Fabrication of Single Crystals through a µ-Helix Grain Selection Process during Electron Beam Metal Additive Manufacturing

Gotterbarm, Martin R.; Rausch, Alexander M.; Körner, Carolin

doi:10.3390/met10030313

Cited by 50 publications

(27 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The powder particles showed spherical morphology with few satellites and moderate residual porosity (compare Figure 1). As shown in Reference [33], the process parameters led to single crystals (SX). The SX were surrounded by a polycrystalline (PX) shell with a thickness of about 2 mm perpendicular to the build direction.…”

Section: Setupmentioning

confidence: 91%

“…Therefore, the transient concentration gradient in the interdendritic region shrinks, leading to a decrease in constitutional undercooling produced by remelting. This can explain why single crystals can be produced by PBF processes [33,54,55]. With common hatching methods, the cooling rate can be further decreased, and nucleation at the border vanishes.…”

Section: Solidmentioning

confidence: 99%

See 1 more Smart Citation

New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion

et al. 2020

Self Cite

View full text Add to dashboard Cite

A microstructure has significant influence on the mechanical properties of parts. For isotropic properties, the formation of equiaxed microstructures by the nucleation of new grains during solidification is necessary. For conventional solidification processes, nucleation is well-understood. Regarding powder bed fusion, the repeated remelting of previous layers can cause nucleation under some conditions that are not explainable with classical theories. Here, we investigate this nucleation mechanism with an unprecedented level of detail. In the first step, we built samples with single crystalline microstructures from Ni-base superalloy IN718 by selective electron beam melting. In the second step, single lines with different parameters were molten on top of these samples. We observed a huge number of new grains by nucleation at the melt-pool border of these single lines. However, new grains can only prevail if the alignment of their crystallographic orientation with respect to the local temperature gradient is superior to that of the base material. The current hypothesis is that nucleation at the melt-pool border happens due to remelting microsegregations from former solidification processes leading to constitutional undercooling directly at the onset of solidification. This study offers the opportunity to understand and exploit this mechanism for different manufacturing processes.

show abstract

Section: Setupmentioning

confidence: 91%

Section: Solidmentioning

confidence: 99%

New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Process design and engineering and quality assurance are addressed in several contributions [3][4][5].…”

Section: Contributionsmentioning

confidence: 99%

“…The grain structure of parts made using selective electron beam melting (SEBM) can be influenced strongly by the processing parameters. This was studied in [5], where trapezoidal prism samples from IN718 were produced using SEBM with different processing strategies. Based on numerical simulation, the authors demonstrate how technical single crystals develop in IN718 by forcing the temperature gradient along a µ-helix.…”

Section: Contributionsmentioning

confidence: 99%

Metal Additive Manufacturing—State of the Art 2020

Asnafi

2021

Metals

View full text Add to dashboard Cite

show abstract

“…With the development of modern industry, metal-based additive manufacturing has been widely surveyed by international researchers [ 1 , 2 , 3 ]. Different methods of metal-based additive manufacturing have been proposed and studied, such as direct metal laser sintering (DMLS), selective laser melting (SLM), and electron beam melting (EBM).…”

Section: Introductionmentioning

confidence: 99%

Regional Control and Optimization of Heat Input during CMT by Wire Arc Additive Manufacturing: Modeling and Microstructure Effects

2021

View full text Add to dashboard Cite

Wire arc additive manufacturing (WAAM) of aluminum-magnesium (Al–Mg) ER5356 alloy deposits is accomplished by cold metal transfer (CMT). During the process, the temperature change of the alloy deposits has a great influence on molding quality, and the microstructure and properties of alloy deposits are also affected by the complex thermal history of the additive manufacturing process. Here, we used an inter-layer cooling process and controlled the heat input process to attempt to reduce the influence of thermal history on alloy deposits during the additive process. The results showed that inter-layer cooling can optimize the molding quality of alloy deposits, but with the disadvantages of a long test time and slow deposition rate. A simple and uniform reduction of heat input makes the molding quality worse, but controlling the heat input by regions can optimize the molding quality of the alloy deposits. The thermophysical properties of Al-Mg alloy deposits were measured, and we found that the specific heat capacity and thermal diffusivity of alloy deposits were not obviously affected by the temperature. The microstructure and morphology of the deposited specimens were observed and analyzed by microscope and electron back-scatter diffraction (EBSD). The process of controlled heat input results in a higher deposition rate, less side-wall roughness, minimum average grain size, and less coarse recrystallization. In addition, different thermal histories lead to different texture types in the inter-layer cooling process. Finally, a controlled heat input process yields the highest average microhardness of the deposited specimen, and the fluctuation range is small. We expect that the process of controlling heat input by model height region will be widely used in the WAAM field.

show abstract

Fabrication of Single Crystals through a µ-Helix Grain Selection Process during Electron Beam Metal Additive Manufacturing

Cited by 50 publications

References 20 publications

New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion

New Grain Formation by Constitutional Undercooling Due to Remelting of Segregated Microstructures during Powder Bed Fusion

Metal Additive Manufacturing—State of the Art 2020

Regional Control and Optimization of Heat Input during CMT by Wire Arc Additive Manufacturing: Modeling and Microstructure Effects

Contact Info

Product

Resources

About