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Assessment of laser power and scan speed influence on microstructural features and consolidation of AISI H13 tool steel processed by additive manufacturing
摘要： Additive manufacturing can produce parts with complex geometries in fewer steps than conventional processing, which leads to cost reduction and a higher quality of goods. One potential application is the production of molds and dies with conformal cooling for injection molding, die casting, and forging. AISI H13 tool steel is typically used in these applications because of its high hardness at elevated temperatures, high wear resistance, and good toughness. However, available data on the processing of H13 steel by additive manufacturing are still scarce. Thus, this study focused on the processability of H13 tool steel by powder bed fusion and its microstructural characterization. Laser power (97-216 W) and scan speed (300-700 mm/s) were varied, and the consolidation of parts, common defects, solidification structure, microstructure, and hardness were evaluated. Over the range of processing parameters, microstructural features were mostly identical, consisting of a predominantly cellular solidification structure. Cellular/dendritic solidification structure displayed C, Cr, and V segregation toward cell walls. The thermal cycle resulted in alternating layers of heat-affected zones, which varied somewhat in hardness and microstructure. Retained austenite was correlated to the solidification structure and displayed a preferential orientation with {001}//build direction. Density and porosity maps were obtained by helium gas pycnometry and light optical microscopy, respectively, and, along with linear crack density, were used to determine appropriate processing parameters for H13 tool steel. Thermal diffusivity, thermal conductivity, and thermal capacity were measured to determine dimensionless processing parameters, which were then compared to others reported in the literature.
关键词： retained austenite,powder bed fusion,additive manufacturing,conformal cooling,processing parameters
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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3D particle tracking velocimetry for the determination of temporally resolved particle trajectories within laser powder bed fusion of metals
摘要： Within this work, we present a system for the measurement of the three-dimensional (3D) trajectories of spatters and entrained particles during laser powder bed fusion (L-PBF) of metals. It is comprised of two ultrahigh-speed cameras and a reconstruction task specific processing reconstruction algorithm. The system enables an automated determination of 3D measures from the trajectories of a large number of tracked particles. Ambiguity evolving from an underdetermined geometrical situation induced by a two-camera setup is resolved within the tracking using a priori knowledge of L-PBF of metals. All processing steps were optimized to run on a graphics processing unit to allow the processing of large amounts of data within an appropriate time frame. The overall approach was validated by a comparison of the measurement results to synthetic images with a known 3D ground truth.
关键词： laser,high-speed imaging,3D particle velocimetry,image processing,additive manufacturing,powder bed fusion
更新于2025-09-23 15:19:57
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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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A review of metal additive manufacturing technologies: Mechanism of defects formation and simulation of melting and solidification phenomena in laser powder bed fusion process
摘要： In this review, the analysis of melting and solidification phenomena and the mechanism of the occurrence of defects as well as the analysis of melting and solidification using the numerical simulation in laser powder bed fusion (LPBF) process were introduced. In addition, the strategies of suppression of defects were described. The melting and solidification phenomena during LPBF process are relatively similar to those during welding. Since the plume brings about the strong recoil pressure on the melt pool, the keyhole takes place. And when the depth of keyhole becomes more than a threshold, the keyhole pore remains at the bottom of melt pool. Since the plume also brings about spattering and blows out powder, the gas pores are prone to occur easily. The micro-simulation of melting and solidification enables to reproduce the real phenomena. The macro-simulation of melting and solidification phenomena is one of the effective tools to predict the optimum fabrication condition. In order to prevent the occurrence of defects, it is significant not only to obtain the optimum fabrication condition using the process map but also to develop the simulation software. In addition, the use of the monitoring and feedback control system is greatly effective. Therefore the development of the cyber-physical system is needed.
关键词： Numerical simulation,Process parameters,Additive manufacturing,Melting phenomena,Powder bed fusion,Defect,Laser
更新于2025-09-23 15:19:57
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An investigation on the measurement of instantaneous temperatures in laser assisted additive manufacturing by thermal imagers
摘要： Powder bed fusion additive manufacturing processes has started to be investigated by means of temperature distribution and change on parts, since problems such as residual stresses, deformations, microstructural differences and lack of mechanical properties were observed due to temperatures of parts during manufacturing. In the current studies, thermal cameras were used to analyze thermal history of parts. Depending on the accuracy of thermal cameras, temperature values were varied. In this study, a mathematical model which was supported by the data of experimental tests was developed to obtain increased accuracy. Melt pool temperatures were predicted by using the model which consisted of average temperature and extrapolated measurement area approaches. Melt pool temperatures were calculated ranging between 1700 and 2800 °C. Besides, temperature-dependent cooling rate was considered in the model to improve accuracy of temperature measurement. In addition, finite element analysis of manufacturing process was performed to verify results. Comparison between results of the mathematical equations and finite element analysis showed the accuracy as minimum 85% and maximum 98%. A trusted equation was generated to calculate melt pool temperatures by using an ordinary thermal imager.
关键词： Thermal imager,Additive manufacturing,Powder bed fusion,In-situ monitoring
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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[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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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