Thermal characterization of the build chamber in electron beam melting

Landau, E.; Tiferet, Eitan; Ganor, Yaron I.; Ganeriwala, Rishi; Matthews, Manyalibo J.; Braun, Dor; Chonin, Michael; Ziskind, G.

doi:10.1016/j.addma.2020.101535

Cited by 14 publications

(7 citation statements)

References 29 publications

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“…Given that the preheat 1 scan involves the electron beam scanning the bed with a series of parallel lines, it is possible that some of the powder particles which were in the vicinity of the preheat 1 scan lines might have experienced high local temperatures, that were greater than the β-transus temperature and underwent certain level of α′→α+β transformation without reaching the melting point (~1650ºC) [46]. On the other hand, it is likely that the temperature at the away-melt zone region would be lower by ~70ºC of the set preheat temperature [47]. Nevertheless, since the analysed powder particles revealed no significant microstructural transformations (Figure 5) and showed no evidence of β peaks in the XRD plot, it is deduced that the powder particles at the edges of the powder bed were less affected by the EB-PBF processing conditions.…”

Section: Powder Characteristicsmentioning

confidence: 99%

The effects of powder reuse on the mechanical response of electron beam additively manufactured Ti6Al4V parts

Soundarapandiyan

Johnston

Khan

et al. 2021

Additive Manufacturing

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Section: Powder Characteristicsmentioning

confidence: 99%

The effects of powder reuse on the mechanical response of electron beam additively manufactured Ti6Al4V parts

Soundarapandiyan

Johnston

Khan

et al. 2021

Additive Manufacturing

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“…For example, the powder particles previously contained in the hoppers, after the spreading, increase their temperature because of conduction and irradiation phenomena from the substrate. The next phase, preheating, which precedes the melting phase, is designed to achieve gradually an even higher temperature, up to 60-70% of the melting point of the processed material [43][44][45]. Then, thanks to the vacuum environment, the additional heat provided during the subsequent layers preserves a high working temperature over the entire build.…”

Section: Introductionmentioning

confidence: 99%

A phase-field study of neck growth in electron beam powder bed fusion (EB-PBF) process of Ti6Al4V powders under different processing conditions

Rizza

Galati

Iuliano

2022

Int J Adv Manuf Technol

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Traditional sintering processes are carried out to achieve complete material densification. In an electron beam powder bed fusion (EB-PBF) process, the same sintering mechanisms occur but only with the aim to form small connections between the particles (necks). A proper neck formation is central for the EB-PBF process because, among other effects, ensures the thermal stability of the process and helps to avoid smoke phenomena. This work presents a numerical study of neck formation under the EB-PBF processing conditions. A new type of modelling is introduced for the temperature sintering load and included in a phase-field model, which simulates the neck growth during the EB-PBF process of Ti6Al4V powders. The model was validated with an ad-hoc experiment, which provided a deviation with respect to the estimated neck diameter of about 9%. The deviation was investigated by reasonably varying the processing conditions. The results showed that the thermal history, the process time scale (including also the cooling phase), and the geometrical characteristics of the particles significantly affected the sintering rate and neck radius.

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“…The most detailed study on the influence of thermal cycling on Ti-6Al-4 V microstructures was performed on a laser-based, powder-fed AM system with a different thermal history than E-PBF [78]. While some numerical models do exist for E-PBF [79,80], a model incorporating the specific scan strategies and build geometry used here would be required for a complete understanding of the influence of thermal cycles on the microstructural evolution, especially to answer the important question of whether the cycles are sufficient to transform the a' fully or partially back to b. However, some general hypotheses can still be proposed based on the observations in [78] and other literature.…”

Section: Microstructural Evolution During E-pbfmentioning

confidence: 99%

3D characterization of microstructural evolution and variant selection in additively manufactured Ti-6Al-4 V

et al. 2021

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Ti-6Al-4 V is a popular alloy in additive manufacturing (AM) due to its applications in the biomedical implants and aerospace industries where the complex part geometries allowed by AM provide cost and performance benefits. Ti-6Al-4 V goes through a b ? a' transformation after solidification which is known to experience variant selection, e.g., through the formation of clusters of variants which, when situated together, partially accommodate the strain of the phase transformation. During electron beam powder bed fusion AM, an in situ decomposition of a' martensite occurs during the cyclic reheating caused by melting successive layers, resulting in a ? b microstructures. How variant selection influences the evolution beyond the initial rapid cooling remains an open question. Using 3D electron backscatter diffraction, we provide a clearer understanding without ambiguity from sectioning effects of how a' decomposes into microstructures with distinct morphologies and variant/intervariant distributions. We extract quantitative 3D information on the various intervariant boundaries networks formed in samples printed using three different electron beam scanning strategies. This shows that differing mechanisms during the decomposition result in a shift from self-accommodating clusters in an acicular microstructure, to either the preferred growth of six variants in a basketweave microstructure, or to a colony microstructure where variant selection is determined by prior-b grain boundaries. We propose a new representation of the misorientations arising from the Burgers orientation relationship, which we refer to as intervariant network diagram, to reveal how variant selection during the martensitic transformation and subsequent decomposition leads to the intervariant boundary networks observed. This holistic understanding of the microstructural evolution has the potential to allow tailoring of microstructures and properties for specific applications.

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Thermal characterization of the build chamber in electron beam melting

Cited by 14 publications

References 29 publications

The effects of powder reuse on the mechanical response of electron beam additively manufactured Ti6Al4V parts

The effects of powder reuse on the mechanical response of electron beam additively manufactured Ti6Al4V parts

A phase-field study of neck growth in electron beam powder bed fusion (EB-PBF) process of Ti6Al4V powders under different processing conditions

3D characterization of microstructural evolution and variant selection in additively manufactured Ti-6Al-4 V

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