•Al lead and tabs used as current collectors in electric vehicle battery were laser-welded to different welding states.•The different joint structures exhibited no appreciable difference in the ...electrical resistance measured across the welded region.•Our study showed that extremely low resiatances are obtained even if the joint structures have narrow current paths.
In pouch-type Li-ion batteries used in electric vehicles, battery cell tabs are electrically connected to an external lead of the same substance. Laser welding is a promising technique for joining these materials. This study investigates the fundamental question of whether electrical resistance measurements can be used to reliably estimate the welding state. An Al lead (400 μm thick) was welded spot-by-spot to a stack of 30 Al tabs (each tab 13 μm thick) using a laser beam incident on the lead surface. By adjusting the laser irradiation conditions, three different welding states (shallow, intermediate, and deep states) were intentionally produced. However, these structures exhibited no appreciable difference in the resistance measured across the welded region. The resistance was on the order of 10−4 Ω regardless of the welding state. Simulations were conducted for various joint structures, including those with voids, to derive the current flow through the structures and joint resistances. The simulation results corresponded well with the experimental results. Our study indicates that the electrical estimation of the welding state is challenging, because extremely low resistances are obtained even if the lead and tab are locally connected with narrow current paths.
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•The difference change of weld bead geometry occurs in fiber and CO2 laser welding.•The melting efficiency in fiber laser and CO2 laser welding is analyzed.•Secondary dendrite arm ...spacing and cooling rate in two laser weldings is studied.•The second phase in two laser welding with different heat input is investigated.
A comparative study on the influence of fiber laser welding (FLW) and CO2 laser welding (CLW) on the weld bead geometry and the microstructure of fusion zone (FZ) of Inconel 617 was investigated. In CLW joints, the weld bead geometry is Y-type shape. In FLW joints, the weld bead geometry transforms from Y-type to I-type with the decrease of the heat input. The minimum heat input required to achieve the full penetration of the weldment in FLW is lower than the CLW. The melting efficiency in FLW is higher than that in CLW. From the top to the root regions, the secondary dendrite arm spacing (SDAS) in fiber laser welded FZ undergoes a smaller change than that in CO2 laser welded FZ. The elements of Ti, Mo, Cr and Co segregate into the interdendritic regions both in FLW and CLW process. The second phases in CLW with the highest input of 360J/mm are much larger and more than ones in FLW with the highest heat input of 210.5J/mm.
Brittle MoFe intermetallic compounds (IMCs) are usually fatal for the joining of Mo and steel. In the present work, Ni-free joining of Mo and stainless steel was successfully achieved by laser ...welding with CuTi filler metal. The entry of Mo element into the weld seam and the formation of MoFe IMCs was significantly suppressed. TiFe, TiFe2, Ti5Cr8Fe16, and Cu-Ti-Fe phases were found inside the weld and near the interface. The IMCs were separated by Cu matrix and no continuous layered IMCs were found. The brittle fracture characteristics of TiFe IMCs and plastic deformation of the Cu matrix was found on the fracture surface in the weld.
•Ni-free laser joining of Mo and stainless steel was achieved with CuTi filler metal.•The formation of MoFe compounds in the weld was significantly suppressed.•The TiFe, Ti-Cr-Fe and Cu-Ti-Fe phases were separated by Cu matrix.•No continuous layered intermetallic compounds were found.•Plastic fracture characteristics of Cu matrix was found in the weld.
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•Laser welding between a CoCrFeMnNi high entropy alloy and 316 stainless steel was performed.•Joint ductility increased from 5 to 10 % by changing the CoCrFeMnNi high entropy alloy ...from rolled to annealed condition.•The joints strength is preserved at ≈ 450 MPa regardless of the CoCrFeMnNi high entropy alloy condition.•The CoCrFeMnNi / 316 stainless steel joints can be considered for structural applications.
Dissimilar joining involving high entropy alloys is currently being explored to evaluate the suitability of these novel advanced engineering materials in structural applications. Recently, joining of a CoCrFeMnNi high entropy alloy to 316 stainless steel was successfully attempted. However, the joint ductility was limited by the lack of deformation experienced by the cold-rolled CoCrFeMnNi base material during tensile loading. In this work, it is shown that by simply changing the base material condition, from cold-rolled to annealed, it is possible to significantly improve the joint fracture strain from ≈ 5 to ≈ 10 %, while preserving the strength at ≈ 450 MPa. Using electron microscopy, high energy synchrotron X-ray diffraction and mechanical testing aided by digital image correlation, the microstructure evolution across the welded joint is assessed and correlated to its mechanical performance. Moreover, thermodynamic calculations considering the compositional changes across the fusion zone were used to predict the microstructure evolution of this region.
The predominant method for improving the mechanical characteristics of aluminum-lithium (Al–Li) alloys during laser welding is by regulating the transition from columnar crystals to equiaxed ...crystals. The transition is facilitated through the incorporation of TiC particles, which play a crucial role in augmenting the strength and toughness of the aluminum alloy. The inclusion of TiC particles offers a new opportunity to enhance the utilization of Al–Li alloys in laser welding procedures. The main aim of this study is to control the transition from columnar to equiaxed crystal structures by creating a TiC nanoparticle-reinforced aluminum alloy filler wire. This is intended to improve the properties of laser-welded joints. The study investigates the impact of different TiC particle contents on the microstructural characteristics. The presence of TiC particles is noted to enhance the transformation of columnar crystals into equiaxed crystals in the welded joints, resulting in a refined microstructure. The augmentation of particle content results in a notable reduction in the average grain size, decreasing from 78.25 μm to 37.15 μm. This alteration shifts the directional growth preference from specific crystallographic axes to a stochastic trajectory. Significantly, when the particle content reaches 0.6 wt%, remarkable enhancements in both tensile strength and elongation are evident, resulting in an ultimate tensile strength of 318 MPa and an elongation of 4.8 %. The dispersed configuration of TiC particles plays a pivotal role in hindering the movement of dislocations, consequently increasing the energy necessary for this mechanism. Moreover, the existence of these particles at grain boundaries impedes the propagation of cracks by altering the direction of the crack path, absorbing additional energy, and consequently improving toughness. An evident pattern emerges when examining higher particle concentrations, indicating that a decrease in ultimate tensile strength is concomitant with an increase in elongation.
As a lightweight material, the high-silicon aluminum alloy Al-25Si-4Cu-Mg has been widely used in aerospace, transportation and construction. Porosity is the most common welding defect in laser ...welding of high silicon aluminum alloy, and has a certain impact on the properties of high-silicon aluminum alloy. A comparative study of the continuous laser welding (CLW) and pulse laser welding (PLW) of Al-25Si-4Cu-Mg must be conducted to explore the influence of different laser energy output modes on welding. The TruPulse556 pulse lasers and IPG continuous lasers were used to perform the laser welding test in this study. Moreover, a comparative analysis of the PLW and CLW of Al-25Si-4Cu-Mg in terms of microstructure and mechanical properties, including the weld microstructure, hardness, the tensile properties, and porosity. The research shows that PLW inhibits the formation of porosity more effectively than CLW. The mechanical properties and microstructure of the Al-25Si-4Cu-Mg welded joint can be improved by PLW, which has significance to the research on the PLW of high-silicon aluminum alloy.
An all-silica Diaphragm-based miniature optical fiber pressure sensor based on the Fabry-Perot (FP) interferometric principle is proposed. The FP structure is composed of a single-mode fiber and a ...fiber capillary end face diaphragm by a CO2 laser welding. The fabrication process and parameter control of all-silicon diaphragm are introduced in detail, and the pressure performance test system of FP is set up. The experimental results show that the fiber optic FP sensor has good sensitivity and linearity to air pressure, the sensitivity can reach 9.48 pm/kPa when the pressure ranges from 0 to 200 kPa, and the linearity is 0.998. All-silica diaphragm-based fiber FP pressure sensor fabricated by CO2 laser melting capillary end face is more compact, easy to produce, and has great potential in the extreme harsh environment.
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•It was feasible to join Al/steel in butt joints using fiber laser welding.•The mechanism of the joints was analyzed in detail.•The thickness of IMCs layer should be controlled to ...obtain higher tensile strength.•The joints failed in the FeAl3 layer, rather than the Fe2Al5 layer.
Dissimilar metals of AA6013 aluminum alloy and Q235 low-carbon steel of 2.5mm thickness were butt joined using a 10kW fiber laser welding system with ER4043 filler metal. The study indicates that it is feasible to join aluminum alloy to steel by butt joints when zinc layer was hot-dip galvanized at the steel’s groove face in advance, and better weld appearance can be obtained at appropriate welding parameters. The joints had dual characteristics of a welding joint on the aluminum side and a brazing joint on the steel side. The smooth Fe2Al5 layer adjacent to the steel matrix and the serrated-shape FeAl3 layer close to the weld metal were formed at the brazing interface. The overall thickness of Fe–Al intermetallic compounds layers produced in this experiment were varied from 1.8μm to 6.2μm at various welding parameters with laser power of 2.85–3.05kW and wire feed speed of 5–7m/min. The Al/steel butt joints were failed at the brazing interface during the tensile test and reached the maximum tensile strength of 120MPa.
Laser welding (LW) thanks to its flexibility, limited energy consumption and simple realization has a prominent role in several industrial sectors. LW process requires careful parameters’ tuning to ...avoid generating internal defects in the microstructure or a poor weld depth, which reduce the joining mechanical strength and result in waste. This work exploits a supervised machine learning algorithm to optimize the process parameters to minimize the generated defects, while catering for design specifications and tolerances to predict defect generation probability. The work outputs a predictive quality control model to reduce non-destructive controls in the LW of aluminum for automotive applications.
This paper reports on a study involving examination of the geometry, microstructure and microhardness of welds produced on a 1.625mm thick Ti6Al4V titanium alloy using the IPG YLR-1000 fiber laser. A ...numerical model has been developed to predict the fusion zone (FZ), heat affected zone (HAZ) and microhardness of the weld. The thermal history from the multi-physics model is incorporated into a two-dimensional phase prediction model to predict the α′ martensite formation in the heat-affected zone and fusion zone. The multi-physics phase prediction model is applied to simulate the laser keyhole welding process with varying laser power and welding speed. It was observed that the weld geometry and microhardness predictions from the multi-physics model were in good agreement with the experimental data. The results show that the peak hardness consistently appear at the FZ and HAZ boundaries due to the high cooling rate. In addition, it has been found that laser welding speed has a profound influence on acicular α′ martensite formation leading to hardness change. Consequently, to minimize the weld hardening, use of lower power and lower welding speed parameters is recommended in the power range of 800–1000W and welding speed range of 1.73–4m/min.
