Phase Field Simulation of Dendritic Solidification of Ti-6Al-4V During Additive Manufacturing Process

Wu, Linmin

doi:10.1007/s11837-018-3057-z

Cited by 47 publications

(17 citation statements)

References 47 publications

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“…This agrees with the experimental observation by Yadroitsev et al [41]. Depending on the processing conditions, there are two possible grain structure types commonly found in welded metal [62,[64][65][66][67]. One type is the "competitive grain growth", where the grains at the fusion line may initially be oriented in a favorable direction for growth, but their direction may become unfavorable as the curved solid/liquid interface changes its position.…”

Section: Effect Of Scan Speed On Melt Pool and Microstructuressupporting

confidence: 88%

Modeling of solidification microstructure evolution in laser powder bed fusion fabricated 316L stainless steel using combined computational fluid dynamics and cellular automata

Zhang

2019

Additive Manufacturing

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This work presents a novel modeling framework combining computational fluid dynamics (CFD) and cellular automata (CA), to predict the solidification microstructure evolution of laser powder bed fusion (PBF) fabricated 316L stainless steel. A CA model is developed which is based on the modified decentered square method to improve computational efficiency. Using this framework, the fluid dynamics of the melt pool flow in the laser melting process is found to be mainly driven by the competing Marangoni force and the recoil pressure on the liquid metal surface. Evaporation occurs at the front end of the laser spot. The initial high temperature occurs in the center of the laser spot. However, due to Marangoni force, which drives high-temperature liquid flowing to low-temperature region, the highest temperature region shifts to the front side of the laser spot where evaporation occurs. Additionally, the recoil pressure pushes the liquid metal downward to form a depression zone. The simulated melt pool depths are compared well with the experimental data. Additionally, the simulated solidification microstructure using the CA model is in a good agreement with the experimental observation. The simulations show that

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Section: Effect Of Scan Speed On Melt Pool and Microstructuressupporting

confidence: 88%

Modeling of solidification microstructure evolution in laser powder bed fusion fabricated 316L stainless steel using combined computational fluid dynamics and cellular automata

Zhang

2019

Additive Manufacturing

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“…In a class of AM processes, each layer is built by repeated melting manufacturing have been used as input to simulate the solidification microstructures under directional solidification conditions. Wu and Zhang [7] performed simulations of the solidification microstructure of Ti-6Al-4V alloy assuming it to be a pseudo-binary of Ti with 10% solute for which a linear liquidus slope was specified along with a solidus and liquidus temperature. The 2D simulations showed the formation of a columnar structure after the breakdown of a planar morphology under the given values of G and R. The main disadvantage of the phase field model used was that it was not integrated with the thermodynamics of the ternary alloy.…”

Section: Introductionmentioning

confidence: 99%

Phase Field Simulations of Microstructure Evolution in IN718 Using a Surrogate Ni–Fe–Nb Alloy during Laser Powder Bed Fusion

Radhakrishnan

Gorti

Turner

et al. 2018

Metals

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The solidification microstructure in IN718 during additive manufacturing was modeled using phase field simulations. The novelty of the research includes the use of a surrogate Ni-Fe-Nb alloy that has the same equilibrium solidification range as IN718 as the model system for phase field simulations, the integration of the model alloy thermodynamics with the phase field simulations, and the use of high-performance computing tools to perform the simulations with a high enough spatial resolution for realistically capturing the dendrite morphology and the level of microsegregation seen under additive manufacturing conditions. Heat transfer and fluid flow models were used to compute the steady state temperature gradient and an average value of the solid-liquid (s-l) interface velocity that were used as input for the phase field simulations. The simulations show that the solidification morphology is sensitive to the spacing between the columnar structures. Spacing narrower than a critical value results in continued growth of a columnar microstructure, while above a critical value the columnar structure evolves into a columnar dendritic structure through the formation of secondary arms. These results are discussed in terms of the existing columnar to dendritic transition (CDT) theories. The measured interdendritic Nb concentration, the primary and secondary arm spacing is in reasonable agreement with experimental measurements performed on the nickel-base superalloy IN718. and solidification of a powder bed using moving heat sources based on electron beam or laser. Part of the previously solidified layer is re-melted during a subsequent pass. The solidification microstructure that develops during the process is influenced both by the thermal history as well as the underlying structure in the previously solidified layer. The characteristics of the solidification microstructure including primary and secondary dendrite arms spacing, solute distribution within the dendrites and the dendrite orientations have a direct bearing on the mechanical properties of the as-processed component. Also, during post-processing heat treatment, evolution of the microstructure depends on the primary solidification structure due to potential solid-state transformations. Therefore, it is important to quantitatively predict the solidification microstructure in a given alloy, under a given set of processing parameters. An excellent review of the processing-structure relationships during AM of structural alloys is available in a recent publication [1].A key feature of the powder bed fusion processes is the extremely high cooling rate experienced by the melt pool. Typical cooling rates are of the order of 10 6 K/s. Under extreme conditions, the velocity of the solid-liquid (s-l) interface can approach several meters per second, especially along the heat source travel direction. This could cause significant deviation from thermodynamic equilibrium at the moving s-l interface. Non-equilibrium solute-partitioning could lead to a reduction in the solute...

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“…The interface thickness is 5 units. Referring to the research of Gong et al [18][19][20], some physical parameters are obtained, as shown in Table 1. Table 1.…”

Section: Model Of Phase Fieldmentioning

confidence: 99%

“…Yang et al's research [13][14][15][16][17] concentrated on the finite element model for additive manufacturing, and the temperature field distribution of the additive manufacturing process was obtained, while macroscopic temperature field data were not introduced into the microstructure simulation, and there was a lack of description of the phase transition process. Gong et al [18][19][20] studied the microstructure evolution of EBAM Ti-6Al-4V during solidification, while the microstructure simulation of Ti-6Al-4V processed by SLM was unattended. Through the combination of macroscopic finite element simulation and microscopic phase field simulation, this paper attempts to bring the influence of macroscopic parameters into the microstructure.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Ti-6Al-4V Microstructure Evolution in Selective Laser Melting

Ding

Sun

Liang

et al. 2019

Metals

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Selective laser melting (SLM) is an advanced additive manufacturing technique that can produce complex and accurate metal samples. Since the process performs local high heat input during a very short interaction time, the physical parameters in the solidification are difficult to measure experimentally. In this work, the microstructure evolution of Ti-6Al-4V alloy in additive manufacturing was studied. With the increase of scanning speed, the cooling rate and the temperature gradient of molten pool position increased, which was attributed to the gradual decrease of energy density. The phase-field simulation resulted in the overall microstructure morphology of columnar crystals owing to the very large temperature gradient and cooling rate obtained from the temperature field. Microsegregation was observed during dendritic formation, and the solute was enriched in the liquid phase near the dendritic tip and between the dendritic arms due to the lower equilibrium distribution coefficient. The scanning speed had an effect on the dendrite spacing.

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Phase Field Simulation of Dendritic Solidification of Ti-6Al-4V During Additive Manufacturing Process

Cited by 47 publications

References 47 publications

Modeling of solidification microstructure evolution in laser powder bed fusion fabricated 316L stainless steel using combined computational fluid dynamics and cellular automata

Modeling of solidification microstructure evolution in laser powder bed fusion fabricated 316L stainless steel using combined computational fluid dynamics and cellular automata

Phase Field Simulations of Microstructure Evolution in IN718 Using a Surrogate Ni–Fe–Nb Alloy during Laser Powder Bed Fusion

Investigation on Ti-6Al-4V Microstructure Evolution in Selective Laser Melting

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