Prediction of microstructure in laser powder bed fusion process

Acharya, Ranadip; Sharon, John Anthony; Staroselsky, Alexander

doi:10.1016/j.actamat.2016.11.018

Cited by 239 publications

(79 citation statements)

References 25 publications

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“…The reasons are explained below: a large temperature gradient accompanied by temperature fluctuation in the exposed molten pool, which causes the density differences of fluids. The high‐temperature fluids with a low density inevitably rose; on the contrary, the low‐temperature fluids with a high density sank, which leads to convection of fluids in the molten pool . The heat flow remelts the previously formed columnar crystals and triggers them to peel off .…”

Section: Resultsmentioning

confidence: 99%

“…The high-temperature fluids with a low density inevitably rose; www.advancedsciencenews.com www.aem-journal.com on the contrary, the low-temperature fluids with a high density sank, which leads to convection of fluids in the molten pool. [33,34] The heat flow remelts the previously formed columnar crystals and triggers them to peel off. [23,35] The detached grains are engulfed into the molten pool and formed free grains, which may become the source of crystal nuclei in fine-grain zone (FGZ).…”

Section: Remelting Strategymentioning

confidence: 99%

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Selective Laser Melting and Remelting of Pure Tungsten

et al. 2020

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The processing of pure tungsten encounters a substantial challenge due to its high melting point and intrinsic brittleness. Selective laser melting (SLM) technique is gaining popularity and offers an excellent processing approach for refractory metals. Herein, dense pure tungsten specimens are produced by optimizing SLM processing parameters. The mechanical property of the SLM‐produced tungsten with an ultimate compressive strength of about 1200 MPa, which is obviously superior to that reported in other literature, is achieved. The increased laser energy input is instrumental in raising density and surface roughness of tungsten specimens. Interestingly, additional remelting of processed layers during SLM improves the surface quality and the microstructure and achieves the highest relative density (98.4% ± 0.5%). After laser remelting, the surface roughness is reduced by 28% and a large number of fine grains are obtained. The flow of fluids caused by remelting plays a decisive role in the formation of fine grains and the defect level. Therefore, these findings offer a new insight into SLM of pure tungsten.

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Section: Resultsmentioning

confidence: 99%

Section: Remelting Strategymentioning

confidence: 99%

Selective Laser Melting and Remelting of Pure Tungsten

et al. 2020

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“…MICRESS is based on the multiphase-field approach. [9,10] The multiphase-field theory describes the evolution of multiple phase-field parameters / a¼1;2;...;v ¼ ðx; tÞ (with the constraint P v a¼1 / a ¼ 1) in space and time, which represent the spatial distribution of multiple phases with different thermodynamic properties and/or multiple grains with different orientations. The phase-field parameter, / a takes a value of 1 if phase a is present locally and a value of 0 if the phase is not present locally.…”

Section: A Micress and The Governing Equationmentioning

confidence: 99%

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Kumara

Deng

Hanning

et al. 2019

Metall Mater Trans A

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Electron beam melting (EBM) is a powder bed additive manufacturing process where a powder material is melted selectively in a layer-by-layer approach using an electron beam. EBM has some unique features during the manufacture of components with high-performance superalloys that are commonly used in gas turbines such as Alloy 718. EBM has a high deposition rate due to its high beam energy and speed, comparatively low residual stresses, and limited problems with oxidation. However, due to the layer-by-layer melting approach and high powder bed temperature, the as-built EBM Alloy 718 exhibits a microstructural gradient starting from the top of the sample. In this study, we conducted modeling to obtain a deeper understanding of microstructural development during EBM and the homogenization that occurs during manufacturing with Alloy 718. A multicomponent phase-field modeling approach was combined with transformation kinetic modeling to predict the microstructural gradient and the results were compared with experimental observations. In particular, we investigated the segregation of elements during solidification and the subsequent ''in situ'' homogenization heat treatment at the elevated powder bed temperature. The predicted elemental composition was then used for thermodynamic modeling to predict the changes in the continuous cooling transformation and time-temperature transformation diagrams for Alloy 718, which helped to explain the observed phase evolution within the microstructure. The results indicate that the proposed approach can be employed as a valuable tool for understanding processes and for process development, including post-heat treatments.

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“…The simulations of melt pool solidification in Ref. [36] are particularly interesting where an initial solid-liquid interface, similar to the resolidification boundary in our Fig. 3, resulted in local nucleation and growth of multiple dendrites with a misorientation with the vertical direction between 0 • to 20 • depending on the scan velocity, thermal gradient, interface roughness and initial seed position.…”

Section: Discussionmentioning

confidence: 52%

Single-Track Melt-Pool Measurements and Microstructures in Inconel 625

Ghosh

Levine

et al. 2018

JOM

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We use single track laser melting experiments and simulations on Inconel 625 to estimate the dimensions and microstructures of the resulting melt pools. Our work is based on a design-of-experiments approach which uses multiple laser power and scan speed combinations. Single track experiments generate melt pools of certain dimensions. These dimensions reasonably agree with our finite element calculations. Phase-field simulations predict the size and segregation of the cellular microstructures that form along the melt pool boundaries for the solidification conditions that change as a function of melt pool dimensions.

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Prediction of microstructure in laser powder bed fusion process

Cited by 239 publications

References 25 publications

Selective Laser Melting and Remelting of Pure Tungsten

Selective Laser Melting and Remelting of Pure Tungsten

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Single-Track Melt-Pool Measurements and Microstructures in Inconel 625

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