Oscillations Of Electron Beam Research Articles

Achieving high precipitation phase proportion and mechanical properties of vacuum electron beam oscillation welded joints of near β titanium alloy thick plates by the interlayer addition

The strengths of near β titanium alloy thick plate joints are usually reduced after fusion welding since only a small amount of α phase precipitates during cooling. In this study, vacuum electron beam welding (VEBW) with a 1-mm-thick Ti-6Al-4V (Ti-64) interlayer using novel sawtooth scanning (SS) pattern was designed to regulate the morphology and proportion of α phase in 30-mm-thick near β titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe, which largely enhanced the joint properties. The SS-joint with Ti-64 interlayer enhanced the joint strength most, with the increase in the tensile strength from 849 MPa for the joint without interlayer addition to 991 MPa for the SS-joint, which could usually reach similar strengths to the annealing treatment joints as reported. The improved strength was mainly attributed to largely increased proportion of acicular α phase for the SS-FZ with Ti-64 interlayer. The fracture location of the SS-joint with Ti-64 interlayer was in the heat affected zone (HAZ). Furthermore, the impact energy of HAZ in SS-joint was slightly higher than that of HAZ without interlayer addition, even superior to that of base material. This study provides a new economy and high efficiency welding method to improve the mechanical properties of near β titanium alloy thick plates.

Effect of Electron Beam Oscillation on Evolution of Microstructure in Ti6Al4V Alloy Weldments

Electron Beam Oscillation refers to the movement of the electron beam during welding or other processes. This movement can affect the heat input and distribution, which in turn can impact the microstructure and properties of the material being processed. Ti6Al4V is a common titanium alloy that is known for its high strength, corrosion resistance and biocompatibility. Understanding how electron beam oscillation affects the properties of this alloy having important implications for its use in various applications. The study likely involves conducting experiments where Ti6Al4V samples are subjected to different levels of electron beam oscillation and then analyzing their microstructure, micro hardness, and tensile strength. The results of the study can help to provide insights into the optimal conditions for processing Ti6Al4V using electron beam oscillation and also contribute to our overall understanding of the behavior of this alloy. Keywords: Component, formatting, style, styling

Upper-hybrid oscillations of high current relativistic electron beam under conditions of magnetic self-insulation

Upper-hybrid oscillations of high current relativistic electron beam under conditions of magnetic self-insulation

Investigation of the effects of beam oscillations in electron beam–welded S1100M TMCP steel

The development of thermomechanically controlled processed (TMCP) high-strength steel (HSS) has significantly contributed to designing and developing the intricate structural components. It has broader applications in the cranes and lifting process industry (base frame, crane jibs, and crane columns), trailers, agricultural and forestry machinery, earth-moving equipment, etc. However, the development of new-grade steels with higher tensile strength led to higher requirements for welded joints, and the associated weldability issues have inspired detailed studies on electron beam welding (EBW) with different beam oscillations. Beam oscillation application with EBW processes improves the welding efficiency, weld quality, weld geometry, keyhole, etc., affecting the welded joints mechanical and microstructural properties. Thus, the present study investigates the impact and comparison of various beam oscillations on the microstructural and mechanical properties of EB-welded S1100M steel. The influence of welding parameters on the microstructure of welded joints was analyzed using a scanning electron microscope (SEM) and electron backscattered diffraction (EBSD). The analysis focused on evaluation of grain sizes, morphologies, distributions, and crystallographic orientations of different phase constituents in fusion zone (FZ) and heat-affected zone (HAZ). The mechanical properties were analyzed using hardness, tensile, and Charpy V-notch impact tests. The texture in the FZ is typically random, while the HAZ typically exhibits a strong rolling texture. In general, the cooling rate in EBW is very fast, possibly resulting in a fine-grained structure and reduced formation of coarse second-phase particles in the weld zone. The elliptical beam oscillation showed the highest hardness in HAZ 450 HV10. Elliptical beam oscillation slightly improves the welded joint’s tensile strength, and the impact test showed mixed fracture behavior.

Unveiling Impact of Electron Beam Optics on Weld Attributes in EN30B Steel

The influence of electron optics in terms of beam oscillation (BO) has been studied on weld quality of several steels and reported to develop cosmetic weld with smooth surface and enhanced weld properties. However, effect of electron beam oscillation on the weld quality of medium carbon low alloy steel, especially EN30B, have not reported well and investigated in this study. By manipulating magnetic lens in-line with electron beam, the diameter of oscillating beam (OD) and its effect on weld quality has been studied. The OD was changed between 0.5 mm and 2 mm. Numerous tests, including XRD, SEM, EBSD, hardness, wear, and tensile, were used to characterize the weld quality. Welds with BO significantly lowered the heat input rate than welds without oscillation. In presence of beam oscillation, retained austenite (RA) in the weld increased and it became least in welds made without BO. Tensile residual stress was found in the fusion zone (FZ) and it was higher with beam oscillation, especially with higher OD. In contrast to columnar grains predominantly found in welds made without BO, significant equiaxed grains were identified in welds made with BO. Nonmetallic inclusions (NMIs) in the weld became finer and less by use of BO. Introducing BO enhanced the hardness and reduced wear rate of weld, particularly at greater beam OD. Although Weld strength was diminished in comparison to the base metal (BM), beam oscillation increased the weld's ductility and strength.

Effect of Electron Beam Oscillation Welding of Molybdenum and Titanium

Electron beam welding of pure molybdenum (Mo) and titanium alloy (Ti-6Al-4V) was performed with beam oscillation. The effects of beam oscillation with offset on the welded joints were analyzed in terms of microstructure, element distribution, chemical composition, microhardness, and tensile strength. The results showed that the fusion zone expanded with beam oscillation. Reaction layers were generated in both joints welded with and without beam oscillation. The thickness of the reaction layers decreased along the perpendicular direction. The reaction layers were (Mo, Ti) solid solutions. Both welded joints consisted of single-phase Mo, the β-Ti phase, and Mo-Ti solid solutions. The microhardness distribution of the joint welded with beam oscillation was more consistent than that of the joint welded without beam oscillation, and the maximum hardness was reduced from 340 HV to 270 HV. The tensile strength increased from 124 MPa to 204 MPa.

Microwave generation from betatron oscillation of slow electron beam in DC cross-fields configuration

A high-efficiency mechanism of microwave (MW) generation from slow electron beam (e-beam) is investigated in details. Space-inhomogeneous density profile of the e-beam enables its current vortex profile ∇ × j easy to be modified significantly by external fields. Suitable DC cross-fields configuration can modify time behavior of the ∇ × j of an e-beam from monotonically-varying to oscillatory. Under available not-too-severe values of beam peak density and beam drifting velocity, such a time-oscillatory current vortex can be tuned to have a narrow-spectrum around a desired central frequency within a broad range from MHz to Thz. The mechanism is applicable to slow non-relativistic e-beam and hence does not need bulky cooling component and high-voltage component. This favors the whole vacuum electron devices (VEDs) to be compact enough without at the cost of lower output power.

The effect of electron beam oscillation on the porosity of third-generation AW2099 aluminium lithium alloy welded joints

The influence of beam oscillation on the porosity of third-generation aluminium lithium (Al-Li) alloy was evaluated. 4 mm thick AW2099 was used for electron beam welding. Heat inputs of 55 J/mm and 66 J/mm with and without beam oscillation were used for the production of butt-welded joints. Circular oscillation pattern was used for welding. The higher the heat input, the larger the porosity. Furthermore, porosity of welded joints produced with a heat input of 55 J/mm dropped from 0.23 to 0.19 % when beam oscillation was utilized. Similarly, the application of electron beam oscillation for the production of welded joints with a higher heat input of 66 J/mm led to the drop of porosity from 0.33 to 0.2 %.

Electromagnetic design of the transition section between modules of a wakefield accelerator

The electromagnetic design of a transition section consisting of couplers for extracting the 180-GHz ${\mathrm{TM}}_{01}$ accelerating mode and 190-GHz ${\mathrm{HE}}_{11}$ dipole mode of a cylindrical corrugated waveguide used as a collinear wakefield accelerator is presented. Extraction of the high power accelerating mode reduces the power dissipation in the corrugated accelerating structure and allows the much weaker ${\mathrm{HE}}_{11}$ mode to be isolated and used to monitor the stability of the 10-nC electron drive bunch. The final design demonstrates wide bandwidth and high coupling efficiency of two couplers. The design was also optimized to have the surface electric and magnetic fields that do not exceed those in the corrugated waveguide. Finally, coupling between the drive electron bunch and the ${\mathrm{HE}}_{11}$ dipole mode in the corrugated waveguide is considered and the utility of the ${\mathrm{TE}}_{11}$ coupler for detecting the electron beam oscillations in the wakefield accelerator is demonstrated using a few representative examples of oscillations below and above a threshold of the beam breakup instability.

Radial oscillation of intense relativistic electron beam in low-magnetic-field foil-less diode

The radial oscillation of an intense relativistic electron beam possesses two main features of the spatial period and the radial oscillation amplitude in a low-magnetic-field foil-less diode, and the large radial oscillation extremely limits the beam–wave conversion efficiency and stability of a high-power microwave device. Thus, the formation mechanism of the radial oscillation is analyzed in detail. The results show that the radial oscillation of an electron beam consists of a great number of electrons with different Larmor radii and guiding centers, and the large radial oscillation is mainly caused by the strong radial electric field and the directional difference between the electric field and the magnetic field in the anode–cathode gap. A low diode voltage or a proper large anode radius is beneficial to improve the beam quality. Considering that cathode plasmas have a dominant effect on the spatial distribution of electrons, the explosive emission model was improved with cathode plasmas, and the consistency between simulation and experimental results becomes better.

Effect of non-uniform magnetic field on radial oscillation of electron beam in a low-magnetic-field foilless diode

A theory regarding a non-uniform magnetic field with a parallel gradient is presented. The research results show that a proper non-uniform magnetic field can greatly reduce the transverse momentum of an electron beam and even eliminate its gyration motion, and it depends on the gradient of the magnetic field and the phases of electrons entering and leaving the local magnetic field region. Thus, a magnetic field that decreases along the axial direction is proposed to suppress the radial oscillation of the electron beam. However, in the drift tube, the suppression of the radial oscillation is not obvious, because the large phase differences among electrons lead to a mismatch between the electron beam and the non-uniform magnetic field. Further studies found that the non-uniform magnetic field applied in the anode-cathode gap can not only reduce the phase differences among electrons, but also effectively transform the transverse momentum of the electron beam into its axial momentum. The results obtained by PIC simulations and experiments consistently confirm that the non-uniform magnetic field can significantly suppress the radial oscillation of the electron beam in a low-magnetic-field foilless diode.

Mathematical Model for Metal Transfer Study in Additive Manufacturing with Electron Beam Oscillation

A computer model has been developed to investigate the processes of heat and mass transfer under the influence of concentrated energy sources on materials with specified thermophysical characteristics, including temperature-dependent ones. The model is based on the application of the volume of fluid (VOF) method and finite-difference approximation of the Navier–Stokes differential equations formulated for a viscous incompressible medium. The “predictor-corrector” method has been used for the coordinated determination of the pressure field which corresponds to the continuity condition and the velocity field. The modeling technique of the free liquid surface and boundary conditions has been described. The method of calculating surface tension forces and vapor recoil pressure has been presented. The algorithm structure is given, the individual modules of which are currently implemented in the Microsoft Visual Studio environment. The model can be applied for studying the metal transfer during the deposition processes, including the processes with electron beam spatial oscillation. The model was validated by comparing the results of computational experiments and images obtained by a high-speed camera.

Investigation of the characteristics of ion saturation current in plasma over the keyhole in the process of electron beam welding

The energy spectra of the ion saturation current of the Langmuir probe in the plasma formed over the keyhole directly during the process of electron-beam welding of steel 09G2S with the varied parameters (e.g., the welding speed and focus coil current) has been investigated. The presence of typical zones with the energy spectrum peaks in the low-frequency and high- frequency bands has been shown. It has been established that the peak location in the high- frequency range of the energy spectrum does not depend on the welding modes and the position of the probes relative to the keyhole. The low-frequency range of the energy spectrum depends on the vapor flow density of the keyhole and is rather sensitive to the welding modes. The use of electron beam oscillation makes it possible to control plasma flows and hydrodynamic processes in the penetration channel.

Influence of the beam oscillation parameters on the porosity of electron beam freeform fabricated titanium alloy SPT-2

The effect of electron beam oscillation on the formation of metal during electron beam freeform fabrication has received practically no attention. Nevertheless, it is a variable technological tool that allows to significantly influence the formation of metal during EBFFF process, including the probability of defects formation. The effect of the focus current, the form, and the frequency of the beam oscillation on the formation of pores in single beads by method of electron beam freeform fabrication of the titanium alloy SPT-2 on the substrate of the alloy VT6 was investigated. The porosity of the obtained beads was studied using x-ray images. It was found that too deep an arrangement of the focal plane relative to the substrate surface leads to excessive pore formation. Reducing the oscillation frequency from 1000 Hz to 100 Hz made it possible to completely get rid of the pores in the metal. The use of a spiral-shaped oscillation made it possible to reduce the probability of pore formation in comparison with an oscillation in the form of concentric circles.

Solidification behavior and microstructure of Ti-(37−52) at% Al alloys synthesized in situ via dual-wire electron beam freeform fabrication

Titanium-aluminide (TiAl) alloys are very promising substitutes for Ni-based superalloys, and additive manufacturing, which is a disruptive technology, is a promising way to fabricate them. Ti-(37−52) at% Al walls were successfully synthesized in situ using dual-wire electron beam freeform fabrication (EBF3), and the solidification behavior was characterized according to their chemical composition, phase identification, microstructure and orientation. The Ti-37 at% Al wall was composed of α2 grains with an average size of 100 µm and a random orientation distribution, indicating that the primary phase was the β phase and that the solid-state β→α transformation occurred. The orientation relationships, namely (0001)α//{111}γ and <112¯0>α//<11¯0]γ, were found in the lamellar structure of the Ti-42 at% Al walls, and the α2 phase and γ grains presented < 0001 > and < 111 > orientations in the deposition direction, respectively. This suggests that the formation of a lamellar structure was the result of the solid-state α → α2 + γ transformation, where the α phase was the primary phase. The solid-state α →γ lamellae and α →γ massive transformations in the Ti-49 at% Al wall caused the massive γ phases to have a random orientation and the lamellar γ phases to be oriented along the < 012 > and < 010 > directions in the building direction. The γ dendritic structure, a characteristic solidification structure, indicated that the solidification path of the Ti-52 at% Al wall was L→γ. Solidification during the EBF3 process deviated from the thermodynamic equilibrium state, and the metastable phase formed in the liquid phase as the primary phase. The solidification conditions, including the thermodynamic and kinetic conditions and cooling rate, were analyzed. The results indicate that the primary phases were selected by undercooling, and the microstructure of Ti-xAl (x = the actual Al content in at%) alloys during the EBF3 process was determined to correspond to an estimated undercooling temperature of 240–247 K. However, the cooling rate during solidification was 214.36 K/s, which was not enough to produce such a high undercooling temperature. The high undercooling temperature was the result of melt superheating and electron beam oscillation. A novel solidification process with a low cooling rate and a high undercooling temperature occurred during EBF3.

Influence of electron beam oscillation patterns on the microstructure, texture, residual stress and mechanical properties of Ti-5Al-2.5Sn alloy weldments

Vacuum electron beam welding is widely employed for the welding of titanium alloys using different beam oscillation patterns. Since these patterns influence the physical phenomenon in the weld pool, its effect on the microstructure, texture, mechanical properties and residual stresses is of prime interest. In order to understand this influence, electron beam welding was used to prepare Ti-5Al-2.5Sn weldments using beam oscillations of triangular and rectangular waveform. It was observed that a change of welding pattern had a strong influence on the residual stresses, impact properties and texture of weld zone while tensile properties were not significantly affected. A partial martensitic transformation was observed in both the triangular and rectangular waveform of oscillations. An increase in alpha lathe width was observed in the fusion zone and similar strength of the rectangular pattern as compared to triangular pattern. Despite of this, the observed higher Vickers hardness of the fusion zone of rectangular pattern as compared to triangular and no-oscillation was attributed to texture strengthening using rectangular waveform.

Application of Dynamic Beam Positioning for Creating Specified Structures and Properties of Welded Joints in Electron-Beam Welding.

The application of electron beam sweep makes it possible to carry out multifocal and multi-beam welding, as well as combine the welding process with local heating or subsequent heat treatment, which is important when preparing products from thermally-hardened materials. This paper presents a method of electron beam welding (EBW) with dynamic beam positioning and its experimental-calculation results regarding the formation of structures and properties of heat-resistant steel welded joints (grade of steel 20Cr3MoWV). The application of electron beam oscillations in welding makes it possible to change the shape and dimensions of welding pool. It also affects the crystallization and formation of a primary structure. It has been established that EBW with dynamic beam positioning increases the weld metal residence time and the thermal effect zone above the critical A3 point, increases cooling time and considerably reduces instantaneous cooling rates as compared to welding without beam sweep. Also, the difference between cooling rates in the depth of a welded joint considerably reduces the degree of structural non-uniformity. A bainitic–martensitic structure is formed in the weld metal and the thermal effect zone throughout the whole depth of fusion. As a result of this structure, the level of mechanical properties of a welded joint produced from EBW with dynamic electron beam positioning approaches that of parent metal to a greater extent than in the case of welding by a static beam. As a consequence, welding of heat-resistant steels reduces the degree of non-uniformity of mechanical properties in the depth of welded joints, as well as decreases the level of hardening of a welded joint in relation to parent metal.

Effect of Local Electric Field on Radial Oscillation of Electron Beam in Low-Magnetic-Field Foilless Diode

The effect of the local electric field on the radial oscillation of the electron beam in the low-magnetic-field foilless diode is studied theoretically and experimentally. The results obtained with different methods show good coherence. The radial oscillation amplitude of the electron beam affected by the local electric field depends on the electric field intensity and the phases of electrons entering and leaving the local electric field region. It is found that the enhanced radial electric field near the drift tube head results in the change of the radial oscillation amplitude with the anode–cathode gap. Meanwhile, a method to effectively suppress the radial oscillation is proposed. Optimizing the anode–cathode gap and the tilt angle of the drift tube head can effectively adjust the matching state of the electron phase and the local electric field, and thus the transverse momentum of the electron beam can be greatly reduced due to the negative effect of the radial electric field.

Effect of beam deviation on electron beam welded Ti-22Al-25Nb/TC4 dissimilar alloys

Dissimilar alloys of Ti-22Al-25Nb (at%) and TC4 are welded by electron beam welding (EBW), and the effect of different welding procedures (with electron beam deviation to TC4 side or without) on microstructure and mechanical properties of welded joints are investigated. Results show that the microstructure of fusion zone (FZ) consists of B2 phase and martensitic α′ phase. The heat-affected zone (HAZ) of Ti-22Al-25Nb side near FZ consists of B2 phase and a little of α2 phase, and that of TC4 side near FZ is the α′ phase. When the electron beam is deviated to TC4 side 0.15 mm during welding, the welded joint with good appearance of weld can be obtained, and the ultimate tensile strength and elongation of welded joint reach 967.6 MPa and 3.1%, respectively. The variation of microhardness in weld zone with beam deviation is smaller that of without beam deviation. Electron beam oscillation can stir fully the molten pool during welding, and the main alloying elements distribute uniformly in FZ. On the whole, the mechanical performance of welded joint with beam deviation is better than that of without beam deviation.

Development of electron-beam welding method with inserts

The paper is devoted to the study of welded joints formation process both from homogeneous and dissimilar materials. The investigated welded joints were made by an electron beam using intermediate inserts of small thickness in a narrow gap. The influence of insert size as well as gap size on the stability of weld formation is shown. Electron beam oscillation configurations which eliminate incomplete penetration in weld root are determined. Values of thermal efficiency are experimentally found for different welding speeds. The results of structure study for dissimilar welded joints of plates from carbon steel 20 and austenitic corrosion-resistant AISI 316L steel are presented. The values of penetration rate for base and filler metal are calculated and experimentally confirmed.