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Microstructure of a Tia??50??wt% Ta alloy produced via laser powder bed fusion
摘要： Ti–Ta alloys have been widely studied for biomedical applications due to their high biocompatibility and corrosion resistance. In this work, nearly fully dense and in situ alloyed Ti–50 wt% Ta samples were fabricated by the laser powder bed fusion (LPBF) of mechanically mixed powders. With increased exposure time, and thereby increased laser energy density, insoluble Ta particles were almost dissolved, and a Ti–50 wt% Ta alloy was formed. Cellular and dendritic structures were formed due to constitutional undercooling, which was caused by the high cooling rate of LPBF process. Both retained β phases and α″ phases were observed in the LPBFed Ti–50 wt% Ta alloy. The α″ phase was found at the boundary of the cellular structures, where the tantalum content was not high enough to suppress the bcc lattice transition completely but could suppress the β phase → α′ phase transition.
关键词： Cellular and dendritic structures,Phase transformation,Ti–Ta alloys,Laser powder bed fusion,Microsegregation
更新于2025-09-23 15:21:01
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Simulation-assisted analysis of microstructural evolution of Tia??6Ala??4V during laser powder bed fusion
摘要： A combination of a Multi-Phase Field model and an Orientation Field is proposed to describe the microstructure evolution induced by laser–material interaction in Laser Powder Bed Fusion (LPBF). The relevant phase transformations are covered by nucleation and growth processes driven by free enthalpy. An empiric correction is applied to the phase-field approach to reduce the grid resolution required for the numerical simulation. This contribution focuses on the LPBF processing of the titanium alloy Ti–6Al–4V. Particularly, the transition between β-titanium and melt is emphasized. The results are discussed and compared to measurements. A numerical correction can be applied to the MPF model to avoid a mesh introduct anisotopy in the crystal growth. The simulation shows the β-phase crystal growth with the (1 0 0) direction into the melt. The model for the phase transformation from β-phase to α-phase agrees with the XRD measurements.
关键词： Simulation,Orientation field method,Phase-field method,Selective laser melting,Volume of the fluid method,Laser powder bed fusion
更新于2025-09-23 15:19:57
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[The Minerals, Metals & Materials Series] TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings || Critical Quenching Rates After Solution Annealing: Peculiarities of Aluminuma??Silicon Alloys Fabricated by Laser Powder-Bed Fusion
摘要： Hot isostatic pressing is commonly used to reduce the porosity of (sand-)cast age-hardenable Al-alloys in order to meet the high quality requirements defined by aircraft and automotive industries. In order to establish additive manufacturing methods, such as laser powder-bed fusion (L-PBF), hot isostatic pressing can be utilized to reduce the anisotropic mechanical properties in as-built condition and at the same time eliminate porosity. For the cast aluminum alloy A356, a gas pressure of 75 MPa during hot isostatic pressing lowers the critical cooling rate required to achieve an oversaturated solid solution to about 1 K/s, which is significantly lower than the required quenching rate at atmospheric pressure (2–4 K/s). Thus, an oversaturated state of dissolved magnesium and silicon atoms within the aluminum matrix of cast alloys can easily be achieved in modern hot isostatic presses, thereby avoiding the necessity of a separate solution annealing step. In this work, we applied hot isostatic pressing followed by rapid quenching and direct aging to age-hardenable aluminum alloys processed by both sand casting and laser powder-bed fusion. It was shown that the proposed process of direct aging could be utilized for post-heat treatment of additively manufactured age-hardenable aluminum alloys to open up new fields of applications, for which components have to possess a high fatigue resistance.
关键词： Hot isostatic pressing,Critical cooling rate,Additive manufacturing,Fatigue resistance,Laser powder-bed fusion,Selective laser melting
更新于2025-09-23 15:19:57
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Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review
摘要： Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.
关键词： 17–4 stainless steel,heat treatment,microstructure,precipitation-hardened stainless steels,ferrite,selective laser melting,building atmosphere,defects,laser powder bed fusion
更新于2025-09-23 15:19:57
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Probing a novel heat source model and adaptive remeshing technique to simulate laser powder bed fusion with experimental validation
摘要： A finite element method based three-dimensional heat transfer model with adaptive remeshing is presented to simulate the building of multiple tracks and layers in laser powder bed fusion of metallic powders with enhanced computational competence. A dimensional analysis is undertaken to define the heat source dimensions as function of laser parameters and properties of alloy powder. The computational model is used to calculate the melt pool cross sections for multiple combinations of laser power and scanning velocities considering multi-track-multi-layer builds of SS316L powder. The computed results are verified extensively with the corresponding experimentally measured ones. The model is utilized further to examine its ability to predict defects such as melt track discontinuity and incomplete fusion between neighboring tracks and layers. Overall, the adaptive remeshing and the proposed heat source expression could significantly enhance the model competence by reducing the computational time and memory while maintaining the accuracy of results in simulating laser powder bed fusion of multiple tracks and layers.
关键词： Selective laser melting (SLM),Pool dimensions,Adaptive remeshing,Laser powder bed fusion (L-PBF),Melt pool defects,SS316L alloy
更新于2025-09-23 15:19:57
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Accuracy of complex internal channels produced by laser powder bed fusion process
摘要： Additive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite-communication microwave systems. These systems can have complex shapes and make traditional ?nishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces are as close as possible to the tolerance of the ?eld of application. In this study, a complex component, a unique waveguide device with bending, twisting and ?ltering functionalities, has been designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Three di?erent prototypes with three di?erent curvature (R of 50 mm, 40 mm and 30 mm), operating in Ku/K band, have been manufactured and tested showing a very good agreement with the desired performances. Using 3D scan data, the internal deviations from the CAD model have been evaluated showing an average deviation of the internal areas of about 0.08 mm, 0.046 mm and 0.023 mm from the CAD model for the R of 50 mm, 40 mm and 30 mm respectively The surface roughness measured in the internal channel is about Ra (arithmetic average roughness) of 8 μm ± 1.3 μm and Rz (average maximum height of the roughness pro?le) of 62.3 μm ± 0.34 μm.
关键词： Integration waveguide subsystem,Additive manufacturing,Laser powder bed fusion
更新于2025-09-23 15:19:57
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In-situ formation of ceramic layer on Mo-based composites via laser powder bed fusion
摘要： Poor oxidation resistance is a longstanding disadvantage of Mo-based materials for ultrahigh-temperature applications. In this study, we developed a facile strategy for depositing an in-situ ceramic layer on the surface of Mo-based composites via laser powder bed fusion (L-PBF) using Mo-based alloy powders covered with uniform Al2O3 nanoparticles and bridged by functionalized carbon nanotubes. The surface layer consisted of an α-Al2O3 matrix with a dispersed TiC phase and had a controllable thickness. The formation mechanism of this layer was investigated systematically through single-track observations and finite-element simulation. Moreover, the increased nanohardness can be attributed to the uniformly dispersed, intimately contacted ceramic nanoparticles in the matrix. The results indicated the multifunctionality of L-PBF-processed metallic parts, introducing the possibility of fabricating advanced ultrahigh-temperature materials.
关键词： carbon nanotubes,metal matrix composites,molybdenum,oxidation resistance,laser powder bed fusion
更新于2025-09-23 15:19:57
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Laser Powder Bed Fusion of high strength aluminum
摘要： Demands for high strength aluminum alloys processed by Laser Powder Bed Fusion (LPBF) are high and keep rising. However, expensive new alloy compositions or crack formation in existing alloys hinder its wide applicability. It is known from recent work that addition of grain refiners leads to a fine grain structure enabling crack-free, high strength aluminum LPBF parts. In this research, 1wt% of Zr was added to Al7050. Furthermore, an excess of Zn was provided in the powder material to compensate for Zn losses during LPBF and to maintain the Mg:Zn ratio required for formation of strong and coherent MgZn2 precipitates. After a solution and aging heat treatment, the newly developed alloy has an ultimate tensile strength of 500MPa and Vickers micro-hardness of 200Hv-0.5kg. Although the elongation at break of the resulting parts is limited, this research shows promising results for future alloy design of affordable high strength aluminum alloys to be processed by LPBF.
关键词： grain refinement,aluminum,Laser Powder Bed Fusion,cracks
更新于2025-09-23 15:19:57
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Axiomatic Design of Test Artifact for Laser Powder Bed Fusion Machine Capability Assessment
摘要： Additive Manufacturing is increasingly growing in importance in the manufacturing environment, allowing to realize very complex product designs. Identifying the real machine capability is becoming fundamental as additive manufacturing technologies are starting to substitute conventional manufacturing processes. This aspect holds particularly true in the case of Laser Powder Bed Fusion technology. In this case, the method to investigate and determine the actual machine capabilities still represents an open point. In this paper, we propose an analysis of a well-known test artifact from an Axiomatic Design standpoint; based on the results and the review of the Customer Needs, we develop an improved design which is able to ensure a robust analysis for a reliable machine performance check.
关键词： Laser Powder Bed Fusion,Machine Capability Assessment,Additive Manufacturing,Axiomatic Design
更新于2025-09-23 15:19:57
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Preparation of Fe-Co-B-Si-Nb bulk metallic glasses by laser powder bed fusion: Microstructure and properties
摘要： In this work, laser powder bed fusion (LPBF) was employed for the preparation of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 bulk metallic glasses (BMGs). Microstructural evolution, thermal stability and mechanical properties of LPBF-processed samples using different laser power and scanning speed were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA), electron backscatter diffraction (EBSD), differential scanning calorimetry (DSC) and nanoindentation. The results show that low area energy input facilitates the formation of Fe-Co-B-Si-Nb BMGs with a large amorphous fraction. LPBF-processed sample with an area energy density of 1.25 J/mm2 (at a laser power of 60 W and a scanning speed of 600 mm/s) exhibits a nearly fully glassy microstructure with an amorphous fraction of approximately 99%, meanwhile identical characteristic properties of LPBF-processed samples are correlated with the processing parameters during LPBF. This work demonstrates that LPBF is a promising method to prepare fully amorphous Fe-Co-B-Si-Nb BMGs. The results provide key insights for the fabrication of BMGs and BMGs composites with the desired microstructure possessing almost and properties by additive manufacturing.
关键词： Bulk metallic glasses,Laser powder bed fusion,Amorphous fraction,Crystallization,Microstructure,Nanoindentation
更新于2025-09-23 15:19:57