Simulation of Precipitation Kinetics with Non-Spherical Particles

Wu, Kaisheng; Chen, Qing; Mason, Paul

doi:10.1007/s11669-018-0644-1

Cited by 22 publications

(8 citation statements)

References 25 publications

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“…It should also be noted that the model assumption of spherical precipitates disagree with the experimentally observed elongated precipitates initially. The elongated particles should have faster kinetic evolution due to a larger Gibbs-Thomson effect and a shape effect [47,48]. The elongated precipitates should be considered in further work.…”

Section: Discussion On Improved Modeling Of M 3 C Precipitationmentioning

confidence: 99%

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

et al. 2019

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The precipitation of cementite (M 3 C) from as-quenched martensite during tempering at 500 and 700°C was investigated in a Fe-1C-1Cr (wt%) alloy. Tempering for a short duration at 700°C results in a Cr/Fe ratio in the core region of M 3 C precipitates which is equal to the bulk alloy composition, while a shell on the surface of the precipitates exhibits a higher Cr concentration. With a prolonged tempering up to 5 h, the shell concentration gradually increases toward the equilibrium value, but the core region has not yet reached the equilibrium value. After tempering for 5 s at 500°C, there is no Cr enrichment found at the M 3 C-matrix interface, while a transition to partitioning of Cr is found during the first 5 min of tempering at 500°C. These experimental results indicate that M 3 C grows without significant partitioning of substitutional elements at both temperatures initially, i.e., growth is carbon diffusion controlled. This stage is, however, very short, and soon after 5 s at 700°C and 5 min at 500°C, Cr diffusion becomes important. Calculations using the diffusion simulation software DICTRA and precipitation simulation software TC-PRISMA were performed. The diffusion simulations using the local equilibrium interface condition show excellent agreement with experiments concerning Cr enrichment of the particles, but the size evolution is overestimated. On the other hand, the precipitation simulations underestimate the size evolution. It is suggested that a major improvement in the precipitation model could be achieved by implementing a modified nucleation model that considers nucleation far from the equilibrium composition.

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Section: Discussion On Improved Modeling Of M 3 C Precipitationmentioning

confidence: 99%

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

et al. 2019

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“…The most recent releases of TC-PRISMA [since the 2017b version] have implemented new capabilities to handle precipitates in the shapes of cuboids, needles, and plates. [47] Once the program has additional input data of elastic properties of the precipitate and matrix phases as well as the transformation strains, it minimizes the sum of contributions from both the interfacial energy and the elastic strain energy, and outputs the time-dependent cuboid factor or the aspect ratio that describes the morphological evolution of non-spherical particles. Simulations of non-spherical shapes are a welcoming recent development [48][49][50] that will expand the KWN modeling capabilities to a lot more engineering alloys such as Al alloys and Mg alloys with non-spherical precipitates.…”

Section: Opportunity To Collect Large Datasets On Phase Transformamentioning

confidence: 99%

High-Throughput and Systematic Study of Phase Transformations and Metastability Using Dual-Anneal Diffusion Multiples

Zhao

2020

Metall Mater Trans A

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This article highlights the capabilities of dual-anneal diffusion multiples (DADMs) in performing high-throughput and systematic studies of phase transformations and metastability. DADMs create wide ranges of solid solution compositions through elemental interdiffusion during a first anneal at a high temperature. After quenching to ambient temperature, each diffusion multiple can be cut into several slices, and each slice is further annealed individually at a lower/second temperature. Phase transformations take place in the supersaturated regions of the solid solution compositions that are formed during the first anneal, leading to various precipitates due to different driving force, interfacial energy, and other factors as composition varies across the regions in the sample. By subjecting the sliced diffusion multiples individually to different anneal durations and different second anneal temperatures, very large datasets can be collected on phase transformation kinetics and evolution of precipitate morphology as a function of composition, time, and temperature. Metastable phases and their transitions to more stable phases have been systematically observed in the Fe-Cr-Mo ternary system across a wide range of composition, temperature, and anneal time, thus providing a large amount of information on metastability of the phases. The solvi of the metastable and stable phases can be systematically collected for more reliable CALPHAD assessments of the Gibbs free energy of the metastable phases. By adjusting the interfacial energy value in simulations using models such as the Kampmann-Wagner Numerical (KWN) model and matching the simulated precipitate sizes at different compositions with experimentally measured sizes of the corresponding compositions in a DADM, the interfacial energy value can be obtained. Opportunities and challenges in using DADMs to collect large datasets on precipitation kinetics and morphology will be explained to enable full utilization of the capabilities of DADMs in the future. This review not only presents experimental results collected to date, but also explains the vast more datasets that can be collected from DADMs in the future. An approach that iteratively and holistically integrates experimental results with model predictions is advocated as a very effective means to advance the understanding of various phase transformation mechanisms. In this way, the new mechanistic understanding can be integrated to more robust models to simulate the ''abnormal'' behaviors that are observed in DADMs, especially related to sequential precipitations of phases that are common in engineering alloys. Examples are also shown to illustrate the systematic nature of DADMs as a result of their continuously varying composition regions in catching unusual phenomena and emergent trends that are easily missed during studies using discrete compositions afforded by individual alloys.

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“…The commercially available CALPHAD software package, Thermo-Calc, has an implementation of Langer Schwartz precipitation modeling that uses Kampmann and Wagner numerical methods [5,6]. While thermodynamic and kinetic data can be obtained from CALPHAD databases, interfacial energies between the bulk and precipitate phases are also needed and are mostly not available.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Interfacial Energy for Langer-Schwartz Based Precipitation Simulations

Sarich

Hope²,

Rule³

2021

Heat Treat 2021: Extended Abstracts From the 31st Heat Treating Society Conference and Exposition

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Precipitation kinetics were investigated in select Fe, Ni, and Al alloys using a CALPHAD based precipitation model based on Langer-Schwartz theory. Thermodynamic and kinetic data are taken from commercially available CALPHAD software, but reliable interfacial energy data for precipitates needed for the calculations is often lacking. While models exist to approximate these interfacial energies, this study has focused on deriving more reliable estimates by comparison with experimental data. By performing simulations with thermal histories, nucleation sites, and precipitate morphologies that closely replicate experimental data found in literature, the interfacial energies were optimized until volume fraction and mean radius values closely matched the published data. Using this technique, interfacial energy values have been determined for carbides in Grade 22 low alloy steels, delta phase in Ni 625 and 718, SPhase in Al 2024, and Q’ and β’’ in Al 6111, and can be used for future predictive precipitation simulations.

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Simulation of Precipitation Kinetics with Non-Spherical Particles

Cited by 22 publications

References 25 publications

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

High-Throughput and Systematic Study of Phase Transformations and Metastability Using Dual-Anneal Diffusion Multiples

Optimization of Interfacial Energy for Langer-Schwartz Based Precipitation Simulations

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