Rapid Solidification in Bulk Ti-Nb Alloys by Single-Track Laser Melting

Roehling, John D.; Perron, Aurélien; Fattebert, Jean‐Luc; Haxhimali, Tomorr; Guss, Gabe; Li, Tian T.; Bober, David B.; Stokes, Adam; Clarke, Amy J.; Turchi, P. E. A.; Matthews, Manyalibo J.; McKeown, Joseph T.

doi:10.1007/s11837-018-2920-2

Cited by 33 publications

(12 citation statements)

References 41 publications

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“…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. Roehling et al [8] simulated the solidification microstructure of a binary Ti-Nb alloy during rapid solidification conditions encountered during laser track melting of initially arc-melted beads. The phase field simulations based on the AMPE code allowed direct integration of the alloy thermodynamics with the solidification model.…”

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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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 single-track test is a method used to obtain a melt pool on a line by scanning a laser only on a single line under various fabrication conditions; this test can be performed in a shorter duration compared with fabricating parts of several tens of square millimeters. Keyholing is a phenomenon in which the porosity remains at the bottom of the melt pool when the melt pool has an extremely large depth relative to its width [12,13]. Keyholing occurs under high laser power and low scan speed conditions.…”

Section: Introductionmentioning

confidence: 99%

Process Parameter Optimization Framework for the Selective Laser Melting of Hastelloy X Alloy Considering Defects and Solidification Crack Occurrence

et al. 2021

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Recent years have witnessed increasing demand for selective laser melting (SLM) in practical applications; however, determining the appropriate process parameter range remains challenging. In this study, a framework was developed to determine the appropriate process parameter range considering the occurrence of defects and cracks by conducting a single-track test and thermal elastoplastic analysis. Keyholing, balling, and the residual unmelted regions were considered defects. The occurrence of solidification cracking, which is predominant in the SLM of solution-strengthened Ni-based alloys, was considered. Using the proposed framework, we could fabricate a part with largely no defects or cracks, except for the edges, under the determined optimal process parameters.

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“…In general, the high-temperature thermodynamic information often provides useful guidance for controlling thermally induced phase evolution and/or reaction kinetics of the chemical compounds (e.g., thermal decomposition at high temperatures) [10]. In addition, the temperature-dependent thermodynamics is the important basis for modeling phase transformations and associated microstructure evolution upon temperature variation since it determines the driving force for the kinetic processes [11][12][13]. To this end, accurate computational approaches for investigating the thermodynamics at elevated temperatures can play a critical role in establishing essential thermodynamic databases of chemical compounds.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Uranium Tri-Iodide from Density-Functional Theory

et al. 2020

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Density-functional theory (DFT) is employed to investigate the thermodynamic and ground-state properties of bulk uranium tri-iodide, UI3. The theory is fully relativistic and electron correlations, beyond the DFT and generalized gradient approximation, are addressed with orbital polarization. The electronic structure indicates anti-ferromagnetism, in agreement with neutron diffraction, with band gaps and a non-metallic system. Furthermore, the formation energy, atomic volume, crystal structure, and heat capacity are calculated in reasonable agreement with experiments, whereas for the elastic constants experimental data are unavailable for comparison. The thermodynamical properties are modeled within a quasi-harmonic approximation and the heat capacity and Gibbs free energy as functions of temperature agree with available calculation of phase diagram (CALPHAD) thermodynamic assessment of the experimental data.

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Rapid Solidification in Bulk Ti-Nb Alloys by Single-Track Laser Melting

Cited by 33 publications

References 41 publications

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

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

Process Parameter Optimization Framework for the Selective Laser Melting of Hastelloy X Alloy Considering Defects and Solidification Crack Occurrence

Thermodynamics of Uranium Tri-Iodide from Density-Functional Theory

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