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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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CoCr alloy processed by Selective Laser Melting (SLM): effect of Laser Energy Density on microstructure, surface morphology, and hardness
摘要： Selective Laser Melting (SLM) was used to realize Co-28Cr-6Mo samples. Several process parameters were considered, resulting in a wide range of Laser Energy Density (LED). The study was focused on the investigation of both process and material-related aspects, such as surface morphology, laser tracks dimension and defects formation mechanisms. In addition, macro (HRC) and microhardness (HV0.5) was assessed. A correlation between LED value and density, surface quality, microstructural features and hardness of SLM parts was defined. The final goal was to identify, for the biomedical Co-28Cr-6Mo alloy, the optimal LED window to be considered in order to maximize the overall quality of SLM parts.
关键词： Additive Manufacturing (AM),Biomaterial,Selective Laser Melting (SLM),Laser Beam Melting (LBM),Co28Cr6Mo,Co-based alloys
更新于2025-09-19 17:13:59
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Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples
摘要： Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.
关键词： laser polishing,additive manufacturing,selective laser melting,typical alloys,surface roughness
更新于2025-09-19 17:13:59
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Relating fracture toughness to micro-pillar compression response for a laser powder bed additive manufactured bulk metallic glass
摘要： A Zr-based bulk metallic glass produced using selective laser melting (SLM) was compared to the same alloy fabricated using traditional suction-casting. Analysis of the fracture toughness and mechanism through single edge notched beam bending experiments show a significantly reduced damage tolerance for the laser-processed material (KQ ~ 138.0 ± 13.1 → 28.7 ± 3.7 MPa √m), even though X-ray diffraction and microhardness responses were identical. Uncovered here using uniaxial quasistatic micro-pillar compression, as-cast samples more readily undergo shear transformations (evidenced through discrete load drops) below the nominal 0.2% yield stress, which can be connected to the higher macroscopic toughness. Differential scanning calorimetry demonstrated that the increased barrier to shear transformation for the SLM material could not be explained by the relative relaxation states. Rather, it is attributed to the greater dissolved oxygen concentration in the laser-processed material, which is postulated to decrease atomic mobility in the structure and thereby increase the activation energy required to initiate shear transformations.
关键词： fracture toughness,metallic glass,amorphous materials,additive manufacturing,selective laser melting,micromechanics
更新于2025-09-19 17:13:59
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Additive Manufacturing of Three-dimensional Metal-glass Functionally Gradient Material Components by Laser Powder Bed Fusion with In situ Powder Mixing
摘要： Existing commercial three-dimensional (3D) printing systems based on powder bed fusion approach can normally only print a single material in each component. In this paper, functionally gradient materials (FGM) with composition variation from a copper alloy to a soda-lime glass were manufactured using a proprietary nozzle-based multi-material selective laser melting (MMSLM) system. An in situ powder mixing system was designed to mix both metal and glass powders at selective ratios and the mixed powders were dispensed with an ultrasonic vibration powder feeding system with multiple nozzles. From the cross section analysis of the gradient structures, glass proportion increased gradually from the metallic matrix composite (MMC), transition phase to ceramic matrix composite (CMC). The pure copper alloy joined the MMC part and the pure glass phase penetrated into the CMC part during laser processing, which anchored the glass phase, as the main mechanism of combining pure metal and pure glass by FGM in 3D printed parts. From results of indentation, tensile and shear tests on the gradient material samples, it showed that mechanical properties of the FGM gradually changed from ductility (metal side) to brittle (glass side). The weakest part of the FGM structure occurred at the interface between transition phase and the CMC, which was also the interface between the ductile and brittle phases.
关键词： copper-glass,Powder Bed Fusion,horizontal gradient structure,multi-material selective laser melting,functionally gradient materials
更新于2025-09-19 17:13:59
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Evaluation for multiple processing parameters in selective laser melting based on an integration of mesoscale simulation and experiment method
摘要： Selection reasonable processing parameters for the metallic product by selective laser melting (SLM) is a significant issue to improve the performance of the final product. The optimization for the performance of the product is caused by the comprehensive effect of multiple processing parameters instead of a single parameter. It is urgent to propose a method for evaluating this comprehensive effect, furthermore, providing reasonable processing parameters. In this study, the mesoscopic features (molten pool morphology, free surface, porosity distribution, etc.) under different processing parameters are analyzed. Meanwhile, a powder scale thermal-fluid coupled model is established considering the randomly distributed powder bed and the complex physical phenomena within the molten pool. The simulation results are compared with the results characterized by multiple experimental methods. The integration of simulation and experiment results show that a fast scanning velocity or a large hatch spacing would decline the quality of the final product. A high energy density could decrease the roughness of the free surface but increase the porosity. Selecting a moderate energy density through a comprehensive comparison of multiple indicators is critical to evaluate the quality of metallic products by SLM.
关键词： mesoscopic features,comprehensive effect,multiple processing parameters,integration of simulation and experiment,selective laser melting
更新于2025-09-19 17:13:59
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Influence of manufacturing orientations on the morphology of alloy 718 single struts manufactured by selective laser melting
摘要： Selective laser melting (SLM) is of great interest for manufacturing lightweight structures such as lattices. It allows a broad range of lattice topologies to be created. However, when manufacturing small struts, roughness, lack of dimensional accuracy, and porosity level can decrease their mechanical properties and thus affect the mechanical response of the entire structure. This study focuses on the high-resolution characterization of alloy 718 (UNS N07718) single struts (constitutive elements of the lattice) manufactured by SLM. Process parameters, strategy, and post-treatments remain constant while varying strut positions on the build plate and orientations. A methodology for the systematic characterization of 19 struts with high-resolution X-ray tomography has been developed. Different features related to the strut size, shape, waviness, roughness, and porosity are extracted. The analysis of those features when varying strut positions and orientations highlights the influence of each parameter. The build orientation is a first-order parameter influencing strut morphology as already referenced in the literature. This systematic study reveals also the influence of the in-plane orientation for inclined struts that alters their roughness, shape, and size.
关键词： Selective Laser Melting,Build orientation,X-ray tomography,Lattice structures,Single struts,In-plane orientation
更新于2025-09-19 17:13:59
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Influence of heat treatment temperature on the microstructural, mechanical, and wear behavior of 316L stainless steel fabricated by laser powder bed additive manufacturing
摘要： A metal component fabricated by additive manufacturing (AM) is generally required to be heat treated to enhance microstructural and mechanical aspects. This present study aims to contribute to the literature in understanding the effect of heat treatment and various heat treatment temperatures on as-built components fabricated by AM. In this study, various heat treatment temperatures were applied to 316L stainless steel specimens produced by selective laser melting (SLM) and the effects on the microstructure, microhardness, XRD response, porosity, and wear behavior were investigated. The microhardness, XRD, and wear response of SLM 316L were compared with those of wrought 316L. The results illustrate that the heat treatment temperature has a substantial effect on the evolution of microstructure, XRD response, and porosity. Our results also support the argument that the effect of porosity on wear behavior is more dominant than the effect on microhardness. It should also be noted that the wrought 316L stainless steel specimen shows much better wear resistance than SLM 316L specimen.
关键词： Wear behavior,Selective laser melting,Heat treatment,Porosity
更新于2025-09-19 17:13:59
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Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting
摘要： The influence that complex component geometries can have on microstructure formation is investigated in a rocket engine impeller fabricated of a Ti-6Al-4V alloy by selective laser melting (SLM). The SLM melt pool monitoring, indicative of the component’s thermal history during processing, is linked to the bulk mapping of martensite decomposition obtained by high energy synchrotron X-ray diffraction. In addition to the martensitic and lamellar microstructures typically obtained during SLM of Ti-6Al-4V, spheroidization is identified to take place in the component’s down-skin regions. Grain boundary migration may contribute to the latter effect. Small recrystallized grains form along grain boundaries.
关键词： Titanium alloys,X-ray diffraction,Microstructure,Selective laser melting,Synchrotron radiation
更新于2025-09-19 17:13:59
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Research on Post-processing Microstructure and Property of Titanium Components with Selective Laser Melting (SLM)
摘要： Additive manufacturing of titanium component holds promise to deliver benefit such as reduced cost, weight and carbon emissions during both manufacture and use. To capitalize on the benefits, it must be shown that the mechanical performance of parts produced by additive manufacturing can meet design requirement that are typically based on wrought material performance properties. Of particular concern for safety critical structures is the fatigue property of parts produced by additive manufacturing. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology’s potential extension to high-integrity applications. In this study, fatigue life (S-N) and fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied. The interaction between the directional as-fabricated SLM microstructure and FCG was investigated and compared to that of the hot isostatic pressing (HIP) specimens with and without the stress relief after fabricating with SLM.
关键词： Titanium Components,Selective Laser Melting (SLM),Hot Isostatic Pressing (HIP),Fatigue Property,Microstructure
更新于2025-09-19 17:13:59