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Characteristics of multi-pass narrow-gap laser welding of D406A ultra-high strength steel
摘要： A universal and applicable method to predict bonding quality in narrow-gap laser beam filler wire welding of D406A ultra-high strength steel was presented. Defect-free joint could be achieved under the predicted optimal welding condition, while the production efficiency of narrow-gap laser beam filler wire welding under optimized welding condition was about 3.75 times that of traditional tungsten arc welding currently used in practical industry. Compared with the tungsten arc welding joint, microstructure in the fusion zone of laser welded joint was more uniform, which brought out a less fluctuation in the microhardness of fusion zone along the thickness direction. The tensile strength of as-welded laser welding joint was slightly higher than that of as-welded tungsten arc welding joint while the elongation of the former increased by 15.9% over that of the latter. A binocular stereo three-dimensional scanning method was adopted to compare the residual distortion of D406A joints between laser welding and tungsten arc welding. Notably, the distortion of laser welded joint was about 21% of that of the tungsten arc welding joint. Narrow-gap laser filler wire welding is a feasible substitute for conventional tungsten arc welding in the fabrication of welded construction of D406A steel.
关键词： ultra-high strength steel,welding distortion,filler wire,narrow-gap laser beam welding,microstructure
更新于2025-11-28 14:24:20
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Copper-Based Volumetric Filler Dedicated for Ag Paste for Depositing the Front Electrodes by Printing on Solar Si Cells
摘要： In this work we present research results on a new paste NPCuXX (where: NP—new paste, CuXX—component, XX—a modifier consisting of Ni and other important elements) based on a copper composite (CuXX) for fabrication of front electrodes in silicon solar cells. The CuXX composite is obtained by chemical processing of copper powder particles and can be used in two ways: as an additive to commercially available paste or as a base material for a new paste, NPCuXX. The CuXX offers the possibility to exchange up to 30 and 50 wt.% Ag into Cu, which significantly decreases the solar cells material costs, and therefore, the overall solar cell price. Emphasis was placed on a proper mass suitable fabrication process of the CuXX component. The NPCuXX paste has been applied both to conventional cell structures such as aluminum-back surface field (Al-BSF) and passivated emitter and rear contact (PERC), and finally solar cells with front electrodes deposited by screen-printing method were fabricated and characterized by current-voltage techniques. This paper reports the first implementation of the copper volumetric material into a screen print paste used in a high-temperature metallization process to fabricate the front contacts of Si solar cells with a highest fill factor of 77.92 and 77.69% for the abovementioned structures, respectively.
关键词： crystalline silicon solar cells,front electrode,copper-based volumetric filler
更新于2025-11-14 17:04:02
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Mechanically Enhanced Electrical Conductivity of Polydimethylsiloxane-Based Composites by a Hot Embossing Process
摘要： Electrically conductive polymer composites are in high demand for modern technologies, however, the intrinsic brittleness of conducting conjugated polymers and the moderate electrical conductivity of engineering polymer/carbon composites have highly constrained their applications. In this work, super high electrical conductive polymer composites were produced by a novel hot embossing design. The polydimethylsiloxane (PDMS) composites containing short carbon fiber (SCF) exhibited an electrical percolation threshold at 0.45 wt % and reached a saturated electrical conductivity of 49 S/m at 8 wt % of SCF. When reducing the sample thickness from 1.0 to 0.1 mm by the hot embossing process, a compression-induced percolation threshold occurred at 0.3 wt %, while the electrical conductivity was further enhanced to 378 S/m at 8 wt % SCF. Furthermore, the addition of a second nanofiller of 1 wt %, such as carbon nanotube or conducting carbon black, further increased the electrical conductivity of the PDMS/SCF (8 wt %) composites to 909 S/m and 657 S/m, respectively. The synergy of the densified conducting filler network by the mechanical compression and the hierarchical micro-/nano-scale filler approach has realized super high electrically conductive, yet mechanically flexible, polymer composites for modern flexible electronics applications.
关键词： compression-induced percolation threshold,synergy,electrical conducting network,hybrid filler,forced assembly
更新于2025-09-23 15:22:29
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Study on the Droplet Transition Models in Laser Welding with Filler Wire
摘要： This study is intended to examine the droplet transition in the welding process. Tests were performed using a high-speed camera to assess the effect of the vertical distance between the laser–wire intersection and workpiece (H) on droplet transition. Meanwhile, forces on the droplet were analyzed to evaluate the transition model during laser welding with filler wire. The results showed transition frequency, that droplet size and forces of the model all changed with H level changing. Droplet transition and the welding process showed stability at an H level of 1 mm. Based on the liquid bridge transition model, the droplet was transferred to the molten pool in the state of balance, while the droplet entered into the molten pool under non-equilibrium state during globular transition.
关键词： Droplet transition,Laser welding with filler wire,Vertical distance between the laser–wire intersection and workpiece,Force analysis of droplet
更新于2025-09-23 15:21:01
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Influence of Plasma Transfer Arc Cladding of NiCrBFe filler powder on microstructure and tensile properties of Titanium Grade 2 and Ti 6Al-4V alloy dissimilar joint prepared by laser beam welding
摘要： The present investigation deals with the effect of Plasma Transfer Arc Cladding (PTAC) of 60%Ni30%CrB10%Fe filler powder on microstructure and tensile properties of Titanium Grade 2 and Ti 6Al-4V alloy dissimilar joint done by laser beam welding. In laser beam welding, full depth of penetration was achieved using the laser beam power of 1300 W, welding speed of 200 mm/min and focus distance of 10 mm. Tensile studies showed that all the failures occurred in the fusion zones of as-welded, dissimilar weldments and PTAC coated samples. Failure analysis was performed using Comsol software and the results were obsersed as well-in accordance with the experimental results. Finite element studies showed the better accuracy results while comparing both experie-mental and simulation results. The microstructure and mechanical properties studies were conducted on as-welded, dissimilar weldments and PTAC coated samples by scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), and X-ray diffraction (XRD) respectively. XRD displayed the slight presence of compressive residual stress in PTAC coated samples. The microstrcture studies conducted at the fusion zone revealed that more amount of coarse grain boundaries were converted into α-Fe. The avearge heat inputs (Hi) were applied in the coated samples that converted the α + β phase structure into TiNi + TiCrFe boundarys. PTAC coated samples showed the average hardness value of 313 HV and dissimilar weldments exhibited the hardness value of 290 HV. The present study concluded that the corrosion resistance of coated materials was improved owing to the better tensile and bending strength of material.
关键词： Mechanical Properties,Plasma Transfer Arc Cladding,Finite element analysis,NiCrBFe filler powder,Laser beam welding
更新于2025-09-23 15:21:01
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Filler metal distribution and processing stability in laser-arc hybrid welding of thick HSLA steel
摘要： Welds made by high power laser beam have deep and narrow geometry. Addition of filler wire by the arc source, forming the laser-arc hybrid welding (LAHW) process, is very important to obtain required mechanical properties. Distribution of molten wire throughout the entire weld depth is of concern since it tends to have low transportation ability to the root. Accurate identification of filler metal distribution is very challenging. Metal-cored wires can provide high density of non-metallic inclusions (NMIs) which are important for acicular ferrite nucleation. Accurate filler distribution can be recognized based on statistical characterization of NMIs in the weld. In the present study, it was found that the amount of filler metal decreased linearly towards the root. The filler metal tends to accumulate in the upper part of the weld and has a steep decrease at 45–55 % depth which also has wavy pattern based on longitudinal cuts. Substantial hardness variation in longitudinal direction was observed, where in the root values can reach > 300 HV. Excessive porosity was generated at 75 % depth due to unstable and turbulent melt flow based on morphology of prior austenite grains. The delicate balance of process parameters is important factor for both process stability and filler metal distribution.
关键词： Filler metal distribution,Microstructure,Thick steel,Non-metallic inclusions,High strength steel,Mechanical properties,Laser-arc hybrid welding
更新于2025-09-23 15:19:57
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Preparation of highly thermally conductive and electrically insulating PI/BNNSs nanocomposites by hot-pressing self-assembled PI/BNNSs microspheres
摘要： Traditional polymer-based thermally conductive composites with randomly distributed fillers always yield an undesired heat removal due to the lack of efficient heat transfer pathways. Thus, realization of rational and ordered distribution of thermally conductive nanofillers in polymer matrix is believed to be significant for obtaining a desirable thermal conductivity. Herein, a series of thermally conductive polyimide/boron nitride nanosheets (PI/BNNSs) composites with a highly ordered BNNSs network have been successfully prepared. For achieving an uniform dispersion and high orientation of BN nanosheets in PI matrix, self-assembled PI/BNNSs complex microspheres were firstly prepared via the van der Waals interaction, and then these complex microspheres were further hot-pressed at the Tg of PI matrix, which rendered the alignment of BNNSs during the deformation of complex microspheres and built an efficient heat transfer pathway. As a consequence, the resultant composites possess a much higher in-plane thermal conductivity up to 4.25 W/mK with 12.4 vol% oriented BNNSs than those of pure PI and random distribution composite (0.85 W/mK for pure PI and 1.3 W/mK for the PI/random BNNSs-12.4). Meanwhile, these nanocomposites present excellent electrically insulating properties, improved dimensional stabilities and good thermal stabilities. This facile method provides a new way to design and fabricate highly thermally conductive PI-based composites for applying in heat dissipation of modern portable and collapsible electronic devices.
关键词： Boron nitride nanosheets,Polyimide,Complex microspheres,Hot-pressing,Filler orientation
更新于2025-09-23 15:19:57
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Fluoroalkyl POSS with Dual Functional Groups as a Molecular Filler for Lowering Refractive Indices and Improving Thermomechanical Properties of PMMA
摘要： The dual-functionalized polyhedral oligomeric silsesquioxane (POSS) derivatives, which have the seven fluorinated alkanes and the single acrylate ester on the silica cube, were designed as a filler for lowering the refractive index (RI) and improving thermomechanical properties in poly(methyl methacrylate) (PMMA). The desired dual-functionalized POSS fillers were prepared, and because of its high miscibility, homogeneous films were readily obtained, by the casting method, with the mixture solutions containing the modified POSS and the polymers. From optical measurements, it was found that the larger effects of lowering the RIs of the PMMA matrices were observed from the modified POSS than those of the octa-substituted POSS derivatives with the homogeneous substituents. It should be mentioned that the degradation temperatures and the storage moduli were able to be greatly elevated by loading the present POSS fillers. Finally, it was demonstrated that the methacrylate ester-tethered POSS should be the most effective filler for modulating PMMA (?n = ?0.020, ?Td20 = +53 °C, ?E’/E’ = +72%).
关键词： low refractive material,thermal stability,fluoropolymer,filler,POSS
更新于2025-09-19 17:15:36
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Comparison of laser-MIG hybrid and autogenous laser welding of M250 maraging steel thick sectionsa??understanding the role of filler wire addition
摘要： The present work is directed towards understanding the role of filler addition in laser-MIG hybrid welding (LHW) process as compared with that in autogenous laser welding (ALW) process during welding of 10-mm-thick maraging steel plates. Addition of filler wire is beneficial in improving the edge bridging between the parts to be welded and also in improving the fusion zone microstructure. Single-pass LHW of the 10-mm-thick maraging steel plates was performed using a combination of 3.5-kW CO2 laser and synergic pulse MIG welding power source at a welding speed of 1 m/min. MIG filler wire with reduced solutes such as Mo and Ti contents was used for the LHW process. Simultaneously, double-sided single-pass ALW of similar plates was performed. The role of filler wire addition on the microstructure and mechanical properties of the LHW fusion zone (FZ) was studied and compared with that of ALW FZ. The usage of filler wire resulted in less solutes in the LHW FZ after welding, and hence, the volume fraction of “reverted austenite (RA)” formed during aging was minimized when compared with ALW FZ. During transverse weld tensile testing, the ALW welds yielded higher tensile properties when compared with the LHW weld due to their fine grain structure and high number density of precipitates. Whereas the KIc fracture toughness of the ALW FZ was low with the KIc value of 49.5 MPa√m due to the presence of the high amount of RA as compared with LHW which exhibited the KIc value of 77.5 MPa√m. The study vividly brings out the advantages of LHW process in improving the microstructure of the fusion zone due to the addition of filler wire.
关键词： M250,Laser,Maraging,Filler,Welding,Hybrid,Fusion
更新于2025-09-19 17:13:59
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Efficient Charge Transfer and Carrier Extraction in All-Polymer Solar Cells Using an Acceptor Filler
摘要： All-polymer solar cells (all-PSCs) exhibit considerably improved mechanical and thermal stability than their polymer-fullerene counterparts. Despite their advantages, the power conversion efficiencies of all-PSCs are still lower than those of polymer-fullerene PSCs. In this study, we demonstrate that introducing a small amount of fullerene or nonfullerene acceptors as filler into the photoactive layer of PBDBT:N2200 all-PSCs can enhance charge transport properties, thereby the device performance. An appreciable enhancement (~21%) in the power-conversion-efficiencies (PCEs) of all-PSCs, from 6.13% to 7.42%, is obtained when fullerene with the amount of 25 wt% PBDBT is added. The performance improvement is primary from the enhanced short circuit current density (Jsc), which can be attributed to the enhanced exciton dissociation, reduced charge recombination, and balanced charge transport in the prescence of the fullerene filler. Similar behavior is also observed when fullerene is replaced by ITIC molecules. Importantly, the fullerene filler shows a negiligible effect on the device storage and light-soaking stability. Therefore, all-PSCs incorporating a proper selected acceptor filler is an efficient way to improve device performance without sacrificing stability. We believe that our study can pave a useful approach for developing stable and high performance PSCs.
关键词： filler,all-polymer solar cell,charge transport,ternary,charge extraction
更新于2025-09-19 17:13:59