Electron Beam Welding Research Articles

Micromechanical testing and microstructure analysis of as-welded and post-weld heat-treated Ti-6Al-4V alloy

The microstructural evolutions and variations in mechanical performance of electron beam welded (EBW) Ti-6Al-4V (Ti64) alloy have been investigated. The effects of heat treatment on the microstructure of welded samples have been studied after post-welding solution treatment and ageing. The martensitic phase α′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }{\\prime}$$\\end{document} has been confirmed using transmission electron microscopy (TEM). Electron backscatter diffraction (EBSD) has been used to investigate the phase and grain morphology. Results showed that the martensitic α′ phase coarsened, the size of heat-affected zone (HAZ) changed and grains in the base materials (BMs) had grown after the post-weld heat treatments (PWHT). The tensile behaviour of electron beam welded Ti64 has been investigated using in situ tensile testing monitored by optical microscopy. The deformation and failure were directly revealed during the in situ tensile process. Results showed that the EBW Ti64 samples have different failure locations after receiving different post-weld heat treatments. The relationship between the post-weld heat treatments, microstructural evolution and mechanical properties of EBW Ti64 were investigated. Thermodynamic databases were used to predict mechanical properties—including the yield strengths—of the titanium alloy for different grain sizes, representing different post-weld heat treatment operations, and these were embedded into a finite element modelling framework to simulate the tensile testing specimens to understand the mechanical fields experienced such as stresses and strains, just prior to failure.

Specimen reconstitution method for the assessment of fracture properties of reactor pressure vessel steels

Routine testing of the fracture properties of irradiated surveillance specimens is a critical method for evaluating irradiation embrittlement in reactor pressure vessel (RPV) steels. Given the limited space in irradiation surveillance tubes, specimen reconstitution technology is expected to provide a viable solution to the shortage of irradiated specimens. This study investigates the specimen reconstitution method for 16MND5 steel 0.5 T CT specimens used in the RPV. By studying the local mechanical properties of the residual specimen and performing finite element analysis of the crack tip plastic zone, the appropriate size for specimen reconstitution is determined. The electron beam welding method is used to join the residual specimen and the base material, and the J-integral formula for the reconstituted specimen is determined based on the finite element analysis, taking into account the influence of the weld seam and the degradation of the mechanical properties of the residual specimen. The feasibility of the specimen reconstitution method is validated through fracture tests on base material specimens and reconstituted specimens at different temperature.

Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue.This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Study on the Electron Beam Repair Welding of 5000 Aluminum Alloys

Electron beam welding (EBW) has been attracted due to its high energy density, high depth-to-width ratio, low thermal strain, compared with arc and laser welding. In addition, it ensures high quality weld joint in structural metals in a wide range of thickness from 0.025 mm to 300 mm. Therefore, EBW is widely used in industries such as automotive, aviation, nuclear power plant, etc. Although a lot of studies on EBW for several decades have been presented, EB based repair welding with supplement of filler metal has less reported. In this work, EB repair welding for 5083 aluminum alloys was investigated because the aluminum alloys are becoming more important as a lightweight material in mobility industries. Material characterization and mechanical properties of the repair-welded specimens were evaluated, compared with characteristics of base metal and bead welding without repair. The optimized experimental conditions showed tensile strength of 294 MPa, which is a similar to base metal. Our study indicates that EB repair welding can be considered for the candidate of repair welding of aluminum alloys.

A Review of Welding Process for UNS S32750 Super Duplex Stainless Steel

Super duplex stainless steel UNS S32750 is widely used in marine industries, pulp and paper industries, and the offshore oil and gas industry. Welding manufacturing is one of the main manufacturing processes to make material into products in the above fields. It is of great importance to obtain high-quality welded UNS S32750 joints. The austenite content and ferrite content in UNS S32750 play an important role in determining UNS S32750 properties such as mechanical properties and corrosion resistance. However, the phase proportion between the ferrite phase and austenite phase in the welded joint will be changed during welding. Lots of research has been done on how to weld UNS S32750 and how to obtain welded joints with good quality. In this work, the recent studies on welding UNS S32750 are categorized based on the welding process. The welding process for UNS S32750 will be classified as gas tungsten arc welding, submerged arc welding, plasma arc welding, laser beam welding, electron beam welding, friction stir welding, and laser-MIG hybrid welding, and each will be reviewed in turn. The microstructure and properties of the joints welded using different welding processes will also be discussed. The critical challenge of balancing the two phases of austenite and ferrite in UNS S32750 welded joints will be discussed. This review about the welding process for UNS S32750 will provide people in the welding field with some advice on welding UNS S32750 super duplex stainless steel.

Effect of Beam Oscillation on Weld Formation, Porosity, Grain Structure, and Mechanical Properties in Electron Beam Welding 5B70 Aluminum Alloy

Effect of Beam Oscillation on Weld Formation, Porosity, Grain Structure, and Mechanical Properties in Electron Beam Welding 5B70 Aluminum Alloy

Use of a structure-borne sound-based in-process sensor system to identify Weld seam irregularities during electron beam welding

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.

Electron beam welding residual height measurement by line laser illumination and telecentric imaging

Residual height significantly affects the fatigue life of electron beam welding (EBW) joints. Therefore, accurate measurement of the EBW residual height is necessary for grinding and removing it, to improve the fatigue resistance of the joint. However, there is no specific method for the EBW residual height measurement, and existing methods for other regular welds are often unsuitable due to their limitations. This paper proposes a novel EBW residual height measurement method, to the best of our knowledge, based on line laser illumination and telecentric imaging [line laser telecentric imaging (LLTI)]. Unlike regular line-structured light methods based on near-centered imaging, telecentric imaging has advantages on the simple imaging model, minimal aberration, and can avoid a complex calibration process and improve the detection accuracy. In this paper, residual height calculation algorithms for both flat and cylindrical bases of LLTI are discussed, and, for cylindrical base welds, an error analysis is conducted and a corresponding solution is proposed. A series of experiments is conducted, and the accuracy is under 0.02 mm, which proves the effectiveness of the LLTI method.

Effect of Beam Offset of Microstructure and Mechanical Properties of Electron Beam Welding of TZM to Ti-6Al-4V Alloy

Effect of Beam Offset of Microstructure and Mechanical Properties of Electron Beam Welding of TZM to Ti-6Al-4V Alloy

Thermal stability of electron beam welded AlCoCrFeNi2.1 alloy

Abstract AlCoCrFeNi2.1 alloy, which belongs to the group of eutectic high-entropy alloys (EHEAs), possesses a combination of increased strength and ductility. It should retain these properties over a wide temperature range due to the high entropy effect of the system. At the same time, eutectic alloys are generally considered to have good castability, which increases the possibility of casting the alloy in larger volumes. One of the processes, that the alloy does not avoid when applied in industry, are the various joining techniques including electron beam welding. The weld area is often in a non-equilibrium state, which increases the risk of failure during operation. The paper therefore discusses the stability of the microstructure and mechanical properties of AlCoCrFeNi2.1 alloy when exposed to short-term elevated temperatures. The material heated at 900 °C for 1 h in a vacuum furnace was observed using light and electron microscopy, analyzed for chemical and phase composition and finally subjected to HV0.1 hardness measurement and tensile strength test. The resulting condition was compared with the welded joint before exposure to elevated temperature. The microstructure of the weld was formed by a fine lamellar eutectic over the entire observed area. EBSD analysis confirmed the presence of a combination of FCC and BCC phases. The material hardness reached an average value of 370 HV0.1. Maximum tensile strength of the weld joint was measured at 944 MPa with the corresponding displacement of the crosshead 6.1 mm. The welded joint demonstrated sufficient stability and the ability to withstand short-term severe elevated temperature conditions.

Influence of heat treatment on the structure and mechanical properties of pseudo α-titanium alloy in a welded joint

The object of this study was the weld material of a new Ti-6.1Al-6.0Zr-6.3Sn-3.2Mo-1.1Nb-1.2Si 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

Microstructure and Mechanical Properties of GH3535 Superalloy Joints Using Electron Beam Welding

To achieve low‐stress and small‐deformation welding of thin‐walled structures for the fourth‐generation nuclear power plants, GH3535 superalloy is welded to itself using electron beam welding (EBW). The microstructure and mechanical properties of the GH3535 superalloy joints are characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), hardness, and tensile tests. A macro‐defect‐free GH3535 superalloy joint could be obtained using 22 mA welding beam current under 65 kV welding voltage with 300 mm min−1 welding speed. Different sub‐grain solidification morphologies are observed at the weld zone because of the influence of composition undercooling on the solidification process of the weld pool. The M6C type carbides formed in the weld zone and heat‐affected zone (HAZ) take place eutectic transformation under the action of thermal cycles. The eutectic transformation of M6C has no significant effect on the strength of HAZ, whereas this phenomenon is beneficial to hinder the dislocation movement in the weld zone, thereby promoting the tensile strength of the joint. The Vickers hardness of weld zone and HAZ are 250.6 and 252 HV0.5, remarkably lower than that of the base metal (261.2 HV0.5), due to the grain coarsening in those zones. The tensile strength of the GH3535 superalloy joint reached 791 MPa, ≈93.5% that of the base metal, with the fracture occurred in the weld zone.

Electron beam welding of the novel L12 nanoparticles-strengthened medium-entropy alloy Ni41.4Co23.3Cr23.3Al3Ti3V6: Microstructures, mechanical properties, and fracture

Although low levels of vanadium-doping can enhance the friction stress and strength of L12-nanoparticles strengthened medium-entropy alloys (MEA), how high concentrations of vanadium affect the weldability, microstructure, mechanical properties, and fracture behavior remains unknown. In this work, we designed a vanadium-doped, L12-nanoparticle-strengthened MEA Ni41.4Co23.3Cr23.3Al3Ti3V6 (at.%), which showed a high fracture toughness of 238 MPa × m1/2, a high friction stress of 410 MPa, and a Hall-Petch strengthening coefficient of 782 MPa × μm1/2. Pieces of the HEA were joined using electron-beam welding (EBW). Strong yet ductile defect-free joints were produced which had coarse columnar grains (88 μm) with a {110}<001> texture in the fusion zone, which was larger than the equiaxed grains in the heat-affected zones (14.9 μm) which had strong {110}<001> and relatively weak {110}<112> texture. In contrast, the base materials had fine grains (2.2 μm) with a strong {110}<111> and a relatively weak {110}<112> texture. The EBWed MEA showed a high yield strength of 599 MPa, a high ultimate tensile strength of 939 MPa, a good fracture strain of 20 %, and a fracture toughness of 198 MPa × m1/2, which were 75 %, 83 %, 58 %, and 83 %, respectively, of the values of for the thermo-mechanically treated counterpart. The reduced strength arose from the coarse columnar grains, while the reduced fracture strain and fracture toughness could be ascribed to the reduced deformation twinning and the absence of annealing twins, which produced a poor strain hardening capability. The EBWed MEA exhibited abundant dislocation networks, indicating that a high concentration of vanadium inhibited the occurrence of stacking faults and nanoscale deformation twins.

Electron Beam Welding of Copper and Aluminum Alloy with Magnetron Sputtered Titanium Filler

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.

Compressive behavior and deformation mechanisms of gradient microstructures in a dissimilar welded joint

In this study TC4/TC17 titanium alloy dissimilar joints were obtained via vacuum electron beam welding. The compressive behavior of base metals and joint at different strain levels was studied, along with microstructural and fracture surface observations. The true stress–strain curves of base metals and joint at different strains demonstrated smooth and continuous plastic deformation characteristics. The compressive yield strength of the joint (1065 MPa) was basically equivalent to that of TC17 alloy (1196 MPa), which was significantly higher than that of TC4 alloy (920 MPa) for the failed samples. However, the compressive fracture strain of the joint was lower than that of base metals. Comparison of the microstructures of base metals and joint deformed at different strains, it revealed that the equiaxed α phase in TC4 alloy mainly underwent the deformation, while the TC17 alloy mainly relied on the rotation of lamellar grains to resist the deformation. In the dissimilar joint with a large microstructural gradient, the compressive deformation of several zones, including the weld zone, far heat-affected zone and the base metal, was also related to the rotation of finer grains.

Determination of Cast-Metal Structures and Welded Joints After Electron-Beam Welding of the Intermetallic Titanium Alloys Ti−28Al−7Nb−2Mo−2Cr Obtained by Electron-Beam Melting Method

Determination of Cast-Metal Structures and Welded Joints After Electron-Beam Welding of the Intermetallic Titanium Alloys Ti−28Al−7Nb−2Mo−2Cr Obtained by Electron-Beam Melting Method

Microstructure and mechanical properties in electron beam scanning welded joints of super thick titanium alloy plates

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.

Study on the effect of Sc and Zr addition on microstructure, mechanical property and fracture behavior of electron beam welded Be-Al alloys

Because of various excellent properties of low density, high specific strength and stiffness, high modulus, good thermal stability and corrosion-resistant, beryllium-aluminum (Be-Al) alloys have shown great potential to be used in nuclear industries. However, Be-Al alloys suffer from the bottlenecks of low solubility between Be and Al and the lack of effective technology for fabricating large-sized products. Herein, based on Sc and Zr addition, Be-Al-Sc-Zr alloys are successfully fabricated by conducting the electron beam welding (EBW) technology, and the effect of Sc and Zr addition on microstructure, mechanical property and fracture behavior of Be-Al-Sc-Zr alloys are studied. Microstructural characterizations show that both the EBWed Be-Al and Be-Al-Sc-Zr alloys exhibit two distinct zones of substrate zone (SZ) and fusion zone (FZ). Compared to grain size of the SZ and FZ in Be-Al alloys, grain sizes of these two zones in Be-Al-Sc-Zr alloys are significantly refined, thus leading to ultimate tensile strength (UTS) of the Be-Al-Sc-Zr alloys (∼176 MPa) approximately 150 % higher than that of the Be-Al alloys (∼118 MPa). Besides, a newly generated third phase (TP), which is confirmed as Be13(Scx, Zr1-x), forms within Al phase in both SZ and FZ of the Be-Al-Sc-Zr alloys. Different from fracture behavior of Be-Al alloys that preferentially fractures within Al phase or near the Be/Al interface, fracture of the Be-Al-Sc-Zr alloys is prone to occur within Be phase. As revealed by the calculation results of finite element method (FEM), the underlying mechanism for different fracture behaviors mainly ascribe to that the reinforcement of Al phase and existence of the newly formed TP can greatly increase the internal stress and even causes stress concentration within Be phase of the Be-Al-Sc-Zr alloys. The present findings may provide more insights to the micro-alloying and deformation mechanism of Be-Al alloys that with enhanced mechanical properties.

Investigation on the room temperature compressive creep behavior of TC4 titanium alloy joints with vacuum electron beam welding

The room temperature compressive creep behavior is a key issue for the titanium alloys welded structural components served in deep-sea environment. In the present work, the compressive creep behavior of different areas for TC4 titanium alloy joints with vacuum electron beam welding was systematically studied, and it is found that the fusion zone (FZ) of TC4 titanium alloy joints has the minimum creep strain rate. This is mainly because the creep deformation of TC4 titanium alloy is mainly controlled by the movement of dislocations in the α or α′ phases, the size of α′ phase in FZ is small, and thus the dislocation slip is limited. MD simulation results have further revealed that the room temperature compressive creep nature of α-Ti can be regarded as a dynamic hysteresis phenomenon in plastic strain and is dominated by the dislocation movement.

Numerical simulation and properties analysis of Ta10W alloy joints prepared by electron beam welding

Vacuum electron beam welding has the characteristics of concentrated energy, controllable heat input, almost no pollution, and a small heat-affected zone. In this study, the Ta10W alloy was successfully connected by electron beam welding (EBW), and numerical simulations were employed to examine the distribution of temperature and stress fields throughout the welding process. Additionally, the influence of EBW on the microstructure and corrosion resistance of the welded joints was scrutinized. Findings indicate that the welding heat process led to a reduction in grain boundary energy, thereby facilitating thermal activation processes that contributed to grain growth. Grain boundary migration and possible dynamic crystallization led to the appearance of the coarse columnar crystal structure in the welded joint. A three-dimensional, nonlinear, transient, thermo-mechanically coupled finite element model was developed for the electron beam welding of Ta10W alloy. The shape characteristics and size of the weld and transient thermal cycles calculated by numerical simulations were in reasonable agreement with experimental results. Electron beam welding reduced the corrosion resistance of the Ta10W alloy, and the corrosion product was mainly composed of Ta, O and Na.