Electron Beam Welding Research Articles

Fatigue inhomogeneity of 140 mm thick TC4 titanium alloy double-sided electron beam welded joints

The microstructure and high-cycle fatigue properties of 140-mm TC4 titanium alloy double-sided electron beam welded joints were studied by stratification along the thickness direction. It was found that the microstructure and properties of the weld zone were obviously inhomogeneity in the direction of thickness, and the overlapping area at the root of the two welds (the second layer of the joint) was the weakest position in the high-cycle fatigue performance of the joint. The larger hardness gradient was an important reason for its weaker than other regions. Microstructure differences was the primary reason for the high hardness of the second layer weld zone. It was found that the difference of heat dissipation conditions was a critical factor for the inhomogeneity of microstructure and mechanical properties along the thickness direction of 140-mm double-sided electron beam welding joint. The research results will provide data support for the application of double-sided electron beam welding technology in aerospace manufacturing.

Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure

Electron beam (EB) welding can efficiently join large-scale components using one single autogenous pass, but it still faces challenges associated with weld-induced distortion and stress. This study investigates EB welding in a low-alloy steel thick-section shell-flange structure for a small modular reactor. A 3D thermal-metallurgical-mechanical model is developed to assess the weld-induced distortion and stress, as well as the strategy to mitigate them. When no restraint is imposed on the circumferential weld plane, an opening and sliding gap develops during the EB welding, which can cause weld defects and even process failure. Restraint through tack welds can effectively mitigate the gapping distortion, but it generates high transient tensile stress in the tack weld. Circumferentially continuous tack weld is preferential over circumferentially discrete tack welds to minimise the tensile stress. The final residual stress is insensitive to the tack-weld restraint, and the stress distribution in the steady-state welding region is broadly similar to that found in plate butt welds. However, concentration of residual stresses with high triaxiality occurs in the weld stop region, with high tensile stresses generated just behind the beam stop location, which cannot be diminished by overlap welding or change of weld stop position. The mechanisms responsible for the distortion and the transient and residual stresses are analysed. This study could provide rational basis for designing weld restraint to control distortion and guiding stress mitigation strategy for crack-susceptible region in EB weldments.

Evolution of microstructure and mechanical properties of vacuum electron beam welded joints in a near beta titanium alloy: Influence of heat treatment

Herein, the two plates of a near beta titanium alloy (Ti55531) with a thickness of 60 mm were welded by vacuum electron beam welding, and full penetration welded joints were obtained. The results show that the welded joint can be divided into weld bond, heat affected zone and base metal. Microstructures of weld bond and heat affected zone are composed of coarse β grains and fine α phases distributed at the β grain boundaries and in the β grains, and the β grains in weld bond are coarser than those in heat affected zone. The solution treatment can reduce the microhardness and improve the impact toughness of different zones of the joint. The tensile strength of the welded joint can be improve to 1129 MPa by solution and aging treatment. The influence of heat treatment on microstructures and mechanical properties of these welded joints were discussed in detailed.

Microstructure evolution and mechanical properties of wrought/wire arc additive manufactured Ti-6Al-4V joints by electron beam welding

Wrought-additive hybrid manufacturing technology effectively combines the advantages of high efficiency of traditional manufacturing and high flexibility of additive manufacturing technology. Mechanical Properties of welded joints is the key to evaluate the performance of parts. In this study, the wire and arc additive manufacturing (WAAM) Ti-6Al-4V alloy was successfully connected with the wrought Ti-6Al-4V plate by electron beam welding (EBW). The effect of welding direction on microstructure and tensile properties of welded joints was studied. The results show that a large amount of needle martensite α’ phases exists in the joint due to the rapid cooling rate. The mechanical properties tests show that compared with the Wrought + SD (Scanning direction) sample, the Wrought + BD (Building direction) sample has higher tensile strength, but lower elongation. All samples fractured at the WAAMed Ti-6Al-4V side, which was related to the initial state of the WAAMed Ti-6Al-4V sample. The experiment also explored the fracture mechanism by TEM, which involved the nucleation, growth of cracks caused by vertical dislocation accumulation at the α/α’ phase interface, and occurrence of the displacement of the α (or α’)/β phase interface caused by the parallel dislocations.

Reduced pressure laser weld comparison to electron beam welds in Ti-6Al-4 V

Reduced pressure laser welds were made using a 6-kW commercial fiber-laser system on Ti-6Al-4 V and compared to electron beam welds of the same beam diameters as measured by beam diagnostics. The laser welds showed keyhole characteristics under easily achievable mechanical pumped vacuum levels of 1 mbar pressure that nearly matched the electron beam weld penetrations made at 9 × 10–5 mbar vacuum. Ti-6Al-4 V alloys were used to represent refractory metals such as vanadium, tantalum, zirconium, or molybdenum that require vacuum or highly protective inert gas protection systems to prevent adverse interactions with air and can be difficult to weld under non-vacuum conditions. Results show that laser weld depths of 20 mm with aspect ratios of 17:1 can be made under what appears to be stable keyhole behavior as the result of reduced pressure. The effect of fiber diameter was examined using 0.1-, 0.2-, and 0.3-mm fibers, showing that small spot sizes can easily be achieved at long focal length lenses of 400 and 500 mm. The 0.1- and 0.2-mm fibers produced keyhole welds with minimal amounts of porosity, which was only present at 2 kW or higher, while the 0.3-mm fiber produced keyhole welds with more rounded roots that were porosity free as shown by radiography up to the maximum power of 6 kW. Correlations between weld depth and processing conditions are presented for the reduced pressure laser. These results are directly compared to electron beam welds, facilitating design of future reduced pressure laser systems targeted for deep weld penetrations historically developed for electron beams.

Formability behavior, microstructural evolution, and mechanical properties of GH4169 and electroformed Ni electron beam welded joint

The dissimilar joint between GH4169 and electroformed Ni (E-Ni) was prepared by electron beam welding. The incomplete fusion defect of GH4169 and E-Ni joint was solved by the welding method of electron beam offset to the E-Ni side, and the influence of electron beam offset on the joint formation was mainly studied. The microstructure showed that weld metal was primarily composed of γ phase and Laves phase precipitated between dendrites. The influence of the electron beam offset on the mechanical properties of the joint was emphatically studied. When the electron beam offset was increased from 0 mm to 0.6 mm, the hardness of the fusion zone (FZ) decreased from 240 HV to 160 HV, which was caused by the reduction of the γ″ phase and strengthening elements such as Nb, Mo, and Ti in the FZ. The tensile strength of the upper part of the joint was more than 400 MPa, and the elongation after fracture was more than 15%. However, incomplete fusion defects led to a significant decrease in the tensile strength of the lower part welded joint. When the offset was 0.4 mm and 0.6 mm, the strength of the lower part increased to more than 400 MPa.

Metallurgical processes in the weld metal at electron beam welding of 01570 aluminium alloy

The Paton Welding Journal, 2022, №07. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Interaction of dislocation/compensated precipitates and mechanical property optimization of electron beam welded aluminum-lithium alloy with scandium addition

In view of the precipitate deficiency and mechanical property deterioration, Sc was added into the weld of aluminum-lithium alloy electron beam welded joint to achieve precipitate compensation and the consequent mechanical property optimization. Quantities of intragranular angular Al3Sc precipitated inside the weld after adding Sc, corresponding to the grain refinement effect and dispersoid strengthening effect. The continuous brittle T2 (Al6CuLi3) quasi-crystal at grain boundaries of weld was transformed into intermittent state. The tensile strength of the joint was optimized from 335 MPa (61% of base metal) to 426 MPa (78% of base metal) as Sc was added into the weld, which was mainly due to the dispersoid strengthening effect of Al3Sc and morphology transformation of brittle T2 (Al6CuLi3) quasi-crystal. Dislocation clusters interacted with Al3Sc, indicating a pronounced inhibitory effect on dislocation movement. The novel phenomena of four-chain-shaped dislocations and dislocation loops were found at Al3Sc corners deriving from the attraction to dislocations. The formation model was proposed for the two kinds interaction between Al3Sc/α-Al interface and dislocations.

Microstructures and mechanical properties of AF1410 steel processed by vacuum electron beam welding with multiple beams

Abstract Electron beam welding (EBW) with multiple beams is an advantageous technology to weld parts, as it contributes to decreasing welding distortions and improving mechanical properties. EBW with multiple electron beams was applied to welding simultaneously with auxiliary heating, in a rhombus scanning design, and the energy ratio was 1:1 for AF1410 steel welding. The welds of EBW with multiple beams were nail shaped with a width of 2.54 mm, which were more uniform than those of conventional EBW, and the transversal and longitudinal distortions were lower. The microstructures of specimens processed by EBW with multiple beams contained martensite and a small amount of austenite, and the martensite laths were smaller and more homogeneous than those of conventional EBW. The microhardness values were also more uniform than those of conventional EBW specimens. The tensile strengths of the joints were above 1754 MPa, equivalent to those of conventional EBW, and the percentage elongations were above 9.7 %, which were higher than those of conventional EBW. The microstructure homogeneity and refinement of EBW with multiple beams contributed to improving the mechanical performance.

Swarm Intelligence-based Modeling and Multi-objective Optimization of Welding Defect in Electron Beam Welding

Swarm Intelligence-based Modeling and Multi-objective Optimization of Welding Defect in Electron Beam Welding

Microstructure and properties of vacuum electron beam welded WE43 magnesium alloy joint

This study presents the microstructure and properties of vacuum electron beam welded WE43 magnesium alloy joint. The process parameters of acceleration voltage 150 kV, electron beam current 120 mA and welding speed 35 mm/s are used for vacuum electron beam welding of WE43 rare earth magnesium alloy plate. In this study, the main compositions of the weld are α-Mg and a small amount of eutectic rare earth phase β-Mg24Y5. The mass fraction of the rare earth phase β-Mg24Y5 in the weld area is more than that of the base metal. Segregation of Zr-rich particles can occur in weld zone. The average hardness of the weld is about 27% higher than that of the base metal, and the hardness near the center line of the weld is the highest. The yield strength, tensile strength and elongation of the joint are higher than that of the base metal by approximately 17%, 14% and 41%. Tensile fracture morphology of the welded joint is characterized by ductile and brittle mixed fracture. So, electron beam welding can achieve the connection of WE43 magnesium alloy plate with excellent microstructure and performance. It may be of great significance for this study to expand the application of rare earth magnesium alloy.

Study of micro-porosity in electron beam butt welding

As complete elimination of porosity from the weld is very difficult, the next option available is to minimize this weld porosity, which is crucial for the safe performance of the welded components. However, this investigation through experiments alone is very tedious and time consuming. Additionally, very limited models are available in the literature for accurate prediction of different porosity attributes. The present study, thus, addressees both the experimental as well as modelling aspect on the study of micro-porosity during electron beam welding (EBW) of SS304 plates. Welding parameters are reported to have significant influence on the micro-porosity. Hence, the influences of these parameters on micro-porosity attributes, namely pores number, average diameter, and sphericity are extensively studied experimentally employing optical microscopy (OM), scanning electron microscopy (SEM), X-ray computed tomography (XCT), and Raman spectroscopy. This is followed by an elaborate modelling using seven popular and well-recognized machine learning algorithms (MLAs), namely multi-layer perceptron (MLP), support vector regression (SVR), M5P model trees regression, reduced error pruning tree (REPTree), random forest (RF), instance-based k-nearest neighbor algorithm (IBk), and locally weighted learning (LWL). These different techniques enhance the chance of obtaining the better predictions of the said micro-porosity attributes by overcoming the effect of data-dependence and other limitations of individual MLAs. The different model-predicted micro-porosity data are also validated through experimental data. Statistical tests and Monte-Carlo reliability analysis are additionally utilized to evaluate the performances of the employed algorithms. IBk and MLP are overall found to perform well.

A Mathematical and Experimental Approach to Improve Strength and Corrosion Resistance of Gas Tungsten Arc, Electron Beam and Friction Stir Welded AA2219-T87 Al-Alloy

A Mathematical and Experimental Approach to Improve Strength and Corrosion Resistance of Gas Tungsten Arc, Electron Beam and Friction Stir Welded AA2219-T87 Al-Alloy

Comparison of penetration depth in bead-on-plate welds of thick-walled steel sheets with Laser Beam Welding in Vacuum and Electron Beam Welding

Electron Beam Welding is unchallenged concerning weld seam quality, but in case of penetration depth, the Laser Beam Welding in Vacuum (LaVa) can keep up and even outperform EBW in case of bead-on-plate welds using maximum beam power of 40 kW. The work presented here combines the advantages of reduced working pressure with modern high energy Laser beam sources and extends the recent limits of deep penetration welding to a defect-free single layer weld seam with a penetration depth of 115 mm in medium strength steel S355JR.

Physical Understanding of Active Control of Beam Scanning in Preventing Top Concavity in Electron Beam Welding

Physical Understanding of Active Control of Beam Scanning in Preventing Top Concavity in Electron Beam Welding

Microstructure and Mechanical Characteristics of the First Wall Welded Joints

Vacuum electron beam welding (EBW) is selected as the welding of the water-cooled ceramic breeder (WCCB) blanket. In the process of welding the first wall (FW) of WCCB blanket, it is necessary to add a backing plate to the arc section. At this stage, the thickness of reduced activation ferrite/martensite (RAFM) steels is up to 31 mm. In this article, thick plate RAFM steels after hot isostatic pressing (HIP) are welded by EBW, and then different heat treatments are performed. The results showed that, in the welding condition, hardness of welded joints was changed slightly. The highest hardness of the joint is 440 HV while the lowest is 290 HV, and a softening zone was observed in the heat-affected zone (HAZ). Moreover, after different heat treatments, the welding seam changed into the tempered martensite. In addition, the hardness of base metal and welded joints is all reduced, and the performance of welded joints in quenched and tempered conditions is better than that in normalized and tempered conditions.

Surface Vaporization of High-Strength Aluminum Alloy During Electron-Beam Welding

Surface Vaporization of High-Strength Aluminum Alloy During Electron-Beam Welding

Development of reduced activation ferritic/martensitic steels in China

Reduced-activation ferritic-martensitic (RAFM) steel is considered as the primary candidate structural material for blankets of ITER, CFETR and DEMO. Several RAFMs have been developed in China (CN-RAFMs) such as CLAM, CLF-1, modified RAFMs and oxide dispersion strengthened RAFMs (ODS-RAFMs). The mechanical properties, irradiation behaviors, additive manufacturing and joining technologies of structural materials have been comprehensively studied. Qualifications of CN-RAFMs are on-going for ITER-TBM fabrication, with emphasis on material property databases and standardization. A new neutron irradiation program is being carried out for a series of fusion materials e.g. RAFMs and ODS-RAFMs with doses up to 40 dpa. Joining technologies (e.g. electron beam welding, tungsten inert gas welding, laser beam welding and diffusion welding, etc.) and advanced additive manufacturing are performed to overcome the big challenges of the blanket fabrication before ITER, CFETR and DEMO. The databases and standards for CLAM and CLF-1 were established respectively, and the specification and qualification of them are underway for ITER-TBM.In this paper, the latest development and strategy on fusion energy in China are briefly introduced, and the progresses of R&D activities on CN-RAFMs aiming for the engineering applications are reviewed.

Numerical Evaluation of Temperature Distribution in Copper-Stainless Steel 304 Dissimilar Metals during Electron Beam Welding

Electron beam welding plays an important role in joining dissimilar metals. This paper describes a numerical method to find the temperature distribution in dissimilar metals during Electron Beam Welding. Copper and SS304 are considered as dissimilar metals for this study. When the high beam of electrons hits the metals, heat transfer is accomplished by a phase change due to the heat absorption in the active zone and thus the metals melts. A moving interface exists as a function of time which separates two regions of different properties. Due to the difference in physical properties of both copper and stainless steel the distribution of temperature varies in both the metal. Numerical calculations have been done to find the temperature travelled in both metals when a moving heat source acts on it.

Microstructure and mechanical properties of electron beam welded TiZrNbTa refractory high entropy alloy

It is stringent to develop welding techniques for refractory high entropy alloys (RHEAs) to fabricate large-sized components, since it is difficult to fabricate large-sized RHEA castings because of their poor fluidity and severe element segregation. Here, we first time utilize electron beam welding (EBW) to join TiZrNbTa RHEA, and a defect-free joint is successfully achieved. After EBW, a coarse casting microstructure is largely refined with the reduction of casting porosities. The average hardness in the entire joint is almost uniform, which is the comprehensive effect between the weakening of solution strengthening and the grain refinement strengthening. The tensile strength of the joint achieves 940 MPa, with a high strength efficiency of 90%. This study provides a way to fabricate large-sized RHEA components.