR]

An innovative methodology has been developed to control energy distribution, fluid behavior of the molten pool, and fusion at the sidewall during the process of Gas tungsten arc welding (GTAW) process in a narrow gap with an alternating magnetic field by synchronizing the swing of the filler wire and arc. Utilizing a high-speed camera, we observed that the swinging filler wire ensured a stable transition zone between the molten material and the sidewall, effectively mitigating poor wetting and lack-of-fusion defects along the sidewalls. The synchronized swing of the filler wire and arc significantly enhanced the flow of the molten pool. Increasing the speed of the filler wire swing intensified the erosion caused by the molten pool on the sidewall, thus preventing the occurrence of a lack-of-fusion defect on the sidewall. This occurs because the proximity of the filler metal to the sidewall allows for an adequate accumulation of liquid metal, which, using the heat from the molten pool, induces melting at the sidewall, subsequently resulting in the formation of a concave liquid surface. Moreover, the combined effects of arc pressure, arc shear stress, surface tension, and the momentum provided by the swinging wire caused the molten weld pool to flow toward the sidewall. [ABSTRACT FROM AUTHOR]

The conventional practice of heat-resistant nickel-alloys' brazing involves the utilization of industrial Ni-Cr-(B, Si)-based filler metals. However, employing filler metals within this system results in the formation of brittle compounds, specifically, silicides and borides of nickel, chromium, and other elements. These brittle phases have the potential to diminish the mechanical characteristics of brazed assemblies. This study investigates the feasibility of developing multicomponent high-entropy filler metals for brazing Nibased alloys (specifically, heat-resistant ones) without including boron and silicon in their composition. Utilizing computational methods and the updated Hume-Rothery rules, we identified a promising NiCoCrAl-(Ti, Nb) system. Various thermodynamic parameters are computed, and corresponding dependences on the alloying-components' content are established. The alloying limits of experimental alloys are determined, aligning with the criteria established for high-entropy alloys (HEA). Melting temperatures are calculated, and the liquidus-surface area of the NiCoCrAl-(Ti, Nb) system is delineated. Based on the research findings, it is determined that this alloy possesses a dendritic structure with some amount of eutectic component, and its melting temperature below 1220°C makes it suitable for brazing heatresistant nickel alloys. [ABSTRACT FROM AUTHOR]

Dissimilar welds between ferritic and austenitic stainless steels are widely used in industrial applications. Taking into account the issues inherent to arc welding, such as the high heat input and the need to carry out multiple passes in the case of thick plates, a procedure with two simultaneous laser beams (working in a single pass) and consumable inserts as filler metal has been considered. Particular attention was paid to the choice of the filler metal (composition and amount), as well as welding parameters, which are crucial to obtain the right dilution necessary for a correct chemical composition in the weld zone. The first experimental investigations confirmed the achievement of a good weldability of the dissimilar pair ASTM A387 ferritic/AISI 304L austenitic steel, having ascertained that the microstructure of the weld zone is austenitic with a little amount of residual primary ferrite, which is the best condition to minimize the risk of hot cracking. [ABSTRACT FROM AUTHOR]

This study investigates active filling friction stir repair (AF-FSR) and passive filling friction stir repair (PF-FSR) for repairing AISI 304 stainless steel sheets, focusing on addressing the challenges posed by high melting point metals. The research involved repairing overlapping 2 mm thick sheets with pre-drilled holes of 2, 4, and 6 mm diameters, simulating broken components. Various process parameters, including rotational speed, dwell time, and the use of metal fillers, were tested to evaluate their impact on repair quality. The results demonstrated that PF-FSR provided superior mechanical strength to AF-FSR, particularly for larger pre-hole diameters. PF-FSR achieved higher shear tension strength due to better defect filling and reduced void formation, with shear tension strengths exceeding 25 kN for larger pre-holes and lower variability in strength measurements. AF-FSR was less effective for larger pre-holes, resulting in significant voids and reduced strength. Microstructural analysis revealed that PF-FSR facilitated more efficient material mixing and filling, minimizing unrepaired regions. However, excessive rotational speeds and dwell times in PF-FSR led to deformation and flash formation, highlighting the need for optimal parameter selection. Although further studies are needed, this study confirms the feasibility of FSR techniques for repairing small defects in AISI 304 steels, offering valuable insights for sustainable manufacturing practices in industries such as automotive and aerospace, where efficient and reliable repair methods are critical. [ABSTRACT FROM AUTHOR]

In this study, the theoretical welding parameters influencing porosity formation were examined with the aim of reducing or minimizing porosity levels. An experimental design was implemented using the Taguchi methodology for data analysis, resulting in an L9 orthogonal array matrix of experiments. The welding variables considered in the orthogonal array were peak current, peak time, and frequency. Nine lap welds were performed on CP780 steel using the gas metal arc welding process with pulsed arc (GMAW-P), employing an ER70S-3 electrode as filler metal. The percentage of porosity was determined as a response variable, and the actual heat input was treated as a covariable, thereby identifying the welding parameters with the predicted values. Three repetitions were conducted with the optimal welding parameters to validate the Taguchi prediction. The quality of the welds was assessed through radiographic inspection, and metallographic preparation was performed, revealing the microstructure with 5% Nital for 12 s. The samples were analyzed using an optical microscope, and images were obtained with the collage technique. The results showed that the welding parameters predicted by the Taguchi statistics were favorable for all three predicted welded joints. The maximum percentage of porosity obtained was 19%, which was reduced to 1% using the Taguchi methodology, demonstrating the effectiveness of this statistical tool for process optimization. It was observed that for heat input values of 230 to 250 J/mm, the presence of porosities is dramatically reduced, finding a very small window that allows the gases generated by the burning of zinc to be expelled to the surface. [ABSTRACT FROM AUTHOR]

The work presented in this paper focuses on modeling the welding process to develop a numerical model able to perform a good prediction of welding distortions. The model is developed for a butt welded joint using S235 steel as the base metal and an electrode (AWS E6013) as the filler metal. To assess accuracy, numerical and experimental results are compared. The present work makes it possible to identify the main factors influencing the accuracy of the numerical model, which must be taken into account to obtain satisfactory results. To carry out this analysis, the effect of the mechanical properties of deposited metal and the effect of the deposition process were taken into account. The effect of the variation of the mechanical properties of the filler metal on the distortions is illustrated. The model was developed by using APDL language, and the birth and death technique is used to model the deposition process. Distortion results obtained by numerical models approach properly the experimental measurement. Further analysis of the numerical data reveals considerable fluctuation of the obtained results by modifying the models used to describe the plastic behavior and the work hardening process. Regarding this strong correlation, numerical modeling of the welding process needs a vigilant identification of the work hardening mode appropriate for the used materials. [ABSTRACT FROM AUTHOR]

This study focuses on the kinetic analysis of sigma phase formation in filler metal wires on Super Duplex Stainless Steel (SDSS) and Hyper Duplex Stainless Steel (HDSS). Precipitation data reveal that in the solubilized microstructure, sigma phase kinetics are more prominent in SDSS. This increased susceptibility is attributed to the greater number of nucleation sites, which is facilitated by the larger interface area/volume and the higher chromium content in the ferrite. The difference in interface area/volume is significantly more influential in determining kinetics than the composition difference, with nucleation sites playing a central role. The sigma phase transformation in both materials was modeled using the JMAK kinetic law. The JMAK plots exhibit a transition in kinetic mechanisms, evolving from discontinuous precipitation to diffusion-controlled growth. In SDSS, the JMAK values indicate "grain boundary nucleation after saturation," followed by "thickening of large plates." In contrast, HDSS values point to "grain edge nucleation after saturation," followed by "thickening of large needles." The higher kinetics in SDSS are characterized by a smaller nucleation activation energy of 56.4 kJ/mol, in contrast to HDSS's 490.0 kJ/mol. CALPHAD-based data support the JMAK results, aligning with the maximum kinetics temperature of SDSS (875 °C to 925 °C) and HDSS (900 °C to 925 °C). Therefore, the JMAK sigma phase kinetics effectively describe the experimental data and its dual kinetics behavior, even though CALPHAD-based TTT calculations often overestimate sigma formation. [ABSTRACT FROM AUTHOR]

This study explores the microstructure and corrosion resistance of dissimilar gas tungsten arc (GTA) welds between super duplex stainless steel (sDSS 2507) and nitronic steel (N50) using ER2594 and ER70S-2 filler metals. Scanning electron microscopy (SEM) was utilized for microstructural, compositional, and corroded surface analysis, including rust layer examination. Corrosion resistance was assessed through cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and continuous immersion in a 3.5 wt% NaCl solution. Results indicate that ER2594 demonstrates superior resistance to pitting, which is attributed to a substantial difference in pitting resistance equivalent number. Pitting initiation on the N50/sDSS 2507 base metal side with ER70S2 filler suggests galvanic coupling-induced general corrosion. Weight-loss measurements indicate hindered oxygen diffusion during continuous immersion, controlled by the electrochemical activity of the inner rust layer. Electrochemical tests demonstrate an oxygen-dependent cathodic reduction process, while complete immersion corrosion produces primary corrosion products such as β-FeO(OH), Fe3O4, Fe2O3, and γ-FeO(OH). The corrosion model reveals an oxygen-absorbing mechanism with non-protective rust layers and O2 diffusion control, emphasizing Cl−, O2, and rust layer interactions. This study highlights complex interactions between alloy composition, microstructure, and corrosion resistance to enhance performance, offering significant insights for tubing-couple assembly design in deep-water environments. [ABSTRACT FROM AUTHOR]

Diamond/Cu–Sn–Ti composites as potential super-hard abrasive products were prepared in this work by spark plasma sintering at 1223 K. The effects of Ti content on the wettability, interfacial reaction layer thickness, and wear resistance of the bulk composite changes were systematically studied. The results revealed that when the Ti content was below 5 wt%, completely uncoated and partially coated diamond grains were still observed, indicating insufficient wettability, and the interfacial reaction layer appeared to be thin. When the Ti content was 5 wt%, all diamond grains were completely coated, and a continuous and stable interfacial reaction layer composed of TiC has been generated, in which the thickness reached a peak value of 1.72 μm. However, when the Ti content exceeded 5 wt%, the formation of brittle Cu 41 Sn 11 phases was observed, which led to inferior wear resistance. The minimum weight loss was obtained at 5 wt% Ti content. Meanwhile, through FIB-TEM, confirmed that the interfacial reaction layer was mainly composed of continuous TiC layer adjacent to diamond and discontinuous TiC layer in the filler metal, and constitute the formation of a high strength metallurgical interfacial bonding layer. [ABSTRACT FROM AUTHOR]

In this study, a novel TIP–TIG (TT) automatic welding method was used to weld the girth seams of liquefied natural gas (LNG) tanks composed of 9% nickel steel. The microstructure of the joints was characterized via electron microscopy and x-ray diffraction. The tensile strength and ductility of the joints were evaluated via tensile testing. The low-temperature toughness of the joints was investigated via low-temperature impact testing at - 196 °C. This increased the toughness and strength of the TT-welded joint compared to the corresponding values of joints welded using conventional submerged arc welding (SAW). A comparison with the SAW-welded joints revealed that the TT-welded joint presented high strength and excellent low-temperature toughness, which can be primarily attributed to the low heat input. Compared with SAW, TT welding resulted in a lower joint dilution ratio, smaller heat-affected zone, and lower degree of grain coarsening. In addition to fine austenite, as the joint microstructure and several uniformly distributed carbides in the weld seam. These properties hindered the dislocation slip. However, they promoted precipitation strengthening and grain refinement and provided excellent low-temperature toughness to the TT-welded joints. Notably, TT welding does not require weld-bead cleaning between passes. Additionally, owing to improvements in the degree of automation for TT welding, the welding time can be further matched with that of SAW. TT welding with narrow-gap grooves reduces the required amount of filler metal by more than 50%. Therefore, the TT welding process is significantly advantageous and can replace SAW for girth–seam welding of LNG storage tanks. [ABSTRACT FROM AUTHOR]

In this study, 6061-Al and AZ31-Mg were successfully joined using the contact reaction brazing process without an interlayer under a pressure of 2 MPa and a vacuum of 1 Pa. The study examined the microstructure and mechanical properties of 6061/AZ31 joints, as well as the impact of process parameters including heating mode, cooling rate, heating temperature, and holding time on the joints. The results show that the 6061/AZ31 brazing seam can be divided into two zones: the liquid-phase solidification zone and the diffusion reaction zone. The liquid-phase solidification zone consists of the (α-Mg + Al12Mg17) eutectic organization and precipitation phases distributed therein. The diffusion reaction zone mainly consists of the Al3Mg2 layer in the brazing seam close to the 6061. Fractures in joints mainly occur in the diffusion reaction zone, where the hard and brittle Al3Mg2 layer is located and extends into the liquid-phase solidification zone. Brazing joint quality was better with a cooling rate of 5 °C/s and heating without pre-weld and post-weld holding processes. The highest joint shear strength of 37 MPa was achieved at 445 °C with a holding time of 5 s. The joint exhibited no obvious defects, and the axial shrinkage of the specimen was 0.414 mm, with minimal deformation. [ABSTRACT FROM AUTHOR]

In our work, 0.5 mol.% TiO2 was added to Ag‐xCuO (x = 2, 4, 8 mol.%) fillers whose compositions at 1050°C were in the L2 single liquid phase region, the boundary of the miscible phase region, and the L1+L2 miscible phase region, respectively. The role of TiO2 was derived by comparing the quenching microstructure of the fillers on the Al2O3 ceramics and the effect on the interfacial microstructure and shear strength of the joints before and after the addition of TiO2. The results showed that the TiO2 would dissolve into the CuO‐rich L1 liquid phase of the filler, leading it to spread outside the molten droplet. When brazing with Ag‐4CuO‐0.5TiO2 filler, the CuO at the joint interface almost completely disappeared, and the shear strength of the joint was significantly reduced. In contrast, the joint strength showed a small increase when using Ag‐8CuO‐0.5TiO2 filler, as the excess CuO at the interface of the brazed joint was reduced. When the filler composition was in the L2 single liquid phase region, CuO was diffusely distributed throughout the molten droplet. TiO2 was hardly contacted with CuO and its addition had no significant effect on the interfacial microstructure and the shear strength of the joints. [ABSTRACT FROM AUTHOR]

This study investigates the structure–property relationship in a dissimilar joint between super duplex stainless steel (sDSS 2507) and pipeline steel (X-70) using gas tungsten arc welding and ER2594 filler. Tubing and risers used to transport hydrocarbons are regularly joined using these dissimilar metals. The microstructures of lower heat input (LHI-0.7 kJ/mm) and higher heat input (HHI-1.4 kJ/mm) weldments were examined to understand the influence of heat input on the structure–property relationship. The weldments' mechanical characteristics were tested via hardness, impact, and tensile tests. Base metal and weld zone/interface characterization were studied utilizing optical and scanning electron microscopes with energy-dispersive spectroscopy (EDS). Elemental variation was confirmed by EDS spectra, elemental line mapping, and electron probe microanalysis with wavelength-dispersive spectrometer along the weld interface and weld zone. Significant microstructure variation was observed in X-70 BM at the LHI and HHI weld interfaces. Type II boundary and macro-segregation forms like peninsulas and islands were present in both weldments. In LHI and HHI weldment, duplex microstructure dominates the weld zone cap and filler pass. In the backing pass, duplex microstructure replaces skeletal ferrite, which predominates in the root pass of the HHI weld zone. LHI weldment has an average microhardness of 275 ± 7 HV0.5, while HHI had 285 ± 5 HV0.5. Both weldment's tensile tests revealed that the sample fractured on the weaker X70 BM side. LHI and HHI weldments had 600 MPa and 610 MPa ultimate tensile strengths and 22% and 18% elongation percentages, respectively. LHI weldments (200 ± 7 J, 210 ± 4 J) and HHI weldments (210 ± 5 J, 220 ± 8 J) have lower average impact toughness in cap and root pass than the sDSS 2507 BM (320 ± 3 J) and X-70 BM (300 ± 6 J), respectively. The increase in heat input led to a minimal 2% difference in tensile strength, a notable 10% increase in hardness, and a slight 5% variation in impact toughness between LHI and HHI weldments. Marine and offshore applications may benefit from investigating the sDSS 2507/X-70 DWJ's process parameter selection, thermodynamic analysis, and structure–property relationship. [ABSTRACT FROM AUTHOR]

Due to their low thermal conductivity and high thermal expansion, austenitic chromium‐nickel steels have an increased tendency to distortion during welding. In industrial sectors such as rail vehicle construction, there is a high demand for geometrical precision that is not met by distorted components. Introducing a low transformation temperature (LTT) effect in the weld seam influences the stress distribution, which effects the formation of welding distortion. The low transformation temperature effect is achieved by in situ alloying using commercially available materials. The demonstrators made of stainless steel (X2CrNiN18‐7/1.4318) were welded with a low‐alloy filler metal G4Si1. The low transformation temperature effect is assessed by energy dispersive x‐ray spectroscopy and hardness measurements. The effect on distortion was investigated by measuring the demonstrators with a coordinate measuring system and the results were compared with the reference stainless steel demonstrators with stainless filler metal. The alloying process resulted in a reduction of the alloy content to 14.4 m% chromium and 5 m% nickel and a medium‐high hardness of 361 HV 0.2 to 383 HV 0.2. The low transformation temperature effect achieved leads to a significant reduction in welding distortion of up to 78 % compared to the similar reference demonstrators. [ABSTRACT FROM AUTHOR]

Restrictive operating conditions (even exceeding 700 °C) of materials in advanced ultra super critical (AUSC) power plants and the need to minimize manufacturing and maintenance costs require the production of dissimilar metal welded joints (DMW). Significant differences in the physical and chemical properties of welded materials lead to phenomena that reduce the weldability of the metals used and force the search for solutions that limit unfavorable phenomena, e.g., the use of buttering layers. The study presents a comparison of two types of joints with Alloy 617 (UNS N06617) and ferritic P92 (UNS K92460) steel made using Inconel 82 (ENiCrFe-3) and Inconel 617 (ERNiCrCoMo-1) alloys buttering layer and the corresponding chemical composition of filler metals. All areas of the joints made with the gas tungsten arc welding process were subjected to structural investigations (optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) and mechanical tests (microhardness, room and high temperature tensile, and toughness testing). Despite the more complicated welding procedure, sound welded joints were obtained with favorable properties resulting, inter alia, from the reduced thickness of the martensite layer in HAZ of P92 steel and the limited diffusion of alloy components compared to welded joints without the buttering layer. This also resulted in a reduction of the maximum hardness (especially in the case of Inconel 82 buttering—by 15–30 HV0.5 in comparison with Inconel 617 buttering) and an increase in strength while limiting the decrease in plasticity (even 663 MPa tensile strength and 21% of elongation for Inconel 617 buttered joint). Moreover, improved high-temperature performance (approximately 70–100 MPa) of the welded joint following the application of the buttering layer was confirmed. The presented results allow for drawing general conclusions that both proposed welding procedures can be recommended for use in the working conditions occurring at AUSC. [ABSTRACT FROM AUTHOR]

This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal and surrounding areas of the base metal near welded joints. The evolving inelastic strain rate with reformed austenite led to defining two distinct flow rules in the pure martensitic (α′) and austenitic (γ) phases. A linear rule of mixture was then applied to assess global effective stress based on the inelastic strain rate and current austenite fraction during the PWHT. A unified constitutive model incorporating drag stress and back stress, evolving with creep and plastic deformation mechanisms during the PWHT, described the stress–strain behavior. To validate this analysis, a third flow rule was determined in the 18% tempered austenitic microstructure, compared with the rule of mixture's effective stress contribution from each phase on the inelastic strain rate. Isothermal constant strain rate tests in stabilized crystalline microstructures evaluated constants specific to their respective flow rules. This study demonstrates the stability of reformed austenite at elevated temperatures during slow cooling and its significant influence on the mechanical properties of 13Cr-4Ni steels. The effectiveness of estimating yield stress using the rule of mixture based on individual phase behaviors is also confirmed. [ABSTRACT FROM AUTHOR]

With the change of seasons, the shear strength of saline soil subgrade filler will change with the change of external temperature, which will aggravate the adverse effects of seismic on the subgrade. To explore the influence of seismic action on the stability of saline soil subgrade under the influence of temperature on the strength of saline soil subgrade filler, this paper first carried out saline soil shear tests at different temperatures to obtain the in- fluence of temperature on the shear strength of saline soil. Then, the temperature field of the saline soil subgrade was simulated, and then based on the subgrade isothermal stratification model and FLAC3D, the displacement and acceleration amplification effects of seismic action on the shady slope, sunny slope and subgrade of saline soil subgrade in different months were analyzed. The following conclusions were finally drawn: under the action of seismic, In the process of the change of subgrade temperature of Qarhan - Golmud Expressway between -7.7 °C and 27 °C, the change of saline soil cohesion is the main factor affecting the stability of subgrade slope, and the maximum and minimum values of subgrade surface settlement appear in September and June of each year, respectively. In August, the differences of settlement between the shady slope and the sunny slope shoulder of the subgrade were the largest, and the acceleration of the shady slope and the sunny slope and the inside of the subgrade changed most significantly in the vertical direction. Special attention should be paid to the seismic early warning in the above key months; In the range from both sides of the shoulder to the centerline of the roadbed, the acceleration amplification effect starts to increase significantly from about 3m from the centerline of the roadbed to the centerline, so it is necessary to pay attention to the seismic design of this range. [ABSTRACT FROM AUTHOR]

The paper deals in depth with characterizing bead-on-plate welds on EN-GJS-500-14 base metal, utilizing two filler metals: a pure Ni wire and a NiFe wire containing 45 wt pct Ni. The welds were conducted using the same heat input to ensure comparability in microstructure analysis. The microstructural observations were carried out using optical and scanning electron microscopies, X-ray tomography, X-ray diffraction analysis, and microhardness testing. Thermodynamic simulations using the non-equilibrium Scheil solidification model provide insights into the solidification process and the underlying metallurgical factors associated with the observed microstructural evolution. The observations revealed that the pure Ni wire deposited a softer fusion zone with graphite precipitation, while cementite precipitated in the fusion zone of NiFe alloy. The formation of martensite structures with different morphologies was the predominant microstructural evolution in the heat-affected zone of both welds. The partially melted zone of the pure Ni weld is narrower than the NiFe weld because more diffusion of Ni avoids widening the brittle structures in the partially melted zone. An unmixed zone in the form of a peninsula was exclusively observed in the fusion zone of the NiFe weld because of inadequate diffusion of Ni into the liquified materials along the fusion boundary. [ABSTRACT FROM AUTHOR]

In this study, an austenitic CrMnNi–N steel is examined with regard to its solidification behavior of the weld metal. For this purpose, the cooling rate of the weld metal at different welding speeds is determined for tungsten inert gas welding without filler metal. The relationship between secondary dendrite arm spacing (λ2$\left(\lambda\right)_{2}$) and cooling rate (ε.$\overset{.}{\epsilon}$) can be described using λ2=18.56⋅ε.−0.269$\left(\lambda\right)_{2} = 18.56 \cdot \left(\overset{.}{\epsilon}\right)^{- 0.269}$. Moreover, the microstructure is characterized by a scanning electron microscope using energy‐dispersive X‐ray spectroscopy (EDS). Based on the EDS measurement, it is possible to describe the microsegregation of Cr, Ni, Mn, Mo, and N. The detected microsegregation behavior is compared with the results obtained from Thermo‐Calc calculations. The microsegregation varies depending on the present phase during solidification and correlate well with microstructure observations. By using the software Thermo‐Calc, the theoretical description of solidification is based on the classical Scheil model with fast diffusion of N. A primary ferritic solidification is calculated, which correlates with the experimental findings. [ABSTRACT FROM AUTHOR]

Corrosion behavior is critical to the application of lightweight aluminum/steel joints using new resistance spot welding (RSW) technology. The study investigated the corrosion mechanism and the shear strength of RSW joints comprising 1.2 mm 5182 aluminum and 1.5 mm DP780 galvanized steel. Electrochemical corrosion tests were conducted on the base materials and various positions of the welds in a 3.5% NaCl solution. This result revealed that the corrosion susceptibility of the interfacial intermetallic compound (IMC) layer was not accelerated by the aluminum nugget because of the noble corrosion potential. Subsequently, the spray acceleration test was employed to investigate the corrosion mechanism. It is noteworthy that microcracks, as well as regions enriched with silicon and oxygen at the interface front, are preferential to corrosion during salt spray exposure, instead of the IMC layer. Moreover, the shear strength of the joints decreases with the reduction in the effective joint area after the salt spray exposure of the weld joints. This research systematically explored the corrosion behavior and its relationship with the mechanical properties of Al alloy/steel RSW joints. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]

The present study investigates the tribological behavior and residual stresses of sDSS 2507/X-70 dissimilar weld joints, focusing on their structural integrity for marine applications. Gas tungsten arc welding was performed using ER2594 and ER309L filler metals at lower heat input (LHI-0.7 kJ/mm) and higher heat input (HHI-1.4 kJ/mm). Utilizing a slurry pot tester with varying silica sand concentrations (10 and 30 wt pct), weight loss, erosion wear, and wear mechanisms are analyzed in marine environment. The investigation provides a comprehensive understanding of erosive behaviors by analyzing surface and microstructure characteristics using scanning electron microscopy. All specimens experienced significant weight loss in response to increasing slurry concentrations. Weight loss increased by 17 pct for sDSS 2507 base metal (BM) and 36 pct for X-70 BM with increased slurry concentration. High slurry concentrations induce significant weight loss due to sand particle density, particle-to-surface contact, particle interactions, and fluid impacts. ER309L-LHI lost 55 pct more weight than ER2594-LHI in response to increased slurry concentration, while ER309L-HHI lost 56 pct more weight than ER2594-HHI. Compared to both BM, ER2594-LHI and ER309L-LHI exhibit superior resistance to slurry erosion. ER2594-LHI and ER309L-LHI erosion rates increased 1.14 and 1.32 times with slurry concentration. Material removal mechanisms included micro-cutting, crater formation, lip fragmentation, and ridge formation. Deep-hole drilling method has been used to estimate the residual stress in the weld zone. ER2594 weldment exhibited predominantly tensile residual stress distributed throughout its thickness. The weld surface experienced a longitudinal residual tensile stress of 241 MPa, with the lowest residual stress observed at the weld root. In the ER309L weldment, the maximum residual stress recorded was 175 MPa. The study recommends suitable welding parameters in terms of heat input and filler metals (ER2594 and ER309L) for improved slurry erosion resistance in sDSS 2507/X-70 welds, highlighting the significance of residual stress analysis to evaluate weld structural integrity under operational conditions. [ABSTRACT FROM AUTHOR]