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Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718
摘要： Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.
关键词： additive manufacturing,laser blown powder directed energy deposition,spectroscopic system,in-process monitoring
更新于2025-11-21 11:01:37
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Numerical modeling of coaxial powder stream in laser-powder-based Directed Energy Deposition process
摘要： Laser-powder-based Directed Energy Deposition (DED) process has been used extensively and becomes more and more popular in part manufacturing, repairing and prototype fabrication. It offers an effective way to deposit material via simultaneous delivery of the powders of desired material and laser beam. Complex physical events take place during the process and have great impacts on the success of the process, in which powder stream and its interaction with laser beam play a crucial role. In this paper, a new comprehensive numerical model for powder stream dynamics and heating process is developed to describe the coaxial powder stream and its interaction with laser beam. Reynolds Averaged Navier-stokes (RANS) approach is used for turbulent continuum gas flow while a discrete phase model (DPM) is applied to describe the dynamic behavior of the powder. Two-way coupling approach is adopted to account for the momentum transfer between gas and powder. A new thermal model is developed for powder stream, in which the interaction between powder stream and Gaussian laser beam is modelled through a novel numerical submodel. The obtained results of powder stream are compared with the experimental results from published literature and show good agreement.
关键词： Laser beam,Directed Energy Deposition,Coaxial powder stream,Numerical modeling
更新于2025-09-23 15:21:01
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Influence of Static Magnetic Field on the Microstructure of Nickel-Based Superalloy by Laser-Directed Energy Deposition
摘要： The influence of a static magnetic field on microstructure evolution during laser direct energy deposition was studied. Our results reveal that dendrite spacing increases with increasing magnetic field flux density (MFFD). Moreover, electron backscatter diffraction results reveal that the epitaxial growth was preferred with increasing MFFD. We discuss these findings in terms of the influence of a magnetic field on melt convection and propose that an applied magnetic field effectively limits Marangoni convection.
关键词： microstructure,static magnetic field,laser-directed energy deposition,dendrite spacing,Marangoni convection
更新于2025-09-23 15:21:01
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Directed energy deposition of Al 5xxx alloy using Laser Engineered Net Shaping (LENS??)
摘要： Here, we present directed energy deposition (DED) of wrought-like Al 5xxx AlMg alloy by Laser Engineered Net Shaping (LENS?). A transition from an Al 5083 gas atomized powder feedstock to Al 5754 characteristics of the as-deposited material due to selective evaporation of Mg was observed. Density values obtained by X-ray micro-computed tomography (μ-CT) were compared to those obtained by the Archimedes method. The latter indicated a relative density as high as 99.26%. Possible origins of porosity are discussed. The as-deposited material was comprised of both equiaxed and columnar grains with no preferred crystallographic orientation and mean grain size of 36 μm. The Young's modulus, yield stress, ultimate tensile strength, fracture strain, Poisson's ratio, and total ultimate strain energy (toughness) were determined by uniaxial tensile tests combined with digital image correlation (DIC). Fractography complemented the mechanical testing. A pulse-echo ultrasonic non-destructive test was used to obtain more accurate values of the Young's and shear moduli and to adjust the value of the yield strength accordingly. The measured mechanical properties meet the requirements of international standards for wrought Al 5754 in its annealed condition.
关键词： Additive manufacturing (AM),Mechanical properties,Micro-computed tomography (μ-CT),Laser Engineered Net Shaping (LENS?),Directed energy deposition (DED),Aluminum alloys
更新于2025-09-23 15:21:01
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Design Principles of Narrow and Wide Bandgap-Based Betavoltaic Batteries
摘要： A Monte Carlo electron transport code PENELOPE was used to analyze beta particle energy deposition in semiconductors for titanium tritide and beryllium tritide. The source thickness was incorporated into the model in order to take into account the self-absorption of beta particles in the source material. Furthermore, an isotropic source was modeled with the full beta energy spectrum of tritium to make the beta particle transport method more realistic. The simulated results for a 0.4-μm-thick titanium tritide source with silicon carbide agreed well with the experimental results. The simulated results obtained for an optimized 2.5-μm-thick beryllium tritide source with silicon carbide was about two times higher than the power for a 0.4-μm-thick titanium tritide source with silicon carbide. An approximately two times higher short-circuit current density was obtained for beryllium tritide with silicon compared to silicon carbide. However, the power output density was about 10× higher for silicon carbide. The width of the depletion region for a p-type dopant concentration of 1×1019/cm3 and an n-type dopant concentration of 5×1014/cm3 is about 1.4 and 2.5 μm in silicon and silicon carbide, respectively. The estimated beta particle penetration depth is about 1.48± 0.015 and 1.03 ± 0.015 μm in silicon and silicon carbide, respectively. This suggests that the proper choice of dopant concentrations will achieve greater energy deposition in the depletion region, which in turn will increase the power output.
关键词： design principles of betavoltaic batteries,Beta particle energy deposition,self-absorption
更新于2025-09-23 15:21:01
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Collinear dual-pulse laser optical breakdown and energy deposition
摘要： A non-equilibrium model for laser-generated plasmas is used to represent collinear dual nano-second-pulse interactions. In the specific case considered, the breakdown is initiated with an ultraviolet (UV) laser pulse at 266 nm, which pre-ionizes the gas, and it is followed by a near-infrared (NIR) pulse at 1064 nm, which deposits significant energy into the ionized mixture. The model is validated against corresponding experiments, and simulation results are interrogated to understand key features of the plasma-kernel dynamics in the breakdown phase, and the initial post-breakdown vorticity and plasma-core decay.
关键词： energy deposition,laser-induced breakdown,non-equilibrium plasma,plasma dynamics,dual-pulse laser
更新于2025-09-23 15:19:57
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Dynamics of dual-pulse laser energy deposition in a supersonic flow
摘要： Dynamics of plasma generated by the dual-pulse laser in a supersonic flow was studied numerically. The mathematical model includes species, momentum, electronic, vibrational and translational energy equations for the multicomponent ionized air. The model examines temporal dynamics of the formed air plasma and how it affects the drag, pressure signature and vorticity generation in a supersonic flow around a wedge. We observed that nonequilibrium plasmas is more effective in the drag reduction compared with the simultaneous thermal energy addition. The maximum drag reduction of around 50% and the maximum drag coefficient reduction of 30% was attained through the dual-pulse laser energy deposition. Variation of the plasma spot orientation did not significantly influence the drag reduction. We suggested that the surface pressure changes were not controlled by the vorticity generation but occurred due to the density changes and the formation of the low–density plasma spot.
关键词： supersonic flow control,energy deposition,laser,numerical modeling
更新于2025-09-23 15:19:57
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Controllable photon energy deposition efficiency in laser processing of fused silica by temporally shaped femtosecond pulse: Experimental and theoretical study
摘要： Photon energy deposition plays a crucial role in femtosecond laser irradiation followed by chemical etching processing, which is an emerging technique for the better control of micro/nano structures on fused silica. In this study, we have experimentally and theoretically studied the controllable photon energy deposition in laser irradiation of fused silica by temporally shaped femtosecond laser pulse trains. The experimental result shows that the photon energy deposition efficiency could be either reduced or enhanced by adjusting the total fluence of shaped pulse trains. Furthermore, the sub-pulse interval and intensity ratio of temporally shaped pulse trains were revealed to play a critical role in photon energy deposition. The corresponding experimental observations are qualitatively explained by a plasma model that considers the free electron generation processes and corresponding feedback on the photon energy deposition.
关键词： Photon energy deposition,Femtosecond laser,Temporally shaped pulse,Chemical etching,Fused silica
更新于2025-09-23 15:19:57
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In-process measurement of melt pool cross-sectional geometry and grain orientation in a laser directed energy deposition additive manufacturing process
摘要： Understanding the behaviour of melt pool during laser directed energy deposition (L-DED) is essential for the prediction and control of process quality. Previous effort was focused on the observation of melt pool surface characteristics. In this paper, a coaxial imaging system was employed to determine the melt pool cross sectional geometry and to predict solidified grain orientation during a high deposition rate L-DED process. The image processing procedure, deposition track cross-sectional profile prediction and the relationship between melt pool shape and melt pool dynamics, and grain growth orientation were investigated. Results show that sharp melt pool edges can be obtained so that melt pool width can be predicted with an accuracy of more than 95%. The estimation method of melt pool length has an accuracy of 90%. With the experimental melt pool width and depth data, the cross-sectional profiles of deposited track are predicted at an accuracy of 92% and a good match with experimental data is obtained. The melt pool formation is found to be able to allow the prediction of crystal growth directions during solidification.
关键词： Melt pool dimension,Laser additive manufacturing,Track geometry,Laser directed energy deposition,Grain growth
更新于2025-09-23 15:19:57
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Laser-Assisted Machining of Ti-6Al-4V Fabricated by DED Additive Manufacturing
摘要： Recently, the commercialization of hybrid machine tools that combine directed energy deposition (DED) additive manufacturing (AM) technology and subtractive manufacturing (SM) has rapidly progressed. This technology trend has been developed to meet the market demand for processing quality (precision) and productivity, and to produce products such as lightweight parts, and complex and special functional parts, as well as to facilitate mold production and part repair. Compared to SM technology, metal AM technology has limitations in terms of surface quality and shape accuracy. Therefore, post-processing is necessary for the AM output. Laser-assisted machining (LAM) is an innovative hybrid technique in which surface quality and productivity can be improved by enhancing the machinability of difficult-to-cut materials. LAM studies have mainly been performed on titanium alloys, nickel based alloys and ceramic materials. However, except for ceramics, no high-strength material studies have been conducted to analyze the LAM process machining characteristics of workpieces fabricated by AM process. Therefore, in this study, LAM is applied to post-processing of output fabricated by AM of Ti-6Al-4V. DED device was developed using metal powder feeder and a laser. The Ti-6Al-4V workpieces were successfully fabricated through many tests. The cutting depth for LAM was selected through thermal analysis for LAM of the fabricated workpiece. Compared to the case of traditional machining without preheating, machining characteristics in LAM experiments were analyzed and property testing was performed.
关键词： Machining characteristics,Additive manufacturing,Directed energy deposition,Ti-6Al-4V,Laser-assisted machining
更新于2025-09-23 15:19:57