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The Effect of Laser Power on the Microstructure of the Nb-Si Based <i>In Situ</i> Composite, Fabricated by Laser Metal Deposition
摘要： The Nb-Si in-situ composite samples were fabricated by laser metal deposition additive manufacturing technology from mechanically alloyed powders in vario-planetary ball mill. A laser metal of samples was carried out at various laser powers: 500 W, 1000 W, 1400 W. The microstructure of a sample grown at a laser power of 500 W consists of a solid solution of Nb, Nb3Si, and dendritic chains of Ti. When the laser power is increased to 1000 W, the volume fraction of silicides increases, the structural heterogeneity decreases. With further increase in laser power to 1400 W, Ti dissolves in Nb, dendritic chains disappear, Nb5Si3 silicide stabilizes.
关键词： Additive manufacturing,Nb-Si based alloy,Direct energy deposition
更新于2025-09-16 10:30:52
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Effects of laser additive manufacturing on microstructure and crystallographic texture of austenitic and martensitic stainless steels
摘要： Powder-fed laser additive manufacturing (LAM) based on directed energy deposition (DED) technology is used to produce S316-L austenitic, and S410-L martensitic stainless steel structures by 3D-printing through a layer-upon-layer fashion. The microstructural features and crystallographic textural components are studied via electron backscattering diffraction (EBSD) analysis, hardness indentation and tensile testing. The results are compared with commercial rolled sheets of austenitic and martensitic stainless steels. A well-developed <100> direction solidification texture (with a J-index of ~11.5) is observed for the austenitic structure produced by the LAM process, compared to a J-index of ~2.0 for the commercial austenitic rolled sheet. Such a texture in the LAM process is caused by equiaxed grain formation in the middle of each layer followed by columnar growth during layer-upon-layer deposition. A quite strong preferred orientation (J-index of 17.5) is noticed for martensitic steel developed by LAM. Large laths of martensite exhibit a dominant textural component of <011>//{111} in the α-phase, which is mainly controlled by transformation during layer-by-layer deposition. On the other hand, the martensitic commercial sheet consists of equiaxed grains without any preferred orientation or completely random orientations. In the case of the austenitic steel, mechanical properties such as tensile strength, hardness and ductility were severely deteriorated during the LAM deposition. A ductility loss of about 50% is recorded compared to the commercially rolled sheets that is attributed to the cast/solidified structure. However, LAM manufacturing of martensitic stainless steel structures leads to a considerably enhanced mechanical strength (more than double) at the expense of reduced ductility, because of martensitic phase transformations under higher cooling rates.
关键词： Directed energy deposition (DED),Laser additive manufacturing (LAM),Crystallographic texture,S316-L austenitic stainless steel,S410-L martensitic stainless steel
更新于2025-09-12 10:27:22
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Coaxial laser triangulation for height monitoring in laser metal deposition
摘要： The control of the height parameter plays a crucial role in the laser metal deposition (LMD) process. A mismatch between the deposition height increment and the process growth rate can generate geometrical inaccuracies as well as collisions. The paper presents a method based on triangulation for monitoring in-line the height on a LMD system composed of a coaxial deposition head, an anthropomorphic robot and a fiber laser. The measurement device is implemented within the deposition head, with a probe laser beam that is launched coaxially through the nozzle and focused directly on the melt pool at different positions depending on the standoff distance. The position of the probe spot is acquired through a coaxial camera and converted in relative height values. The system is demonstrated for the distance measurement over a range of some millimeters during the deposition of AISI 316L stainless steel. This method allows for high flexibility being independent on the deposition direction.
关键词： additive manufacturing,optical monitoring,directed energy deposition,laser triangulation
更新于2025-09-12 10:27:22
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Melt Pool Size Control Through Multiple Closed-Loop Modalities in Laser-Wire Directed Energy Deposition of Ti-6Al-4V
摘要： Sensing and closed-loop control are critical attributes of a robust 3D printing process, such as Directed Energy Deposition (DED), in which it is necessary to manage geometry, material properties, and residual stress and distortion. The present research demonstrates multiple modes of closed-loop melt pool size control in laser-wire based DED, a form of large-scale metal additive manufacturing. First, real-time closed-loop melt pool size control through laser power modulation was demonstrated for intralayer control of bead geometry. Aspects such as controller tuning, response time, interaction with primary process variables, and disturbance rejection are presented. Next, an interlayer trend in laser power during the printing of layered components was documented, which inspired the development of novel modes of control. A controller that modulates print speed and deposition rate on a per-layer basis was developed and demonstrated, enabling the control of either average melt pool size alone or average laser power in coordination with real-time melt pool size control. This work demonstrates that accumulated heat in components under construction can be exploited to maintain process stability as print speed and deposition rate are automatically increased under closed-loop control. This has major implications for overall production efficiency. Control modes are characterized in terms of their effect on local bead geometry, global part geometry, and interlayer effect on energy density, among other factors.
关键词： Directed Energy Deposition,Monitoring,Metal,Closed-Loop,3D Printing,Ti-6Al-4V,Lasers,Control,Additive Manufacturing,Melt Pool
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Superfilament Spatial Dynamics and Energy Deposition under Various Focusing Conditions
摘要： One of the distinctive features of femtosecond laser ?lamentation is intensity and plasma concentration clamping. Arising due to the dynamical competition between Kerr focusing and plasma defocusing this phenomenon limits the peak intensity to the values 1014 W/cm2 and plasma concentration level to 1016 – 1017 cm?3. Further increase of the beam power leads to the beam splitting and multi?lament formation rather than to an intense single ?lament with high plasma density. However it have been recently shown that fusing several ?laments by introducing additional weak focusing one can obtain signi?cant enhancement of energy deposition in the extended region around the focus resulting in higher plasma concentration and intensity [1,2,3]. This report aims to present the comprehensive picture of super?lament evolution including its formation from merging ?laments and dissipation stages. We discuss energy deposition during the multi?lament evolution and its dependency of the pulse energy as well as the in?uence of additional focusing conditions on super?lament formation.
关键词： femtosecond laser ?lamentation,super?lament,energy deposition,plasma concentration,focusing conditions
更新于2025-09-12 10:27:22
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Microstructure by design: An approach of grain refinement and isotropy improvement in multi-layer wire-based laser metal deposition
摘要： The additive production of metallic components with high-throughput is usually associated with high process temperatures and slow cooling rates. This typically results in strongly oriented columnar grain growth along the building direction of the structure having exceedingly large grain sizes. As a result, such structures show typically low strength and anisotropic mechanical behaviour in as-deposited condition. Consequently, post-processing is commonly performed to homogenize and eventually increase the mechanical properties of the deposited structures. In this regard, precise control of the applied process energy allows a modification of the local temperature distribution and cooling conditions during the additive manufacturing process, which strongly influence the resulting solidification microstructure. The aim of the present study is the development of an approach that allows to influence the solidification conditions in wire-based laser metal deposition of an Al-Mg alloy through specific adjustments of the laser irradiation. It was found that significantly different solidification microstructures in as-deposited condition can be achieved by adjusting the laser beam irradiance within a range resulting in conduction mode welding conditions while keeping the heat input constant. The application of high laser beam irradiances, close to the transition to keyhole mode welding, results in structures with a homogeneous large-grained solidification microstructure exhibiting a degree of anisotropy of around 12% between building direction and the direction of deposition. In contrast, the use of low laser beam irradiances close to the lower limit of stable melting, results in structures with a significantly refined microstructure. Consequently, an increase of yield strength of up to 16% and microhardness of up to 13%, as compared to structures processed with high laser beam irradiance, could be obtained. Moreover, the anisotropy of the as-deposited structure was reduced to a degree lower than 2%.
关键词： Direct Energy Deposition,Aluminium Alloy,Laser Metal Deposition,Additive Manufacturing,Laser Irradiance,Grain Refinement
更新于2025-09-11 14:15:04
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Internal Energy Deposition in Infrared Matrix-Assisted Laser Desorption Electrospray Ionization With and Without the Use of Ice as a Matrix
摘要： The internal energy deposited into analytes during the ionization process largely influences the extent of fragmentation, thus the appearance of the resulting mass spectrum. The internal energy distributions of a series of para-substituted benzyl pyridinium cations in liquid and solid-state generated by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) were measured using the survival yield method, of which results were subsequently compared with conventional electrospray ionization (ESI). The comparable mean internal energy values (e.g., 1.8–1.9 eV at a collision energy of 15 eV) and peak widths obtained with IR-MALDESI and ESI support that IR-MALDESI are essentially a soft ionization technique where analytes do not gain considerable internal energy during the laser-induced desorption process and/or lose energy during uptake into charged electrospray droplets. An unusual fragment ion, protonated pyridine, was only found for solid IR-MALDESI at relatively high collision energies, which is presumably resulted from direct ionization of the pre-charged analytes in form of salts. Analysis of tissue with an ice layer consistently yielded ion populations with higher internal energy than its counterpart without an ice layer, likely due to a substantially enhanced number of IR absorbers with ice. Further measurements with holo-myoglobin show that IR-MALDESI-MS retains the noncovalently bound heme-protein complexes under both native-like and denaturing conditions, while complete loss of the heme group occurred in denaturing ESI-MS, showing that the softness of IR-MALDESI is equivalent or superior to ESI for biomolecules.
关键词： Ambient ionization,Survival yield method,Internal energy deposition,Mass spectrometry imaging,Thermometer ions,IR-MALDESI
更新于2025-09-11 14:15:04
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Predictive Modelling of Residual Stresses for Single Bead P420 Laser Cladding onto an AISI 1018 Substrate
摘要： Research correlating the process parameters, bead geometry, and induced residual stresses is essential for addressing geometric and functional quality issues for laser cladding based surface treatment and additive manufacturing solutions. However, analysis of variance methods cannot be readily applied, as the residual stresses values vary based on their position within the clad bead or substrate. Experimental data is used to calibrate single bead finite element models, which in turn, are used to seed an artificial neural network model and an adaptive neuro fuzzy interference system (ANFIS) model. Preliminary results indicate that the ANFIS approach has potential.
关键词： Neural Network,Residual Stresses,Simulation,Metal,Direct Energy Deposition,Adaptive Neuro Fuzzy Interference System,Additive Manufacturing,Experimental
更新于2025-09-11 14:15:04