scholarly journals Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7240
Author(s):  
Christopher Arnold ◽  
Christoph Breuning ◽  
Carolin Körner
Keyword(s):  
Electron Beam ◽  
Thermodynamic Simulation ◽  
Dimensional Accuracy ◽  
Powder Bed Fusion ◽  
Process Data ◽  
Powder Bed ◽  
Post Process ◽  
X Ray Computed ◽  
In Situ Imaging

The current study evaluates the capabilities of electron-optical (ELO) in situ imaging with respect to monitoring and prediction of manufacturing precision in electron beam powder bed fusion. Post-process X-ray computed tomography of two different as-built parts is used to quantitatively evaluate the accuracy and limitations of ELO imaging. Additionally, a thermodynamic simulation is performed to improve the understanding of ELO data and to assess the feasibility of predicting dimensional accuracy numerically. It is demonstrated that ELO imaging captures the molten layers accurately (deviations <100 μm) and indicates the creation of surface roughness. However, some geometrical features of the as-built parts exhibit local inaccuracies associated with thermal stress-induced deformation (deviations up to 500 μm) which cannot be captured by ELO imaging. It is shown that the comparison between in situ and post-process data enables a quantification of these effects which might provide the possibility for developing effective countermeasures in the future.

Fundamental Requirements for Data Representations in Laser-Based Powder Bed Fusion

2015 ◽  
Author(s):  
Shaw C. Feng ◽  
Paul W. Witherell ◽  
Gaurav Ameta ◽  
Duck Bong Kim
Keyword(s):  
Additive Manufacturing ◽  
Heterogeneous Systems ◽  
Powder Bed Fusion ◽  
Process Data ◽  
Data Interoperability ◽  
Powder Bed ◽  
Related Data ◽  
Data Representations ◽  
Am Processes

Additive Manufacturing (AM) processes intertwine aspects of many different engineering-related disciplines, such as material metrology, design, in-situ and off-line measurements, and controls. Due to the increasing complexity of AM systems and processes, data cannot be shared among heterogeneous systems because of a lack of a common vocabulary and data interoperability methods. This paper aims to address insufficiencies in laser-based Powder Bed Fusion (PBF), a specific AM process, data representations to improve data management and reuse in PBF. Our approach is to formally decompose the processes and align PBF process-specifics with information elements as fundamental requirements for representing process-related data. The paper defines the organization and flow of process information. After modeling selected PBF processes and sub-processes as activities, we discuss requirements for the development of more advanced process data models that provide common terminology and process knowledge for managing data from various stages in AM.

scholarly journals In Situ CT Tensile Testing of an Additively Manufactured and Heat-Treated Metastable ß-Titanium Alloy (Ti-5Al-5Mo-5V-3Cr)

2021 ◽  
Vol 11 (21) ◽  
pp. 9875
Author(s):  
Julius Hendl ◽  
Sina Daubner ◽  
Axel Marquardt ◽  
Lukas Stepien ◽  
Elena Lopez ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Beam ◽  
Tensile Testing ◽  
Fusion Process ◽  
Fracture Mechanisms ◽  
Powder Bed Fusion ◽  
Complex Load ◽  
Powder Bed ◽  
Heat Treated

Additive manufacturing has been considered a suitable process for developing high-performance parts of medical or aerospace industries. The electron beam powder bed fusion process, EB‑PBF, is a powder bed fusion process carried out in a vacuum, in which the parts are melted using a highly focused electron beam. The material class of metastable β‑titanium alloys, and especially Ti‑5Al‑5Mo‑5V‑3Cr, show great potential for use as small and highly complex load-bearing parts. Specimens were additively manufactured with optimised process parameters and different heat treatments used in order to create tailored mechanical properties. These heat-treated specimens were analysed with regard to their microstructure (SEM) and their mechanical strength (tensile testing). Furthermore, in situ tensile tests, using a Deben CT5000 and a YXLON ff35 industrial µ‑CT, were performed and failure‑critical defects were detected, analysed and monitored. Experimental results indicate that, if EB‑PBF-manufactured Ti‑5553 is heat-treated differently, a variety of mechanical properties are possible. Regarding their fracture mechanisms, failure-critical defects can be detected at different stages of the tensile test and defect growth behaviour can be analysed.

scholarly journals In-situ layerwise monitoring of electron beam powder bed fusion using near-infrared imaging

2021 ◽  
Vol 38 ◽  
pp. 101767
Author(s):  
Guillaume Croset ◽  
Guilhem Martin ◽  
Charles Josserond ◽  
Pierre Lhuissier ◽  
Jean-Jacques Blandin ◽  
...  
Keyword(s):  
Electron Beam ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Powder Bed Fusion ◽  
Near Infrared Imaging ◽  
Powder Bed

Influence of Intrinsic Heat Treatment (IHT) on Precipitation Kinetics during Laser Beam Powder Bed Fusion of Al-Mg-Sc Alloy

2021 ◽  
Vol 1161 ◽  
pp. 47-55
Author(s):  
Yuvaraj Ganpati Patil ◽  
Loreen Mertens ◽  
Andre Dröse ◽  
Vasily Ploshikhin
Keyword(s):  
Laser Beam ◽  
Volume Fraction ◽  
Rapid Heating ◽  
Process Analysis ◽  
Powder Bed Fusion ◽  
Precipitation Kinetics ◽  
Powder Bed ◽  
Post Process ◽  
Heating And Cooling

Laser Beam Powder Bed Fusion (LBPBF) process has a unique feature termed as IntrinsicHeat Treatment (IHT), where solidified layers undergo series of heating and cooling (during thesubsequent building of a part). Thus, the LBPBF process offers the opportunity for the formation of microstructuralfeatures, which can have the potential to transform the mechanical properties of the part.In the case of AlMgSc alloy, L12 phase Al3Sc precipitates are thermodynamically favored to nucleatein the Al matrix due to coherency. After post-process analysis, it is evident that Al3Sc precipitatesformed during the LBPBF process, but it is unlikely to monitor (in-situ) the kinetics of precipitation.Therefore, based on inputs from the thermal model, the simulation of precipitation kinetics during theLBPBF process (IHT) is performed. The rapid heating and cooling cause the formation of new vacancies,where Al3Sc precipitates can nucleate and grow. The KWN model based on solid-state phasetransformation is used for modeling of precipitation kinetics. The thermal data at two locations in apart is collected and used to determine the average radius, number density, and volume fraction ofprecipitates. It is found that the IHT does not influence precipitation kinetics, and has no potential toalter the spatial properties of the part.

scholarly journals In Situ Monitoring of Powder Bed Fusion Homogeneity in Electron Beam Melting

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7015
Author(s):  
Marco Grasso
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Infrared Imaging ◽  
Melting Process ◽  
In Situ Monitoring ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
In Situ Sensing ◽  
In Situ Detection

Increasing attention has been devoted in recent years to in situ sensing and monitoring of the electron beam melting process, ranging from seminal methods based on infrared imaging to novel methods based on backscattered electron detection. However, the range of available in situ monitoring capabilities and solutions is still quite limited compared to the wide number of studies and industrial toolkits in laser-based additive manufacturing processes. Some methods that are already industrially available in laser powder bed fusion systems, such as in situ detection of recoating errors, have not yet been investigated and tested in electron beam melting. Motivated by the attempt to fill this gap, we present a novel in situ monitoring methodology that can be easily implemented in industrial electron beam melting machines. The method is aimed at identifying local inhomogeneity and irregularities in the powder bed by means of layerwise image acquisition and processing, with no external illumination source apart from the light emitted by the hot material underneath the currently recoated layer. The results show that the proposed approach is suitable to detect powder bed anomalies, while also highlighting the link between the severity of in situ detected errors and the severity of resulting defects in the additively manufactured part.

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