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As a critical component of a welded structure, the integrity of the welded joint significantly affects the safety and reliability of the structure in service. Therefore, it is essential to investigate the integrity of welded joints. However, given the harshness of standard measurements renders them unsuitable for application to small volume zones, welded structures or in-service structures. In this study, the fracture properties of a Q235 steel butt-welded joint was evaluated by boundary effect modelling (BEM) method and the ball indentation (BI) method. The results demonstrate that the fracture toughness distribution obtained by the two methods are consistent, with the highest fracture toughness in the weld metal, followed by the heat-affected zone and the base metal, and the lowest fracture toughness in the fusion zone, which is in agreement with the results of the metallographic testing. Furthermore, the relative errors of the zones obtained by the ball indentation method and the boundary effect modelling method ranging from 10.16 to 19.05%, which indicates safety margin ought to be considered for employing the BI method to determine fracture properties of in-service structures. [ABSTRACT FROM AUTHOR]

In this work, the results from the electron beam welding of copper and Al6082T6 aluminum alloy with a titanium filler are presented. The influence of the filler on the structure and mechanical properties of the welded joint is studied in comparison with one without filler. The X-ray diffraction (XRD) method was used to obtain the phase composition of the welded joints. Scanning electron microscopy (SEM) was used for the study of the microstructure of the welds. Energy-dispersive X-ray spectroscopy (EDX) was applied to investigate the chemical composition. The mechanical properties were studied by means of microhardness measurements and tensile tests. A three-phase structure was obtained in the fusion zone consisting of an aluminum matrix, an intermetallic compound CuAl2, and pure copper. The application of Ti filler significantly decreased the amount of molten copper introduced in the molten pool and the number of intermetallic compounds (IMCs). This improved the strength of the joint; however, some quantity of IMCs was still present in the zone of fusion (FZ), which reflected the microhardness of the samples. The application of a titanium filler resulted in refining the electron beam weld's structure. The finer structure and the reduced amount of the brittle intermetallic phases has led to an increase in the strength of the joint. [ABSTRACT FROM AUTHOR]

Abstract In this publication, an in-process quality assurance method for electron beam welding based on a structure-borne sound emission test for the detection of weld irregularities arising in the process is presented. For this purpose, different sheet materials, i.e., AISI 304, AZ31 and AlMg3, were welded in a butt-joint and the resulting process noises were recorded by means of two acoustic emission sensors specifically designed for structure-borne sound. During the welding experiments, typical irregularities, e.g. incidence points, pore lines and cracks, were deliberately induced. Subsequently, the recorded acoustic signals were examined with regard to defect-specific abnormalities. Various methods in the time and frequency domain as well as pre-trained machine learning models were used to analyze the acoustic emission data. The results show that the investigated irregularities can be identified and distinguished from other process emissions, eventually enabling a robust means of identification for weld seam irregularities and, thus, opening pathways towards cost-effective in-process quality control.

It is generally difficult to obtain good weld formation and excellent properties in super thick titanium alloy joints via conventional electron beam welding (EBW) methods due to the fact that the melt pool flow becomes more unstable as the plate thickness increases. In this study, electron beam scanning welding (EBSW) was utilized to weld 100 mm Ti–6Al–3Nb–3Zr–1Mo titanium alloy plates to improve the weld formation and impact toughness through the scanning effect. The results revealed that there were spatter and cutting defects on the surface and inner pore defect in the normal EBW joint, which could be effectively eliminated via EBSW. The decrease of the amplitude of the fluid flow rate and the change of the velocity direction were mainly responsible for this. A large amount of lamellar α phase with similar orientation was formed in the fusion zone (FZ) due to the fast cooling rate. The joint coefficient for both EBSW and EBW reached 100%, with the joint tensile strength of ∼840 MPa. The impact energy of the FZ in the EBSW joint was 70.5 J, reaching 210.4% of that of the BM (33.5 J). The impact toughness increase ratio in this study was far larger than those for Ti alloy welds ever reported, which was mainly attributed to that the high angle α colony boundaries with high preferred orientation in the FZ deflected the crack propagation direction. This study provides a reference for the strength-toughness design of EBWed joints of super thick Ti6331 titanium alloy.

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The object of this study was the weld material of a new Ti-6.1Al-6.0Zr-6.3Sn-3.2Mo-1.1Nb1.2Si alloy, which was obtained by electron beam welding. Electron beam welding (EBW) provides rapid melting and cooling with crystallization under significant temperature gradients. For the pseudo α-titanium alloy, this leads to the appearance of significant residual stresses in the joint and determines the specificity of the dispersion decay of the β-phase. Residual stresses are reduced by preliminary heating, removed by heat treatment. Such processing exerts a critical influence on the formation of the structure and phase composition of the weld and the zone of thermal influence of the electron beam; it can form macro defects, undesirable phases, and structural states. The conditions of heat treatment have been determined to bring the welded joint from complex alloyed pseudo α-titanium alloy to the required level of mechanical characteristics. The structure, phase morphology, elemental composition, and mechanical characteristics of welded joints without additional heat treatment have been compared, with preliminary local heating of 400 °C, with additional post-weld local annealing at ТТ=750 °С, tT=4 minutes and sequential annealing in the furnace at ТТ=850 °C, tT=60 minutes. It has been established that a full cycle of heat treatment of a welded joint provides the highest characteristics of strength and plasticity, but local heat treatment also makes it possible to obtain a defect-free joint with satisfactory characteristics for less responsible products. It is shown how heat treatment of pseudo α-titanium alloy makes it possible to get rid of unwanted phase formations (Zr,Ti)5Si3Al and transform them into (Zr,Ti,Nb,Mo)3SiAl. The results are promising for use in the production of aircraft engine parts. [ABSTRACT FROM AUTHOR]

Different alloys can be flexibly combined to meet the performance needs of different parts of the compressor disc by welding process. However, achieving a good combination of dissimilar alloys with different mechanical properties has always been a research difficulty. In this work, a Ti600/Ti 2 AlNb joint was fabricated through electron beam welding and an isothermal forging was used to optimized its microstructure and mechanical performance. The isothermal forging process increases the ultimate tensile strength (UST) and yield strength (YS) of the Ti600/Ti 2 AlNb joint by ∼18 ​%, while ∼2.5 times the ductility. It is indicated that before forging, the Ti600/Ti 2 AlNb joint exhibits a much lower strength than that of Ti600 matrix, whereas the opposite is true after isothermal forging. The isothermal forging broken the coarse columnar grains of Ti600/Ti 2 AlNb joint and render to an equiaxed B2 structure in which the acicular α 2 and O phase are precipitated, resulting a synchronous enhancement of strength and ductility. This work may pave an effective routine for improving the comprehensive mechanical properties of dissimilar metal welding joint. [ABSTRACT FROM AUTHOR]

Due to its high energy intensity and the associated high welding depth, electron beam welding is particularly suitable for welding steel plates with high wall thicknesses. These are used, for example, in offshore wind power systems. However, due to the cooling conditions, the required cold toughness for offshore applications is often not achieved. The aim is to develop S355 ML steels – within the EN10025 4 standard – for welding monopiles for wind turbines. For this purpose, three parameters with different energy input are developed on three steels. The tests are carried out on plates with a wall thickness of 80 mm, whereby a full penetration weld must be achieved. The resulting top and bottom bead of the welds meet the standard DIN EN ISO 13919‐1. The parameters have an energy per unit length of 9.5 kJ mm−1 to 15.5 kJ mm−1. The resulting weld seams have an average width of 5.5 mm to 7.5 mm, and burn‐off of the manganese alloy element is observed, particularly on the top side of the seam. In addition, T8/5 times close to the weld seam of 11 s to 27 s are estimated using a simulation. [ABSTRACT FROM AUTHOR]

The influence of furnace annealing on the structure of cast metal in ingots of 200 mm diameter of the intermetallic Ti-28Al-7Nb-2Mo-2Cr titanium alloy produced by the method of electron beam melting and its welded joints produced by the method of electron beam welding was determined. It was determined that the EBM metal produced from the ingots of 200 mm diameter is satisfactorily welded under the conditions of applying such additional technological measures as preheating and local heat treatment. It is shown that annealing at the temperature of 1260 °C for 10 h led to the formation of a uniform microstructure in the base metal, HAZ and weld metal, decomposition of the duplex structure and absence of regions with a two-phase (γ+α2)-lamellar structure. The room temperature strength of welded joints after annealing is equal to 746 MPa or 98 % of the base metal strength. [ABSTRACT FROM AUTHOR]

Electron beam welding processes have highly accurate control of both spatial and temporal heating profiles which provide unique capabilities in dissimilar metals joining. In this work, electron beam welds were made between commercially pure nickel and iron to determine the effect of fusion zone composition on solidification behavior and microstructure evolution. The weld was made with a beam deflected in a circular pattern to enable joining and promote mixing. The beam traveled at a shallow angle of approximately 1 deg to the joint interface starting in the nickel and finishing in the iron. The shallow angle created a weld with a composition gradient along its 110 mm length. The solidification behavior and final weld microstructure were characterized using both light optical microscopy and scanning electron microscopy. Electron backscatter diffraction was used to determine the phase fractions in the fusion zone. A change in solidification mode from face-centered cubic austenite to body-centered cubic ferrite was observed as a function of fusion zone composition. Weld cross-sections containing 65.5 wt pct Fe and 76.9 wt pct Fe had a two-phase fcc + bcc microstructure. Using the compositions and phase fractions, the two-phase region was estimated to be between 56.4 and 79.7 wt pct Fe. Martensite was observed in cross-sections containing between 76.9 wt pct Fe and 98.1 wt pct Fe, which was confirmed using hardness measurements. [ABSTRACT FROM AUTHOR]

In recent years, there's been a strong focus on enhancing high-strength structural steels (HSSSs), making them tougher, stronger, lighter, and more weldable. However, these steels face challenges like cold cracking sensitivity (CCS) and reduced toughness with higher heat input. Therefore, exploring HSSSs with advanced welding techniques like electron beam welding (EBW) is crucial. EBW known for its innovation and precision, is gaining popularity in HSSSs applications for vehicles, construction industries etc. offering advantages like narrow welds, reduced heat-affected zone (HAZ) and low distortion. It is essential to understand the influence of residual stresses (RS) in HSSSs which ultimately affect structural integrity and fatigue life. Using EBW on HSSSs, coupled with synchrotron XRD for residual stress studies, has great potential to advance this research significantly. In this work, a 15-mm-thick EB-welded joint of S960QL and S960 M steels was used to study the RS. At an energy level of 20 keV, RS data from the synchrotron XRD method and its result on the top of welded joints for both types of steel were compared. S960 M steel showed a longitudinal tensile stress of 250 MPa at the weld toe, approximately 1.8 times higher than the 138 MPa observed in S960QL steel under similar conditions. In transverse stress, S960QL exhibits a higher stress of 279 MPa compared to S960 M 46 MPa at the weld toe, approximately 83% lower. The synchrotron method measured 76% lower LRS for S960QL compared to conventional XRD, while S960 M exhibited 55% lower LRS using the same approach.

The mechanism of pore evolution in vacuum electron beam joints of Mo-14Re alloy has been thoroughly investigated. Microscopic characterization methods, including Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), were employed to explore the evolution mechanism of pore defects at different locations. Weld defects were further characterized using Energy Dispersive Spectroscopy (EDS) and Transmission Electron Microscopy (TEM), providing insights into their formation mechanisms. The findings reveal that pores along grain boundaries are the result of MoO and CO bubble aggregation. Non-equilibrium solidification of the melt triggers chemical reactions, transforming MoO and CO bubbles into MoO3 and C, with lower melting points. MoO3 and C persist in the pores, leading to the formation of grain boundary gas hole defects. On the other hand, intragranular pore defects stem from an abundance of pores within the matrix material. Upon entry of gas from these pores into the molten pool, its escape is impeded due to the intense influence of the molten pool. After the molten pool completes the cooling and solidification process, the gas remains within the crystal, resulting in intragranular pore defects.

The flow characteristics of keyhole and molten pool impact the real-time process stability and seam formation severely in all-position low-power laser MAG hybrid (LP-LMH) welding. To probe into the molten pool's real-time dynamics at various spatial welding positions, the high-speed camera images of metal transfer and molten pool were sensed. Meanwhile, a novel spatial flow model of molten pool was developed, and the functions of spatial position and gravity on the molten pool flow were investigated. The results proved that as the spatial position increases, the location of where droplet striking molten pool changes accordingly, further disturbing the keyhole's stability. Meanwhile, the spatial position seriously affects the molten pool's flow. The driving forces of molten pool flow at various spatial welding positions are basically the same, and gravity affects the overall movement of molten pool, thereby affecting the vortexes and heat transmission inside the molten pool, as reflected in weld penetration. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels are very popular due to their high strength properties, ductility, excellent corrosion resistance and work hardening. This paper presents the test results for joining AISI 316Ti austenitic steel. The technologies used for joining were the most popular welding techniques such as TIG (welding with a non-consumable electrode in the shield of inert gases), MIG (welding with a consumable electrode in the shield of inert gases) as well as high-energy EBW welding (Electron Beam Welding) and plasma PAW (plasma welding). Microstructural examinations in the face, center and root areas of the weld revealed different contents of delta ferrite with skeletal or lathy ferrite morphology. Additionally, the presence of columnar grains at the fusion line and equiaxed grains in the center of the welds was found. Microstructural, X-ray and ferroscope tests showed the presence of different delta ferrite contents depending on the technology used. The highest content of delta ferrite was found in the TIG and PAW connectors, approximately 5%, and the lowest in the EBW connector, approximately 2%. Based on the tests carried out on the mechanical properties, it was found that the highest properties were achieved by the MIG joint (Rm, 616, Rp0.2 = 335 MPa), while the lowest were achieved by the PAW joint (Rm = 576, Rp0.2 = 315 MPa). [ABSTRACT FROM AUTHOR]

To enhance welding quality and performance, preheating and post-heating are usually employed on high-temperature materials, concurrently with welding. This is a novel technique in vacuum chamber electron beam welding (EBW). TC17 and Ti2AlNb alloys are the hot topics in aero-engine parts, and the welding of dissimilar materials is also a broad prospect. To settle welding cracks of Ti2AlNb, EBW with preheating and post-heating was investigated on TC17 and Ti2AlNb dissimilar alloy, which improved the manufacturing technology on high-temperature materials. The dissimilar joint no longer had cracks after preheating, which exhibited excellent welding stability and metallurgical homogeneity, and preheating and annealing had an important effect on mechanical properties. The joint strength after 630 °C annealing is higher than that of TC17 alloy base metal (BM) and other annealing temperatures, reaching 1169 MPa at room temperature and 894 MPa at 450 °C tensile condition. The joint plasticity after 740 °C annealing is equivalent to TC17 BM. EBW with preheating improved the microstructure characteristics and enhanced the plasticity of Ti2AlNb alloy weld and dissimilar joint, which would contribute to the application of Ti2AlNb alloy and Ti2AlNb dissimilar parts. [ABSTRACT FROM AUTHOR]

In this research, the temperature field characteristics and melt flow behaviors of 5A06/6061 aluminum alloy lock-butt joint during the electron beam welding (EBW) process are investigated by numerical simulation involving heat transfer and flow of fluid. The calculated mesh model of the lock-butt joint is established with the computational domain divided into three phases. The rotating Gauss heat source is applied to simulate the electron beam energy loaded on the base metal during the welding process. Immediately, not only the temperature filed distributions on the surface and different sections of the molten pool are analyzed carefully, but the flow behaviors of the liquid metal in the molten pool are studied in detail. The results demonstrate that the asymmetric distribution of the temperature field, keyhole, and molten pool morphology exist constantly during the welding process. Besides, there are asymmetric metal flows on both sides of the molten pool and obvious vortex metal flows near the rear and the surface of the molten pool. The melt flow on the keyhole wall represents diversity including the surrounding, downstream, and upstream flow. Moreover, the corresponding experiment is conducted to verify the accuracy of the established model and the simulation results are in good agreement with the experimental results in this work. [ABSTRACT FROM AUTHOR]

This article provides a roundup of project management news in the UK. It covers various topics such as the completion of a major upgrade program by National Highways to improve motorway safety and reduce congestion. It also mentions the positive news of a 5.7% decrease in UK carbon emissions in 2023, bringing the country closer to its net zero goals. Other projects discussed include the use of gas-fired power stations as backup for renewable energy, the implementation of hydrogen in the National Transmission System, and the government's focus on small modular reactors. The article also highlights Sheffield Forgemasters' use of electron beam welding to reduce time and cost in building a full-scale small modular reactor. However, concerns have been raised by MPs about the government's lack of clarity and timeline for SMR projects, prompting a call for a review by the National Audit Office. Additionally, the TransPennine route between Manchester and York is undergoing a major upgrade as part of the Northern Powerhouse Rail project, which includes electrification, digital signaling, station modifications, and increased line capacity. Lastly, the article mentions plans to recreate the woolly mammoth using gene editing technology, although many scientists are skeptical about the feasibility of the project. [Extracted from the article]

The influence of furnace annealing on the structure of cast metal in 200 mm ingots from intermetallic titanium alloy Ti–28Al–7Nb–2Mo–2Cr produced by electron beam melting and of its welded joints produced by the method of electron beam welding was determined. It is established than the metal of 200 mm Ti–28Al–7Nb–2Cr–2Mo ingots based on titanium aluminide is readily welded under the conditions of application of such technological measures as preheating and local heat treatment. It is shown that annealing at the temperature of 1260 °C for 10 h led to formation of a uniform microstructure in the base metal, HAZ and weld metal, decomposition of the duplex structure and absence of regions with a two-phase (γ+α2)-lamel structure. Room temperature strength of welded joints after annealing is equal to 746 MPa or 98 % of base metal strength. [ABSTRACT FROM AUTHOR]

There is a certain contradiction between the formability and strength of auto parts. In this work, the whole-process processing technology of hot stamping soft steel was designed, and 500 MPa grade mild steel (500HS) with uniform microstructure was prepared. To take into account the strength and formability of hot stamping soft steel, here, based on laser welding technology, 500 MPa grade soft steel, and 1500 MPa grade hard steel are benignly composited, and by adjusting the laser welding speed and heat treatment process, the loss of mechanical properties caused by the weld seam is eliminated. A soft/hard composite steel for automobiles with excellent strength, ductility and formability is obtained. To maintain excellent deformation resistance and bonding force of the weld, the heat-affected zone of 500HS retains part of bainite and pearlite, which is beneficial to the strain compatibility and stress partitioning with the microstructure of the base metal, and the hardness is low. After heat treatment, which helps to transfer the stress concentration effect to the 500HS base metal with strong energy absorption capacity, so that the clad steel has excellent comprehensive mechanical properties. This process is developed based on existing industrialized equipment and has broad application prospects. [ABSTRACT FROM AUTHOR]

In order to address the irregularity of the welding path in aluminum alloy frame joints, this study conducted a numerical simulation of free-path welding. It focuses on the application of the TIG (tungsten inert gas) welding process in aluminum alloy welding, specifically at the intersecting line nodes of welded bicycle frames. The welding simulation was performed on a 6061-T6 aluminum alloy frame. Using a custom heat source subroutine written in Fortran language and integrated into the ABAQUS environment, a detailed numerical simulation study was conducted. The distribution of key fields during the welding process, such as temperature, equivalent stress, and post-weld deformation, were carefully analyzed. Building upon this analysis, the thin-walled TIG welding process was optimized using the response surface method, resulting in the identification of the best welding parameters: a welding current of 240 A, a welding voltage of 20 V, and a welding speed of 11 mm/s. These optimal parameters were successfully implemented in actual welding production, yielding excellent welding results in terms of forming quality. Through experimentation, it was confirmed that the welded parts were completely formed under the optimized process parameters and met the required product standards. Consequently, this research provides valuable theoretical and technical guidance for aluminum alloy bicycle frame welding. [ABSTRACT FROM AUTHOR]

In this work, Zr-Sn-Nb alloy was joined by electron beam welding (EBW). A defect-free Zr-Sn-Nb joint with sound appearance was obtained. The grains in the weld zone (WZ) and heat-affected zone (HAZ) are significantly coarsened. The columnar grains with a maximum grain size of 0.5 mm are distributed in the upper region of the WZ, while the equiaxed grains are almost located in the bottom region of the WZ. The WZ is mainly composed of the dominant α-Zr, α′-Zr and a few β phases. The grain orientation of WZ and HAZ is uniform, indicating that no obvious preferred orientation existed. Coarse grains and fine acicular α′ phases increase the strength of the joint, but reduce the plasticity and toughness of the joint. The tensile strengths of the joints at room temperature (RT) and 375 °C were 438 MPa and 313 MPa, respectively. The RT impact energy of the joint is 18.5 J, which is only 58.3% of the BM. The high purity of the EBW process and unsignificant grain orientation minimizes damage to the corrosion resistance of Zr-Sn-Nb alloy joints. The corrosion weight gain of the joint specimen and the BM specimen were 12.91 mg/dm2 and 12.64 mg/dm2, respectively, and the thicknesses of the cross-section corrosion layer were 12–15 μm and 9–12 μm, respectively. [ABSTRACT FROM AUTHOR]

The paper presents the main directions of development in the field of promising aluminium alloys. New generation alloys with improved chemical composition, technologies of manufacture and heat treatment of semi-finished products are considered. The question of the relationship between the structure of the alloys and their operational properties, the influence of heat treatment modes and alloying on mechanical properties and weldability of aluminium alloys in order to obtain the specified predicted operational properties is highlighted. the results of the use of aluminium alloys in aviation and space technology are described. A review of commercial deformable alloys of Al-Li and Al-Cu-Mn system, and comparative characteristics of weldability of various promising aluminium alloys (1460, V-1469, 1201 and their analogues 2090, 2195, 2219) is conducted. [ABSTRACT FROM AUTHOR]

Vacuum electron-beam welding (EBW) was used to join the precipitation-strengthened GH4169 superalloy and a new nickel-based superalloy IC10 to fabricate the turbine blade discs. In this study, a solid solution (1050 °C/2 h for GH4169 and 1150 °C/2 h for IC10) and different heat-exposure temperatures (650 °C, 750 °C, 950 °C and 1050 °C/200 h, respectively) were used to study the high-temperature tensile properties and microstructure evolution of welded joints; meanwhile, the formation and evolution of the second phases of the joints were analyzed. After EBW, the welded joint exhibited a typical nail morphology, and the fusion zone (FZ) consisted of columnar and cellular structures. During the solidification process of the molten pool, Mo elements are enriched in the dendrites and inter-dendrites, and that of Nb and Ti elements was enriched in the dendrites, which lead to forming a non-uniform distribution of Laves eutectic and MC carbides in the FZ. The microhardness of the FZ gradually increased during thermal exposure at 650 °C and reached 300–320 HV, and the γ′ and γ″ phases were gradually precipitated with size of about 50 nm. Meanwhile, the microhardness of the FZ decreased to 260–280 HV at 750 °C, and the higher temperature resulted in the coarsening of the γ″ phase (with a final size of about 100 nm) and the formation of the acicular δ-phase. At 950 °C and 1050 °C, the microhardness of FZ decreased sharply, reaching up to 170~190 HV and 160~180 HV, respectively. Moreover, the Laves eutectic and MC carbides are dissolved to a greater extent without the formation of γ″ and δ phases; as a result, the absent of γ″ and δ phases are attributed to the significant improvement of segregation at higher temperatures. [ABSTRACT FROM AUTHOR]

Electron beam welding of titanium alloy is easy to get high strength welded joints generally. Due to the lack of ductility and toughness, the joint often becomes a failure, which seriously affects the safety of electron beam welded components. This work is aiming at investigation on the strength and toughness control technology of Ti6Al4V alloy joints by electron beam welding with three filler materials to achieve equal strength matching welded joints with good plasticity. The results showed that the microstructures of three filling material are composed of Widmanstatten microstructure and α. The uniformity of microstructure and microhardness of fusion zone have been studied. The tensile strength and impact toughness have been researched, and the fracture morphology was observed by scanning electron microscopy. The strength of adding pure titanium joints decreased with the increase in the thickness of the joint. At the same thickness, the addition of Al can ensure the increase in plasticity and decrease the strength. Therefore, adding 0.5 mm pure titanium and 1 mm Ti4Al in sheet can obtain the joint with the same strength as the base metal and higher toughness than the base metal, and both fillers can realize the effective control of joint strength and toughness. The uniformity of microstructure and microhardness of joints adding 1 mmTi4Al is better. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties were investigated in a 17.48-mm-thick electron beam-welded (EBW) API 5L X65 steel sheet. Electron beam welding has the advantage of joining thick steel parts in a single pass with a high energy conversion efficiency, low heat input and low warpage. The base metal has elongated bands of ferrite interspersed with pearlite colonies aligned along the rolling direction. After welding, a narrow and fine-grained heat affected zone (HAZ) consists of degenerate pearlite and martensite–austenite (M–A) islands. The microstructure of the fusion zone is coarser than the HAZ and more complex, consisting of lower bainite, Widmanstätten ferrite, acicular ferrite, grain boundary ferrite, and small islands of the M–A constituent. These microstructure changes are minimized when EBW is used and do not significantly affect the mechanical properties of the weld. Results of Charpy V-notch tests for weld beads parallel and perpendicular to the rolling direction met the requirements of the API 5L standard. EBW has proven to be a viable alternative for welding thick plates of advanced steels applied in pipeline construction and assembly. [ABSTRACT FROM AUTHOR]

To investigate the feasibility of spinning the welded aluminum alloys, hot spinning tests were conducted on the electron beam welded (EBWed) 2219 aluminum alloy thick plates at 400 °C and successfully obtained a 2.8 mm curved welded-spun plate with a total thickness reduction of 72 %. The abnormal grain growth (AGG) phenomenon of the base material during hot spinning could be observed due to the reduced pinning effect of the θ-Al2Cu phases and static recrystallization, while the fusion zone exhibited homogeneous recrystallized microstructure. After hot spinning, the yield strength of the base material increased from 89.3 MPa to 133.6 MPa and the yield strength of the joint increased from 93.1 MPa to 134.7 MPa. To further optimize the microstructure and improve the mechanical properties of the spun alloy, the subsequent solid solution and aging treatment were conducted. Most of the coarse θ particles dissolved into the matrix and a large quantity of needle-like θ′ precipitates were generated. The yield strengths of the base material and the joint increased to 213.1 MPa and 216.4 MPa, respectively, which was mainly attributed to the precipitation strengthening of the θ′ precipitates. The comparison between the calculated yield stress and the experimental results showed that the contributions of different strengthening mechanisms in strengths were reliable.

The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were evaluated with respect to micro hardness; yield strength; ultimate tensile strength; ductility; and fatigue at room temperature and at elevated temperatures (200 °C and 250 °C). Metallographic investigation was carried out to characterize the microstructures of different weld types, and fractographic investigation was conducted to relate the effect of defects on fatigue performance. Electron and laser beam welding produced welds with finer microstructure, higher tensile ductility, and better fatigue performance than tungsten inert gas welding and plasma arc welding. Large pores, and pores located close to the specimen surface, were found to be most detrimental to fatigue life. [ABSTRACT FROM AUTHOR]

The objective of this study is development and testing of elements of the technological process of electron beam welding (EBw) of intermetallic alloys of TiAl system, which allows performance of welding, preheating and subsequent local heat treatment of welded joints in one pass in one chamber, that enables preventing defects of the type of cold cracks, due to a controlled cooling rate. The work explains why EBW is exactly the most suitable process for welding titanium-based intermetallic alloys. A welding method is proposed and described in detail, which is performed in the gravity position at cantilever fastening of the samples in a special device, while heat treatment is conducted immediately after completion of the welding process, ensuring an optimal cooling rate of the welded joint. It is found that cold cracking in the intermetallic welded joints is related to a low ductility of as-welded material. A mathematical model was developed for numerical prediction of the temperature field kinetics and stressed state calculation. The model was used as a basis to conduct a computational experiment and to determine the thermal conditions leading to cracking in EBW process. It is shown that the highest level of residual stresses is formed directly after completion of the welding process; it is equal to 350 MPa and is observed in the weld center. In order to prevent cold cracks in welded joints of titanium aluminide samples, a technological measure was proposed, which combines EBW of Ti-44Al-5Nb-3Cr-1.5Zr (at.%) intermetallic with preheating and postweld local heat treatment (LHT). It was numerically shown and experimentally confirmed that application of a distributed source of sample preheating before welding allows creating favorable conditions during welding and at further cooling, namely lowering the tensile stresses. The way the process is implemented and its influence on the stressed state and structure of the produced joints are described in detail. The work gives the modes of EBW of sheet intermetallic alloy with a controlled cooling rate and results of structural and mechanical studies of the welded joints, produced by the proposed technology. [ABSTRACT FROM AUTHOR]

Autogenous dissimilar welding of oxygen-free copper to austenitic stainless steel AISI316 was successfully performed by electron beam welding (EBW) using strategic base metal plate tilt of 22 deg and beam shift. The effect of focus distance, beam current, and travel speed on the tensile strength, percent elongation, and impact strength of the welded joints was investigated. The maximum tensile strength was achieved to be 282 MPa at a focus distance of 20 mm, a beam current of 40 mA, and a travel speed of 400 mm/min. Elemental integrity was examined through a continuous energy-dispersive spectroscopy (EDS) scan across the joint for all the welded samples. It was observed that the concentration of elements Fe, Cr, and Ni increased, and that of Cu decreased from the copper region to stainless steel (SS) in the weld zone. The microstructures and microhardness profile of the welded joint were studied. A lower microhardness value was present in the weld region due to a higher fraction of Cu in the weld compared with that of SS. Thus, the balance of energy over the dissimilar materials effectively allowed autogenous welding of a pair of materials which is challenging to join. [ABSTRACT FROM AUTHOR]

The latent heat transfer during vapour condensation in the condenser section of passive heat transport devices such as the two-phase closed thermosiphon is limited by film condensation. Dropwise condensation provides an increase of the heat transfer coefficient by up to one order of magnitude and can be achieved with a water-repellant surface. The inner surface of pipes made from stainless steel was functionalized by laser surface texturing with ultrashort laser pulses and subsequent storage in a liquid containing long-chained hydrocarbons. The pipes were separated into half-pipes by wire eroding to enable laser texturing of the inner surface, and were then joined by electron beam welding after laser texturing. As a result, superhydrophobic and water-repellent surfaces with a contact angle of 153° were obtained on the inner surface of the pipes with a length of up to 1 m. The functionalized pipes were used in the condenser section of a two-phase closed thermosiphon to demonstrate a heat transfer rate of 0.92 kW at 45 °C, which is approximately three times the heat transfer rate of 0.31 kW of a smooth reference pipe. [ABSTRACT FROM AUTHOR]

Hot-rolled Monel 400 sheets of 2 mm thickness were effectively welded by the automated DC-pulsed gas metal arc welding (DC-pulsed GMAW) process using ERNiCu-7 (NA60) filler. An L9 array has been used in this work to obtain optimal robotic welding parameters to achieve better weld quality. The weldments was subjected to microstructural examinations using optical microscopy. The chemical compounds and elements of the weldments were determined using X-ray diffraction and energy-dispersive analyses. The microhardness and tensile properties of the weldments were evaluated. The corrosion behavior of the base metal and weldments was estimated in service environments by exposing them to a 3.5% NaCl solution using a potentiodynamic polarization method. The weld zone has the highest microhardness value of 154 HV. Monel 400 weldments have lower joint strength and elongation than the base metal. In addition, weldments have a higher corrosion rate (201.1 mm/yr) than base metal (55.64 mm/yr). [ABSTRACT FROM AUTHOR]

The paper focuses on the investigation of the effect of heat input on the microstructure and mechanical properties of welded joints produced by electron beam welding of 4.0 mm-thick AW2099 aluminum-lithium alloy. This type of alloy is intended for application in an airplane fuselage. Information on electron beam welding of such type of materials is up to now is very limited. Non-dendritic equi-axed zone (EQZ) was observed at the heat-affected zone–weld metal interface. The higher heat input (HHI) led to the development of EQZ with a larger width. The thickness of EQZ was non-uniform across the base material thickness. EQZ was characterized by the presence of higher amounts of elements at the grain boundaries due to segregation. Eutectics based on α-aluminum + θ-Al2Cu were detected in those areas. Transmission electron microscopy detected the presence of AlLi and Al2Li3 intermetallic phases in the weld metal. Dissolution of the low-temperature δ'-Al3Li phase was observed by differential scanning calorimetry (DSC). Higher peak temperatures of a thermal cycle were measured during HHI welding. A peak temperature of 451 °C at a distance of 1.5 mm from the weld centerline was measured. The dissolution of precipitate particles caused by a thermal welding cycle resulted in the drop of microhardness in the fusion zone. Mean microhardness was slightly higher in the case of lower heat input (LHI) welding, i.e., 73% of that of the base material. The maximum weld tensile strength reached more than 83.8% of that of base materials. The fracture surface revealed the presence of dimples and bright brittle surfaces along with the microcracks and grain boundary eutectics. [ABSTRACT FROM AUTHOR]

Using GTAW, or tungsten inert gas (TIG) welding, weld penetration is usually lesser than the other arc welding processes. ATIG (Activated-flux TIG) welding can be a good alternative to provide deep penetration, and hence, improved productivity. In this work, 304L SS plate of 8 mm thickness was used as base plate, and a flux with a mixture of SiO2, MnO2 and MoO3 was used as a ternary flux in the ratio of 1:1:2. A 2-factor 3-level response surface methodology of central composite design was considered for designing experimental runs. Back Propagation (BP) type Artificial Neural Networks (ANN) model was developed to assess penetration in ATIG welding by using heat input and pulse frequency as the two process parameters. The ANN chosen has 2-10-1 network structure. Results show that the predicted values through ANN are conforming quite well to the experimentally obtained penetration, and hence, the applicability of ANN. [ABSTRACT FROM AUTHOR]

Plates of 2219 alloy of 40 mm thickness were joined by electron beam welding. The effect of sequence of welding and heat treatment operations on the mechanical properties of the joints and distribution of hardness in the HAZ were studied. It was established that the plates of 2219 alloy that were quenched before welding and artificially aged after welding, have the highest strength. Aging improves the ultimate strength of the joints from 300-315 to 385-395 MPa, and hardness of the weld and HAZ metal increases by 5-10 HRB. In the study of the joint microstructure it was found that a region of high-temperature recovery of the hardened state is located at a distance of about 1.0 mm from the fusion line in the haZ. It is characterized by an increase in hardness after aging to the level of base metal hardness. measuring the welding thermal cycles it was found that the maximum heating temperature of this region is about 590 °C. next the annealing region is located. In this region, a decrease in the metal hardness by 2-3 HRB is observed. for welding speed of 20 mm/s, the HAZ width is about 8 mm. [ABSTRACT FROM AUTHOR]

Autogenous joints of Inconel-718 to AISI-316L sheets produced using the electron beam welding process were subjected to defect analysis by the X-ray computed tomography technique. Such investigations revealed variations in undercut and porosity formation tendencies for change in weld processing conditions. The undercut rate has been found to be effectively reduced for the double-side pass and oscillating beam (infinity pattern) conditions. An increase in welding speed from 750 to 1500 mm/min has resulted in the formation of finer pores and reduced its count by 35%. For the same heat input rate, the double-side pass joint has reported formation of uniformly distributed pores with an 80% reduction in number. Compared to static beam joints, the oscillating beam welds have reported an extensive decrease in porosity content (62–87%) and pore-size distribution. The triangular and infinity patterns have reported a more efficient reduction in porosities and size distribution than other patterns. [ABSTRACT FROM AUTHOR]

Ni-base superalloys are employed to produce parts of aeronautic engines, space vehicles and power plants. During the production process or lifetime of components, cracks may occur which affect their performance. Reliable repairs can be carried out through high-energy density welding techniques. This work investigated laser welding of the directionally solidified IN792 DS superalloy. The characteristics of the original material and their evolution in the base metal, heat-affected zone and melt zone after laser welding in different conditions and post-welding heat treatment were investigated through micro-hardness tests, light and scanning electron microscopy observations. The study allowed to optimize the process parameters and post-welding heat treatment, obtaining joints without macro-defects, such as cracks and pores, and with properties and microstructures of the melt zone like those of base metal. [ABSTRACT FROM AUTHOR]

Dissimilar welding of Inconel 713LC superalloy and high strength AISI 4140 steel was conducted using Electron Beam (EB) welding process. The present research study focuses on the effect of post-weld heat treatment (PWHT) on the produced dissimilar joints' microstructure, mechanical properties and corrosion behavior assessment. PWHT was accomplished at 650°C for 2, 4 and 6 h, following air cooling. The microstructure study was carried out by light optical (LOM) and scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS) analysis. The mechanical behavior of the EB joints was investigated via Vickers hardness testing. For the assessment of the EB joints' corrosion resistance, potentiodynamic polarization tests were performed in 3.5 wt.% NaCl solution, at various temperatures. The corrosion products evaluation was carried out by both x-ray Diffraction (XRD) and scanning electron microscopy (SEM). PWHT leds to the microstructure modification of both Inconel 713LC and AISI 4140 in the dissimilar welding zones. The heat treatment holding time increment resulted in the development of more uniform mechanical response among base metals and fusion/heat affected zones, whereas corrosion resistance became progressively weaker. [ABSTRACT FROM AUTHOR]