Effect of beam current on the microstructure, crystallographic texture and mechanical properties of electron beam welded high purity niobium

Das, Kalyan; Ghosh, Abhishek; Bhattacharya, Anirban; Lanjewar, Harishchandra; Majumdar, Jyotsna Dutta; Ghosh, Manojit

doi:10.1016/j.matchar.2021.111318

Cited by 15 publications

(7 citation statements)

References 47 publications

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“…For the FZ of the IEBW joint, it has to be taken with caution that the intensity of the {001}<100> texture is much higher than that in the base metal and the HAZ. For the {001}<100>, {001}<110>, and {001}<120> textures, the plastic strain ratio (R-value) is not high compared with other textures according to the previous research [ 17 , 40 ]. In addition, the R values in the 0° and 90° directions differ greatly from that in the 45° direction for {001}<100> and {001}<110> textures, which is unfavorable for preventing unstable deformation in the welds of SEBW and IEBW joints.…”

Section: Resultsmentioning

confidence: 87%

“…The microhardness profiles for different oscillating patterns are plotted in Figure 10 . Unlike welding power [ 17 ], oscillating pattern has little effect on the hardness distribution of the welded joints for niobium sheets due to the same heat input and no phase transition for all the joints [ 25 ]. The average microhardness values for the FZ of NEBW, SEBW, CEBW, and IEBW joints are 87.4, 85.6, 87.6, and 86.7, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…What is more, grain structure and crystallographic texture are associated with mechanical properties [ 12 , 13 , 14 ]. According to the previous study [ 15 , 16 , 17 ], the grain structure and texture of the fusion zone and the heat-affected zone in the niobium joints after EBW may have a difference with the base metal due to different thermal processes in these regions, so the microstructure for niobium joints needs further investigation. However, in the previous research [ 18 , 19 , 20 , 21 ], the effect of weld defects and impurities on the superconducting properties of niobium welds has attracted more attention.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness

Tao

Liu

et al. 2022

Materials

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The electron beam welding of the tubes and the half-cells for our 1.3 GHz single-cell superconducting radiofrequency (SRF) cavities is complex due to the different thicknesses of the tubes and the half-cells in the iris region. However, the mechanical properties and microstructure of the iris welds in niobium SRF cavities have barely been explored in previous studies. For high-quality iris welds, welding experiments of niobium sheets of 2 mm and 2.8 mm were carried out under different oscillating conditions. The results show that welding with no oscillation or sinusoidal oscillation may not be applied in actual welding owing to the large misalignment of the bottom surface. The weld grains were not significantly refined through beam oscillation. The joints with infinity oscillation had a higher elongation than circular oscillation, which exhibited a brittle fracture in the tensile tests at 77 K. Nevertheless, the texture of the weld with infinity oscillation implies poor formability, so the feasibility of infinity oscillation in actual welding needs verification in future study.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness

Tao

Liu

et al. 2022

Materials

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“…Therefore, inert gas shielding or a high vacuum is needed during welding. [ 17 ] There have been different studies regarding the electron beam welding (EBW) of pure Nb. Potukuchi et al [ 18 ] studied the superconducting properties of pure Nb and concluded that properties do not degrade due to the EBW.…”

Section: Related Workmentioning

confidence: 99%

Investigations of Microstructure and Mechanical Properties in Wire + Arc Additively Manufactured Niobium–Zirconium Alloy

et al. 2023

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Herein, the feasibility of the gas tungsten arc welding‐based wire + arc additive manufacturing process for fabricating thin wall structures of niobium‐1 wt% zirconium (NbZr1) alloy is investigated. Three different heat input conditions (low, medium, and high) have been selected for fabricating it. The microstructure is characterized by using optical microscopy, scanning electron microscopy, X‐ray diffraction, energy‐dispersive spectroscopy, and electron backscattered diffraction (EBSD). The microstructure shows the columnar dendritic structure elongated in the build direction. No cracks or porosity are observed in the structure. Average Vickers hardness for low, medium, and high heat input conditions are 146.6, 162.1, and 163.5 HV, respectively. There is an increasing trend of microhardness value along the deposition height, which can be attributed to the difference in secondary dendritic arm spacing and the formation of precipitates. The tensile strength of the specimen is comparable to the conventional and additively manufactured structures. EBSD analysis confirms that possible subgrains are responsible for good mechanical properties at room temperature. In the majority of the tensile samples, the failure mechanism has been identified as a ductile fracture. The mechanical characteristics fluctuate with locations in each of the thin walls, suggesting anisotropy in the deposits.

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“…As a result, it has been extensively used in the construction of superconducting radiofrequency (SRF) cavities in superconducting industry. Electron beam welding (EBW) in ultra-high vacuum is the best option for the joining of niobium components due to the high melting point of niobium and the requirement for high purity in weld [2][3][4][5]. In addition to the superconducting cavities, electron beam welding is also used in the joining of mono-filamentary pure niobium wires in the superconducting gravimeters due to low impurities in EBW joint [6], which guarantee good superconducting properties of niobium.…”

Section: Introductionmentioning

confidence: 99%

A new method for simulating electron beam welding process of niobium sheets with beam oscillation

Tao

Wu²,

Liu³

et al. 2023

Mater. Res. Express

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The construction of pure niobium superconducting radiofrequency (SRF) cavities requires the use of electron beam welding (EBW), particularly the welding in the equatorial region. The prediction of residual stress and welding distortion with high precision is important for the design of welding tooling and the optimization of welding parameters due to the detrimental influence that welding deformation and residual stress have on the performance of the SRF cavities. However, the EBW of the equator region is carried out with beam oscillation, a suitable simulation approach for the mechanical analysis of oscillating EBW received less attention. In this study, a novel heat source with two reverse 2D Gaussian heat source was created for the finite element method (FEM) simulation of EBW with beam oscillation. Additionally, a computational fluid dynamics (CFD) simulation of the molten pool was run as a guide for adjusting the parameters of the designed heat source. The FEM simulation with 2D Gaussian heat source was taken as a comparison. An EBW experiment of niobium sheets was performed for the validation of weld width, residual stress and welding distortion. The simulated molten pool of this model has a wider width, which is considerably closer to the actual measurement, and the thermal results reveal a smoother temperature gradient in the joint simulated with the proposed heat source. The mechanical results demonstrate that the estimation of the residual stress distribution and welding contradiction by the designed model are likewise more in accordance with the outcomes of the experiment. In the future, the oscillating EBW of sheet metal made of additional materials will be simulated using the suggested method.

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Effect of beam current on the microstructure, crystallographic texture and mechanical properties of electron beam welded high purity niobium

Cited by 15 publications

References 47 publications

Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness

Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness

Investigations of Microstructure and Mechanical Properties in Wire + Arc Additively Manufactured Niobium–Zirconium Alloy

A new method for simulating electron beam welding process of niobium sheets with beam oscillation

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