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Simulations of microstructure coupling with moving molten pool by selective laser melting using a cellular automaton
摘要： Alloys produced by the selective-laser-melting process have excellent mechanical properties and their microstructures are significantly different from conventional cast alloys. In this paper, a model for predicting alloy microstructure coupling with heat transfer and a moving molten pool was developed using a cellular automata method, and the microstructure morphology and formation mechanism were numerically investigated. The growth kinetics of the solid/liquid interface is driven by the thermodynamic, composition and curvature undercooling, and the growth rate is computed by the Kurz-Giovanola-Trivedi model. The thermal history, cooling rate, molten pool, solidified track, grain growth, and undercooling were qualitatively analyzed by using the developed model. A complex dendritic growth mechanism including homogeneous and heterogeneous nucleations, competitive growth, and epitaxial growth was presented, and the effects of scanning speed, scanning spacing, and pre-heating temperature on the microstructure were examined. The results indicate that the cooling rate is approximately 105–106 K/s during the solidification, the equiaxed crystals increase with either increasing the pre-heating temperature or reducing the scanning speed. The epitaxial columnar grains become longer and narrower with increasing scanning spacing.
关键词： Dendritic solidification,Microstructure,Simulation,Selective laser melting
更新于2025-09-16 10:30:52
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Selective Laser Melting of Nanocomposite Ti-6Al-4V and TiC Powder
摘要： The paper presents the study results of the selective laser melting process of the Ti-6Al-4V alloy and nanosized powder TiC composition. The results of the particles morphology study of resulting powder composition after blending are presented. The microstructure and mechanical characteristics of the obtained composite material were studied. Study of microstructures using optical and electron microscopes were conducted.
关键词： Titanium Alloy Composite,Powder Metallurgy,Selective Laser Melting,TiC,Nanopowder
更新于2025-09-16 10:30:52
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Influence of Process Parameters on the Porosity, Accuracy, Roughness, and Support Structures of Hastelloy X Produced by Laser Powder Bed Fusion
摘要： The manufacture of highly complex components from nickel-based superalloys with laser powder bed fusion (L-PBF) technology can reduce the production costs parts with comparable microstructural and mechanical properties when compared to casting. The purpose of this study was to investigate the characteristics of samples produced in commercial Hastelloy X (with w% composition of 21Cr-18Fe-9Mo-0.7W-1.5Co-0.1C-1Si-1Mn-0.5Al-0.15Ti-bal.Ni) with an L-PBF process in terms of build density, accuracy, surface roughness, and interface area between the part and the support structures. Samples were obtained with a high density (99.88%), without cracks and with low surface roughness. From the analysis of the support structures, it emerged that the choice of the parameters between support structures, the lower face of the part (down-skin) and the internal area of the part (in-skin) is fundamental to the correct realization of these structures in order to avoid deformation of the components that is induced by thermal stresses during part building.
关键词： process parameters,nickel super-alloys,additive manufacturing,selective laser melting,Hastelloy X
更新于2025-09-16 10:30:52
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Microstructurea??Texturea??Mechanical Property Relationship in Alloys Produced by Additive Manufacturing Following Selective Laser Melting (SLM) Technique
摘要： Additively manufactured alloys produced by selective laser melting (SLM) exhibit different microstructure, texture and mechanical properties compared to their conventionally processed counterparts. The reason for this difference has been attributed to unique conditions that are met during processing through SLM. The differences are specific to the alloy system. Most influencing variable of SLM processing has been found to be the scanning strategy which comprises interlayer hatch rotation, build orientation, printing pattern (unidirectional, meander or checker board), etc. These variants lead to alteration of microstructure and crystallographic texture. Among the properties, yield strength of SLM-processed alloys has been found to be higher compared to their conventionally processed counterparts, which has been attributed to the finer microstructure and high defect density resulting from the process. On the other hand, ductility is on the lower side due to voids and porosity. The texture of SLM-processed materials shows characteristic features, which is dependent on materials and processing strategies. This further influences the properties. This paper deals with the evolution of microstructure, texture and mechanical properties for selected alloy systems, namely the alloys of iron, aluminium, and titanium, which have been most extensively studied after SLM processing.
关键词： Mechanical properties,Crystallographic texture,Additive manufacturing,Microstructure,Selective laser melting
更新于2025-09-16 10:30:52
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Prediction of Selective Laser Melting Part Quality Using Hybrid Bayesian Network
摘要： Additive manufacturing (AM) is gaining popularity because of its ability to manufacture complex parts in less time. Despite recent research involving designs of experiments (DOEs) to characterize the relationships between some AM process parameters and various part quality characteristics, to date, there seems to be no universally accepted comprehensive model that relates process parameters to part quality. In this paper, to support the goal of manufacturing parts right the first time, a Bayesian network in continuous domain is developed which relates four process parameters (laser power, scan speed, hatch spacing, and layer thickness) and five part quality characteristics (density, hardness, top layer surface roughness, ultimate tensile strength in the build direction and ultimate tensile strength perpendicular to the build direction). A machine learning algorithm is used to train the network on a database mined from a large number of publications with experimental data from parts built using 316L with selective laser melting. Using this Bayesian network, the user is able to enter a value for one or more known nodes or variables, and the network provides predictions on all the remaining nodes in the form of probability distributions. A method is developed whereby the user inputs are checked for reasonableness using an ??-dimensional convex hull, and if necessary a recommendation is returned based on user-defined weights. The network is validated by retaining a subset of the training data for testing and comparing the network’s predictions to the known values. Accuracy is optimized by continually re-training the network using parts built with a specific machine of interest. The industrial relevance of this research is outlined with respect to four current challenges in AM, including the length of time to determine optimal process parameters for a new machine, ability to organize relevant knowledge, quantification of machine variability, and transfer of knowledge to new operators.
关键词： Hybrid Bayesian Network,Selective Laser Melting Part Quality,Powder Bed Fusion,??-Dimensional Convex Hull,Predictive Model
更新于2025-09-16 10:30:52
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Cracking behavior and control of β-solidifying Ti-40Al-9V-0.5Y alloy produced by selective laser melting
摘要： A β-solidifying Ti-40Al-9V-0.5Y (at.%) alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting (SLM) in this study. The influence factors for cracking sensitivity, cracking behavior and crack inhibition mechanism were investigated. The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes. The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode. Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility of β-solidifying γ-TiAl alloys during SLM. On this basis, the formation and inhibition mechanism of solidification and cold cracking are proposed. Finally, the crack-free Ti-40Al-9V-0.5Y sample with fine equiaxed microstructures and favorable mechanical properties (microhardness of 542±19 HV, yield strength of 1871±12 MPa, ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57 %) can be produced by SLM. The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.
关键词： Phase transformation,Selective laser melting,Cracking behavior,Microstructure,β-solidifying γ-TiAl alloy,Cracking control
更新于2025-09-16 10:30:52
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Laser 3D printed bio-inspired impact resistant structure: failure mechanism under compressive loading
摘要： This work presents a comprehensive failure mechanism study of the bi-directionally corrugated (DCP) structures inspired by the telson of mantis shrimp. The DCP structures were fabricated by selective laser melting (SLM) with AlSi10Mg powder. The influence of key structural parameters, namely wave number (N), on the compressive behaviours, stress distribution, deformation modes and fracture mechanism of SLM-processed DCP components was systematically investigated. Results revealed that with the increase of wave number (N), the structural expansion effect became more obvious, which led to the disappearance of the plateau region on the compressive force-displacement curve, the decrease of specific energy absorption (SEA) growth rate and the energy absorption per periodicity cell. Three deformation modes were observed, namely full-folded mode (N = 4), transitional mode (N = 5), and global-buckling mode (N = 6). Finally, the fracture morphologies elucidated that the fracture mechanism changed from ductile fracture to brittle fracture with the increase of wave number.
关键词： bi-directionally corrugated panel,failure mechanism,selective laser melting,energy absorption,Bio-inspired
更新于2025-09-16 10:30:52
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Effect of heat treatment on the tensile behavior of selective laser melted Ti-6Al-4V by in situ X-ray characterization
摘要： Selective Laser Melted Ti-6Al-4V (as-SLMed) exhibits decreased yield strength, increased work hardening, and increased ductility after heat treatment at 730 °C (HT-730) or 900 °C (HT-900) for 2h. To understand the change of mechanical properties, in situ high energy X-ray diffraction (HEXRD) is used to examine the phase composition, load partitioning, slip system activity, and dislocation density evolution in all three specimens. The as-SLMed specimen is dominated by martensitic α?. After heat treatment, α? partly or fully decomposes into α+β, reducing the yield strength. In HT-730, β precipitates with confined size show much higher lattice strain than the α?/α matrix during deformation; in HT-900, the lattice strain difference is mostly eliminated. This is the main reason for the increased ductility in HT-900. From the lattice strain development, basal slip is identified as the easiest slip system in α?/α. Using an elasto-plastic self-consistent (EPSC) model, the critical resolved shear stress ratio between prismatic slip and basal slip (CRSSprismatic/CRSSbasal) is estimated to be 1.31 and 1.16 in the as-SLMed and the HT-900 specimens, respectively. The α phase in HT-900 is able to activate multiple slip systems and accumulate more dislocations during plastic deformation. This explains why HT-900 has higher work hardening rate than the other two specimens.
关键词： in situ X-ray diffraction,tensile deformation,Ti-6Al-4V,Selective Laser Melting
更新于2025-09-16 10:30:52
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Melt pool monitoring for laser beam melting of metals: inline-evaluation and remelting of surfaces
摘要： Laser Beam Melting of Metals (LBM-M) is an additive manufacturing technique that is applied successfully for the production of complex parts, small batch series and prototypes. In LBM metallic parts are generated layer by layer directly from sliced CAD data. For each layer a thin powder layer is deposited and subsequently irradiated by a focused laser beam which is guided by a galvanometer scanner. Due to variations in the powder stock, plain parameter sets and unresolved machine maturity problems, quality fluctuations are a major problem for a future series production. Surface roughness of parts during manufacturing is a quality issue. In this paper, we address it with a coaxial melt pool monitoring system and show a method for inline evaluation of surfaces by means of melt pool monitoring and the results of applied remelting strategies.
关键词： Laser Beam Melting,Additive Manufacturing,process stability,remelting,Selective Laser Melting,Melt pool Monitoring,Surface roughness,quality assurance
更新于2025-09-12 10:27:22
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Melt pool monitoring for laser beam melting of metals: assistance for material qualification for the stainless steel 1.4057
摘要： Laser Beam Melting of Metals (LBM-M) is an additive manufacturing technique that is successfully applied for the manufacturing of complex parts, small batch series and prototypes. In LBM metallic parts are generated layer by layer directly from sliced CAD data. For each layer a thin powder layer is deposited and subsequently, irradiated by a focused laser beam, which is guided by a galvanometer scanner. A major drawback of this relatively new manufacturing technology is a limited material portfolio. Today, the whole procedure of material qualification is time-consuming and resource intensive because a fast and reliable modelling of the process is not yet possible. In this work we are going to show the results of a qualification procedure applying a coaxial melt pool monitoring system to determine suitable processing parameters for a material, which has not yet been processed. In this work, a stainless steel material was exemplarily used to proof the feasibility. Furthermore, we are discussing the usability of this methodology for the material qualification in LBM-M in general.
关键词： Laser Beam Melting,Additive Manufacturing,Stainless Steel,Material Qualification,Quality Assurance,Selective Laser Melting,Process Stability,Melt pool Monitoring
更新于2025-09-12 10:27:22