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Surface morphology evolution with laser surface re-melting in selective laser melting
摘要： Laser surface re-melting (LSR) is a promising method for improving the surface quality of parts fabricated via selective laser melting (SLM). In this research, LSR under different linear energy densities (LEDs) was conducted numerically and experimentally. Additionally, double LSR using an LED of 225 J/m was conducted, and the surface morphology, melt pool flow behavior, melt pool size, and thermal behavior was investigated. The results show that for LSR with a low LED, the maximum flow velocity and maximum temperature was rather low, such that the surface was not reconfigured sufficiently. Furthermore, the surface between adjacent scan paths may not be entirely re-melted with a low LED, because the melt pool width was insufficient. However, when the LED was high, the maximum temperature gradient was rather large, giving rise to cracks. For double LSR with a moderate LED, the surface morphology was quite smooth and did not contain obvious defects. The results indicate that LSR is a feasible method for improving the surface quality, and repeated LSR with a moderate LED and small hatch space is recommended in SLM.
关键词： Selective laser melting,Laser surface re-melting,Melt pool flow,Surface morphology evolution
更新于2025-09-19 17:13:59
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A convolutional neural network for prediction of laser power using melt-pool images in laser powder bed fusion
摘要： In laser powder bed fusion, a convolutional neural network could build a good regression model to predict a laser power value from a melt-pool image. To empirically validate it, we used the acquired image data from a monitoring system inside metal additive manufacturing equipment and optimally configured a convolutional network by the grid search of hyper-parameters. The proposed network showed only 0.12 % of test images were out of the criterion for judging the predicted laser power value to be reliable and showed more accurate results than deep feed-forward neural network in the prediction of laser power states unseen in training steps. We expect that the proposed model could be utilized to discover the problematic position in additive-manufactured layers causing defects during a process.
关键词： convolutional neural network,melt-pool image,process monitoring,metal additive manufacturing,laser powder bed fusion
更新于2025-09-19 17:13:59
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Beyond the Toolpath: Site-Specific Melt Pool Size Control Enables Printing of Extra-Toolpath Geometry in Laser Wire-Based Directed Energy Deposition
摘要： A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser wire-based directed energy deposition is demonstrated with a novel modification, i.e., site-specific changes to the controller setpoint were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary three-dimensional (3D) printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed.
关键词： closed-loop control,lasers,metal,directed energy deposition,additive manufacturing,3D printing,titanium,site-specific,melt pool size
更新于2025-09-19 17:13:59
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Luminescence of Cr3+/Yb3+ co-doped oxyfluoride silicate glasses for crystalline silicon solar cell down-conversion devices
摘要： Oxy?uoride silicate glasses co-doped with Cr3+ and Yb3+ ions were fabricated in this work. High △T (178–214 °C) value demonstrated that the thermal stability of the prepared glasses were better than tellurite and germanate glasses. X-ray di?raction (XRD) curves proved the amorphous nature of the glasses, the energy dispersive spectroscopy (EDS) analysis and Fourier Transform infrared spectroscopy (FT-IR) curves explored the network structure of glasses. The photoluminescence excitation (PLE) and photoluminescence emission (PL) spectra show that the glasses absorption peaks located at 430 nm (Cr3+:4A2g - 4T1g (P)) and 627 nm (Cr3+:4A2g - 4T2g), while the emission peak close to 1010 nm (Yb3+:2F5/2 -2F7/2), which meets the condition of energy down-conversion. Besides, the energy transfer e?ciency (ηCET = 33.5%) and the quantum cutting e?ciency (ηQE = 133.5%) were calculated from the measured decay curves. These values were higher than Cr3+/Yb3+ co-doped ?uorosilicate glass with incorporating of CaF2 (21.5% and 123.5%) and Tb3+/Yb3+ oxy?uoride glass (13.5% and 113.5%), indicating the prepared samples are conducive to the energy transfer from Cr3+ to Yb3+ ions. The experimental results reveal that the oxy?uoride silicate glasses have potential application prospects in crystalline silicon (c-Si) solar cells.
关键词： Oxy?uoride silicate glasses,Melt-quenching method,Down-conversion and near-infrared luminescence emission,Crystalline silicon (c-Si) solar cells
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO?? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18a??22, 2015)] International Congress on Applications of Lasers & Electro-Optics - The influence of electric-magnetic composite field on WC particles distribution in laser melt injection
摘要： The laser melt injection method is always used to prepare a metal-matrix composite (MMC) layer on the surface of a substrate. In the LMI process, the laser beam melts the surface layer of substrate locally while simultaneously injecting particles of additional material. In order to control the distribution of reinforced particles in an LMI layer, an electric-magnetic composite field can be applied to assist the laser melt injection process. The effect of electric-magnetic synergistic on the reinforced particles distribution in laser melt injection was investigated using experimental and numerical method. The spherical WC particles were used as the reinforced particles, because the regular shape was most close to the simulation conditions and good tracer performance in the melt flow. The distribution state of WC particles in longitudinal section was observed by SEM and computer graphics processing. Meanwhile, The trajectory of WC particles in the melt pool were simulated by a 2D model coupled the equations of heat transfer, fluid dynamics, drag force, Lorenz force and phase transition. The simulation results are compared with experimental data and show good agreement. The results indicated that, the effect of electric-magnetic synergistic on the reinforced particles distribution in laser melt injection was verified. The distribution of WC particles in LMI layer was influenced by the direction of Lorenz force induced by electric-magnetic composite field. When the Lorenz force and gravity force are in the same direction, the vast majority of particles are trapped in the upper region of laser melt injection layer, and when the Lorenz force and gravity force are in the opposite direction, most particles are concentrated in the lower region.
关键词： Laser melt injection,distribution,electric-magnetic composite field,Lorenz force,particles
更新于2025-09-19 17:13:59
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Processability of Atypical WC-Co Composite Feedstock by Laser Powder-Bed Fusion
摘要： Processing of tool materials for cutting applications presents challenges in additive manufacturing (AM). Processes must be carefully managed in order to promote the formation of In this study, for the ?rst time, a satelliting process is used to prepare a WCM-Co (12 wt.% Co) composite. Melting trials were undertaken to evaluate the consolidation behaviour of single tracks within a single layer. Tracks with continuous and relatively uniform surface morphology were obtained. These features are essential for high-quality AM builds in order to encourage good bonding between subsequent tracks within a layer which may reduce porosity within a 3D deposition. This study elucidates the formation of track irregularities, melting modes, crack sensitivity, and balling as a function of laser scanning speed and provides guidelines for future production of WCM-Co by laser powder-bed fusion.
关键词： WCM-Co,satelliting,melt mode,single tracks,laser-powder bed fusion (L-PBF)
更新于2025-09-16 10:30:52
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High-Speed Laser Melt Injection of Tungsten Carbide in Highly Conductive Copper Alloys
摘要： For the first time, metal matrix composite (MMC) layers on parts made of highly conductive copper alloys have been generated by laser melt injection (LMI). In order to ensure a sufficient absorption efficiency, different kinds of surface modification were investigated. Welding speeds up to 7.5 m/min can be obtained. When increasing the dispersing rate, the process efficiency, which is the product of absorption efficiency and thermal efficiency, increases. At high dispersing rates, some spherical fused tungsten carbide (SFTC) particles are slightly deformed or partly fused together without decreasing the hardness.
关键词： metal matrix composite,surface modification,laser melt injection,wear resistance
更新于2025-09-16 10:30:52
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Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder
摘要： In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.
关键词： steel,additive manufacturing,melt pool,overlap,scanning strategy,directed energy deposition,AISI 316L
更新于2025-09-16 10:30:52
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Conductive and convective heat transfer during welding of AISI316L stainless steel using pulsed Nd: YAG laser
摘要： Conductive and convective heat transfers during an autogenous butt joint welding of AISI 316L stainless steel sheets using pulsed Nd: YAG laser have investigated. An FEA based three-dimensional model was developed to receive the transient thermal responses across the weld pool and the predicted results are compared with experimental observations. The heat transfer in the keyhole region, melt ?ow directions around the keyhole and heat affected zone are computed for consecutive pulse irradiation during laser welding and the same was investigated on far with experiment. The temperature distribution have predicted in terms of inward heat ?ux and Paclet number to investigate the heat and mass transportation in the weld pool. These results have taken for discussion and found that has a close association with experimental results.
关键词： Peclet Number,Pulsed laser welding,Melt ?ow,316L Stainless steel,Moving heat source,Heat transfer
更新于2025-09-16 10:30:52
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Luminescent solar concentrators based on melt-spun polymer optical fibers
摘要： Luminescent solar concentrators (LSCs) collect incoming sunlight and direct it to a smaller-area photovoltaic cell. In the presented work, form factor and illumination angle-dependent performance of LSCs consisting of bi-component melt-spun fibers is demonstrated. Three thermoplastic polymers act as dispersing host material for the luminescent dye Lumogen Red 305 (LR305). Molecular dynamics simulations provide numerical access to Hildebrand solubility parameters, which are an estimate for the mixing compatibility of dye with polymer matrix. Actual emission intensity measurements from material samples are compared to Monte Carlo ray tracing simulations. Some samples show an increased absorption, which led to the hypothesis that there exist optically passive dye aggregates if the dispersion is not optimal. The best-performing polymer/dye pair is identified and used to melt-spin fibers. Geometrically defined bundles of LSC fibers are studied in a scenario of white light illumination and variation of illumination-angle. This experiment simulates a theoretical daily course-of-sun illumination in absence of atmospheric effects. We report optical conversion efficiencies of the prepared LSCs between 2% and 15%, depending on illumination angle and bundle geometry.
关键词： Polymer optical fibers,Melt spinning,Energy harvesting,Luminescent solar concentrators
更新于2025-09-16 10:30:52