Real time monitoring of electron emissions during electron beam powder bed fusion for arbitrary geometries and toolpaths

Ledford, Christopher; Tung, Mouda; Rock, Chris; Horn, Timothy

doi:10.1016/j.addma.2020.101365

Cited by 14 publications

(12 citation statements)

References 38 publications

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“…The work by Guschlbauer et al also highlights, in a more systematic way than previous studies, the influence of copper oxides on the strength and ductility in as-fabricated conditions. However, the processing space reported by Ledford et al [ 1 , 26 ] is in contrast with others as the substrate temperature is relatively low because of the low initial oxygen content of the powder that tends to sinter more easily at high temperature preheat settings. Moreover, in literature it is generally seen that oxygen content in the powder feedstock ranges from 40 wt.…”

Section: Resultsmentioning

confidence: 96%

“…Lykov et al [ 9 ] reported a UTS of 149 MPa with a relative density of 88.1%, whereas Yan et al [ 10 ] and Jadhav et al [ 14 ] fabricated copper with a relative density up to 99.1% and 99.3% that resulted in an UTS of 248 and 211 MPa, respectively. For EB-PBF, however, most of the reported relative densities exceeded 99.5% [ 11 , 12 , 26 , 27 , 28 ]. Guschlbauer et al reported a maximum UTS of 231.6 MPa tested transverse to the build direction; the lowest UTS reported in the same study was 181.3 MPa oriented parallel to the build direction [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…ppm, beyond which it led to a significant loss of ductility [ 29 ], in accord with the findings of Guschlbauer et al [ 11 ] that attributed copper oxides acting as stress concentration sites during the tensile test of EB-PBF processed copper. Further, with the exception of the data presented by Ledford et al [ 1 , 26 ], which do not include any mechanical properties, the EB-PBF automatic control parameters were explicitly disabled. While open-loop on most EB-PBF systems, such parameters serve to regulate beam speed and power to maintain stable melt pool size and powder bed temperature as part geometries evolve.…”

Section: Introductionmentioning

confidence: 99%

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Quasi-Static Tensile Properties of Unalloyed Copper Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

2021

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Mechanical properties of powder bed fusion processed unalloyed copper are reported majorly in the as-fabricated condition, and the effect of post-processes, common to additive manufacturing, is not well documented. In this study, mechanical properties of unalloyed copper processed by electron beam powder bed fusion are characterized via room temperature quasi-static uniaxial tensile test and Vickers microhardness. Tensile samples were extracted both perpendicular and parallel to the build direction and assigned to three different conditions: as-fabricated, hot isostatic pressing (HIP), and vacuum annealing. In the as-fabricated condition, the highest UTS and lowest elongation were obtained in the samples oriented perpendicular to the build direction. These were observed to have clear trends between sample orientation caused primarily by the interdependencies between the epitaxial columnar grain morphology and dislocation movement during the tensile test. Texture was insignificant in the as-fabricated condition, and its effect on the mechanical properties was outweighed by the orientation anisotropy. The fractographs revealed a ductile mode of failure with varying dimple sizes where more shallow and finely spaced dimples were observed in the samples oriented perpendicular to the build direction. EDS maps reveal that grain boundary oxides coalesce and grow in HIP and vacuum-annealed specimens which are seen inside the ductile dimples and contribute to their increased ductility. Overall, for the post-process parameters chosen in this study, HIP was observed to slightly increase the sample’s density while vacuum annealing reduced the oxygen content in the specimens.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quasi-Static Tensile Properties of Unalloyed Copper Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

2021

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“…All samples were fabricated using a customized Arcam S12 EB-PBF machine (GE Additive, Cincinnati, OH, USA) (software version 3.2). As described in our previous work [ 32 , 33 ] the build platform was modified to contain a reduced size (88 mm diameter × 35 mm) CP Ti substrate. Process monitoring was performed with standard machine thermocouples (type K) located below the build plate, a 2-color pyrometer (Fluke Process Endurance Pyrometer) focused on the center of the powder bed, and an IR camera (FLIR A655sc, Wilsonville, OR, USA) mounted on an observation port on the top of the build chamber.…”

Section: Methodsmentioning

confidence: 99%

Electron Beam Melting of Niobium Alloys from Blended Powders

et al. 2021

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Niobium-based tungsten alloys are desirable for high-temperature structural applications yet are restricted in practice by limited room-temperature ductility and fabricability. Powder bed fusion additive manufacturing is one technology that could be leveraged to process alloys with limited ductility, without the need for pre-alloying. A custom electron beam powder bed fusion machine was used to demonstrate the processability of blended Nb-1Zr, Nb-10W-1Zr-0.1C, and Nb-20W-1Zr-0.1C powders, with resulting solid optical densities of 99+%. Ultimately, post-processing heat treatments were required to increase tungsten diffusion in niobium, as well as to attain satisfactory mechanical properties.

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“…Details of the system capabilities are described elsewhere. [19][20][21] Six cylindrical specimens measuring 12 mm in diameter by 13 mm tall were fabricated with software version 3.2 SP2. The composition of the samples was varied in three distinct regions as illustrated in Fig.…”

Section: Sample Fabricationmentioning

confidence: 99%

Additive Manufacturing of Pure Mo and Mo + TiC MMC Alloy by Electron Beam Powder Bed Fusion

Rock¹,

Ellis²,

Ledford³

et al. 2020

JOM

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A metal matrix composite powder of molybdenum (Mo) + TiC was produced by mechanical alloying (MA) and used in additive manufacturing by electron beam powder bed fusion along with pure Mo powder to form sandwich structures. The Mo + TiC solid layers formed mixed structures of Mo with discrete TiC particles, eutectic Mo + TiC, and Mo dendrites. Thermodynamic modeling showed that the system contained an invariant eutectic reaction in the composition range used and indicated that the system was highly sensitive to changes in composition and temperature.

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Real time monitoring of electron emissions during electron beam powder bed fusion for arbitrary geometries and toolpaths

Cited by 14 publications

References 38 publications

Quasi-Static Tensile Properties of Unalloyed Copper Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

Quasi-Static Tensile Properties of Unalloyed Copper Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

Electron Beam Melting of Niobium Alloys from Blended Powders

Additive Manufacturing of Pure Mo and Mo + TiC MMC Alloy by Electron Beam Powder Bed Fusion

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