“…The solidifying columnar grains become remelted and broken into small pieces, which leads to a more chaotic and dispersed dendrite grain structure [9, 19, 34, 35]. This kind of melt flow behaviour was also discussed in previous reports [19, 34, 35], some modelling work [37] and tracer atomic analysis [9] were also done by researchers to reveal the melt flow behaviour during laser welding with beam wobbling. Figure 12 Schematics diagram of melt flow and top surface grain structure morphology with different wobble patterns: (a) without wobble; (b) circular wobble; (c) figure-eight wobble.…”
Laser welding with beam wobbling was employed to weld X70 pipeline steel. The influence of beam wobbling on weld surface morphology, fusion zone microstructure, and microhardness was investigated. The formation of spatter was suppressed by beam wobbling using a beam with higher energy density. At a welding speed of 1.0 m min −1 , the weld metal produced with a circular laser wobble pattern contained more martensite but less ferrite, compared to that of static spot welded joint. The presence of more martensite led to the increase in fusion zone hardness. A softened region was found in the inter-critical heat-affected zone. The hardness of the softened region could be improved by increasing the welding speed (from 1.0 to 1.5 m min −1 ).
“…The solidifying columnar grains become remelted and broken into small pieces, which leads to a more chaotic and dispersed dendrite grain structure [9, 19, 34, 35]. This kind of melt flow behaviour was also discussed in previous reports [19, 34, 35], some modelling work [37] and tracer atomic analysis [9] were also done by researchers to reveal the melt flow behaviour during laser welding with beam wobbling. Figure 12 Schematics diagram of melt flow and top surface grain structure morphology with different wobble patterns: (a) without wobble; (b) circular wobble; (c) figure-eight wobble.…”
Laser welding with beam wobbling was employed to weld X70 pipeline steel. The influence of beam wobbling on weld surface morphology, fusion zone microstructure, and microhardness was investigated. The formation of spatter was suppressed by beam wobbling using a beam with higher energy density. At a welding speed of 1.0 m min −1 , the weld metal produced with a circular laser wobble pattern contained more martensite but less ferrite, compared to that of static spot welded joint. The presence of more martensite led to the increase in fusion zone hardness. A softened region was found in the inter-critical heat-affected zone. The hardness of the softened region could be improved by increasing the welding speed (from 1.0 to 1.5 m min −1 ).
“…More comprehensive coupled fluid–thermal or fluid–thermal–mechanical models were used to analyze the processes of laser welding of aluminum alloys [ 72 , 73 ], titanium alloys [ 74 ], steels [ 75 , 76 , 77 , 78 ] or various dissimilar joints, especially a combination of different steel grades [ 79 , 80 ] or Al, Mg, Ti, Cu and Fe alloys [ 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ].…”
The formation of dissimilar weld joints, including Al/Ti joints, is an area of research supported by the need for weight reduction and corrosion resistance in automotive, aircraft, aeronautic, and other industries. Depending on the cooling rates and chemical composition, rapid solidification of Al/Ti alloys during laser welding can lead to the development of different metastable phases and the formation of brittle intermetallic compounds (IMCs). The effort to successfully join aluminum to titanium alloys is associated with demands to minimize the thickness of brittle IMC zones by selecting appropriate welding parameters or applying suitable filler materials. The paper is focused on the numerical simulation of the laser welding–brazing of 2.0 mm thick titanium Grade 2 and EN AW5083 aluminum alloy plates using 5087 aluminum filler wire. The developed simulation model was used to study the impact of laser welding–brazing parameters (laser power, welding speed, and laser beam offset) on the transient temperature fields and weld-pool characteristics. The results of numerical simulations were compared with temperatures measured during the laser welding–brazing of Al/Ti plates using a TruDisk 4002 disk laser, and macrostructural and microstructural analyses, and weld tensile strength measurements, were conducted. The ultimate tensile strength (UTS) of welded–brazed joints increases with an increase in the laser beam offset to the Al side and with an increase in welding speed. The highest UTS values at the level of 220 MPa and 245 MPa were measured for joints produced at a laser power of 1.8 kW along with a welding speed of 30 mm·s−1 and a laser beam offset of 300 μm and 460 μm, respectively. When increasing the laser power to 2 kW, the UTS decreased. The results exhibited that the tensile strength of Al/Ti welded–brazed joints was dependent, regardless of the welding parameters, on the amount of melted Ti Grade 2, which, during rapid solidification, determines the thickness and morphology of the IMC layer. A simple formula was proposed to predict the tensile strength of welded–brazed joints using the computed cross-sectional Ti weld metal area.
“…Recent studies have focused on the simulation of computational fluid dynamics (CFD) model-based heat transfer and fluid flow in the molten pool with beam oscillation [24][25][26][27]. They discovered that the periodic keyhole movement and fluid flow, in addition to the heat transfer process involved in the TEP method, have an impact on the temperature field in the fusion zone.…”
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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