Electron beam additive manufacturing of Ti6Al4V: Evolution of powder morphology and part microstructure with powder reuse

Ghods, S.; Schultz, E.; Wisdom, C.; Schur, R.; Pahuja, Rishi; Montelione, A.; Arola, D.; Ramulu, M.

doi:10.1016/j.mtla.2020.100631

Cited by 62 publications

(31 citation statements)

References 41 publications

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“…The analysis of the shape of the particles of both powders showed that, as presented in Figure 1 b, a small shift in the sphericity factor towards higher values may be noticed in USED powder. This may indicate accumulation of spherical by-products of laser–powder interaction (e.g., spatters) [ 17 , 38 ].…”

Section: Resultsmentioning

confidence: 99%

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Reuse of Ti6Al4V Powder and Its Impact on Surface Tension, Melt Pool Behavior and Mechanical Properties of Additively Manufactured Components

et al. 2021

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The quality and characteristics of a powder in powder bed fusion processes play a vital role in the quality of additively manufactured components. Its characteristics may influence the process in various ways. This paper presents an investigation highlighting the influence of powder deterioration on the stability of a molten pool in a laser beam powder bed fusion (LB-PBF, selective laser melting) process and its consequences to the physical properties of the alloy, porosity of 3D-printed components and their mechanical properties. The intention in this was to understand powder reuse as a factor playing a role in the formation of porosity in 3D-printed components. Ti6Al4V (15 μm–45 μm) was used as a base material in the form of a fresh powder and a degraded one (reused 12 times). Alloy degradation is described by possible changes in the shape of particles, particle size distribution, chemical composition, surface tension, density and viscosity of the melt. An approach of 3D printing singular lines was applied in order to study the behavior of a molten pool at varying powder bed depths. Single-track cross-sections (STCSs) were described with shape parameters and compared. Furthermore, the influence of the molten pool stability on the final density and mechanical properties of a material was discussed. Electromagnetic levitation (EML) was used to measure surface tension and the density of the melt using pieces of printed samples. It was found that the powder degradation influences the mechanical properties of a printed material by destabilizing the pool of molten metal during printing operation by facilitating the axial flow on the melt along the melt track axis. Additionally, the observed axial flow was found to facilitate a localized lack of fusion between concurrent layers. It was also found that the surface tension and density of the melt are only impacted marginally or not at all by increased oxygen content, yet a difference in the temperature dependence of the surface tension was observed.

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Section: Resultsmentioning

confidence: 99%

“…The performed annealing process was aimed at relieving stresses rather than to decompose martensite. According to Ghods et al [ 38 ], the chemical changes observed in the USED powder would require a greater increase in the oxygen content in order to have a noticeable impact on the microstructure of a 3D-printed Ti6Al4V.…”

Section: Resultsmentioning

confidence: 99%

Reuse of Ti6Al4V Powder and Its Impact on Surface Tension, Melt Pool Behavior and Mechanical Properties of Additively Manufactured Components

et al. 2021

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“…In this process, the thermal stress generated cannot be released in time, exceeding the bearing limit of the material, resulting in the formation of thermal cracks, as shown in Figure 6a. Guschlbauer et al [12] reported crack defects in forming copper alloys, and Chauvet et al [13] also reported crack defects in forming nickel-based superalloys. When the electron beam acted on the powder, the powders with smaller sizes are melted first because of the rather smaller energy required.…”

Section: Defects Of Electron Beam Melting Of Ti-6al-4v Alloymentioning

confidence: 99%

“…Razavi et al [2] reported that equiaxed α grains were observed in the evaluated Ti-6Al-4V samples. Columnar prior β-grains were found to grow through multiple layers and their major axis oriented along the build direction for EBM parts [2,13,14].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Electron Beam Melting

et al. 2020

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Electron beam melting technique is a kind of near-net shaping, environmentally friendly metal additive manufacturing technique, which can form high-performance metal parts with complex shapes. It has been widely applied in the aerospace industry, biomedical application, automobile manufacturing, and other fields. Ti-6Al-4V is the most widely researched and applied alloy in the additive manufacturing field, but its microstructure is diverse, and its mechanical properties vary greatly. In this study, the effect of process parameters on the microstructure and the resulting mechanical properties of Ti-6Al-4V alloy was researched. The results show that the yield strength of Ti-6Al-4V alloy with a bimodal microstructure is higher than those with a basketweave microstructure. Energy dispersion spectrum (EDS) line scan and area scan results show that there is no element enrichment for the specimens with the highest yield strength. A speed factor of less than 40 is a must for obtaining relatively dense Ti-6Al-4V parts built with electron beam melting. We have done basic research for the subsequent manufacturing of complex shape parts, which is helpful to promote the application of electron beam melting technology in the aerospace field.

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“…Oxygen stabilizes the α-Ti phase which pins dislocation during part deformation. Thus, with powder reuse, ultimate yield strength slightly increases, while ductility decreases [ 18 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

Topological, Mechanical and Biological Properties of Ti6Al4V Scaffolds for Bone Tissue Regeneration Fabricated with Reused Powders via Electron Beam Melting

et al. 2021

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Cellularized scaffold is emerging as the preferred solution for tissue regeneration and restoration of damaged functionalities. However, the high cost of preclinical studies creates a gap between investigation and the device market for the biomedical industry. In this work, bone-tailored scaffolds based on the Ti6Al4V alloy manufactured by electron beam melting (EBM) technology with reused powder were investigated, aiming to overcome issues connected to the high cost of preclinical studies. Two different elementary unit cell scaffold geometries, namely diamond (DO) and rhombic dodecahedron (RD), were adopted, while surface functionalization was performed by coating scaffolds with single layers of polycaprolactone (PCL) or with mixture of polycaprolactone and 20 wt.% hydroxyapatite (PCL/HA). The mechanical and biological performances of the produced scaffolds were investigated, and the results were compared to software simulation and experimental evidence available in literature. Good mechanical properties and a favorable environment for cell growth were obtained for all combinations of scaffold geometry and surface functionalization. In conclusion, powder recycling provides a viable practice for the biomedical industry to strongly reduce preclinical costs without altering biomechanical performance.

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Electron beam additive manufacturing of Ti6Al4V: Evolution of powder morphology and part microstructure with powder reuse

Cited by 62 publications

References 41 publications

Reuse of Ti6Al4V Powder and Its Impact on Surface Tension, Melt Pool Behavior and Mechanical Properties of Additively Manufactured Components

Reuse of Ti6Al4V Powder and Its Impact on Surface Tension, Melt Pool Behavior and Mechanical Properties of Additively Manufactured Components

Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Electron Beam Melting

Topological, Mechanical and Biological Properties of Ti6Al4V Scaffolds for Bone Tissue Regeneration Fabricated with Reused Powders via Electron Beam Melting

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