scholarly journals Voronoi diagram based simulation and experimental validation of austenite in C22 and C35 steels

10.30544/482 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 31-42
Author(s):  
Sanchu S ◽  
Biju N ◽  
V. N.N. Namboothiri
Keyword(s):  
Heat Treatment ◽  
Voronoi Diagram ◽  
Experimental Validation ◽  
Maximum Error ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Microstructure Modeling ◽  
Geometrical Features ◽  
Simulation Results

This paper examines the ability of power Voronoi diagram assisted simulation in microstructure modeling during heat treatment. A model is developed for predicting fraction of austenite evolved during continuous heating of steel to austenite range, by integrating geometrical features of power Voronoi diagram and classical nucleation theory. From the simulation results, it is possible to predict the transformed fraction. The simulation results are validated using experiments conducted on two varieties of steels. The maximum error obtained is 2.08%. Thus, power Voronoi assisted simulation can be considered as an effective tool in modeling microstructure evolution during austenitization.

Microstructural evolution during decomposition and crystallization of the Cu60Zr20Ti20 amorphous alloy

2004 ◽  
Vol 19 (2) ◽  
pp. 505-512 ◽  
Author(s):  
A. Concustell ◽  
Á. Révész ◽  
S. Suriñach ◽  
L.K. Varga ◽  
G. Heunen ◽  
...  
Keyword(s):  
Amorphous Matrix ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Isothermal Heat Treatments ◽  
Crystallization Stage

The effect of continuous heating and isothermal heat treatments on ductile Cu60Zr20Ti20 amorphous ribbons was monitored by differential scanning calorimetry, x-ray diffraction, synchrotron radiation transmission, and high-resolution transmission electron microscopy. Upon continuous heating, the alloy exhibited a glass transition, followed by a supercooled liquid region and two exothermic crystallization stages. Decomposition of the amorphous phase was also observed. The first crystallization stage resulted in the formation of a nanocomposite structure with hexagonal Cu51Zr14 particles embedded in the amorphous matrix, while in the second crystallization stage hexagonal Cu2TiZr-like phase was precipitated. The released enthalpies were 19 J/g and 30 J/g for each crystallization stage. Crystallization kinetics was studied by the classical nucleation theory. Deviations from the Johnson–Mehl–Avrami–Kolmogorov theory may be explained by the contribution of the decomposition of the amorphous matrix.

Molecular Dynamics Based Analysis of Nucleation and Surface Energy of Droplets in Supersaturated Vapors of Methane and Ethane

2008 ◽  
Author(s):  
Jadran Vrabec ◽  
Martin Horsch ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Surface Energy ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Size Dependence ◽  
Md Simulations ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Specific Surface Energy ◽  
Simulation Results

Molecular dynamics (MD) simulations are applied for studying homogeneous nucleation during condensation of supersaturated vapors of methane and ethane. Nucleation processes are characterized by the nucleation rate, i.e. the number of stable droplets produced per volume and time. Nucleation rates from simulations are compared to the classical nucleation theory (CNT) and a model that introduces a size dependence of the specific surface energy. CNT is found to agree well with the simulation results, deviations are throughout lower than three orders of magnitude.

Crystallization of Supercooled Zr41Ti14Cu12Ni10B23 Melts During Continuous Heating and Cooling

1998 ◽  
Vol 554 ◽  
Author(s):  
Jan Schroers ◽  
Andreas Masuhr ◽  
Ralf Busch ◽  
William L. Johnson
Keyword(s):  
Cooling Rate ◽  
Bulk Sample ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Diffusion Limited ◽  
Surface Nucleation ◽  
The Difference

AbstractThe crystallization behavior of the bulk glass forming Zr41Ti14Cu12Ni10Be23 liquid was studied under different heating and cooling rates. Investigations were performed in high purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk sample. A rate of about 1 K/s is sufficient to circumvent crystallization of the melt while cooling from the equilibrium melt. In contrast, upon heating a rate of more than 150 K/s is necessary to avoid crystallization of Zr41Ti14Cu12Ni10Be23 samples. The difference between the critical heating and cooling rate is discussed within classical nucleation theory and diffusion limited crystal growth. The calculated difference of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are expose to different growth rates.

scholarly journals Phase-field modeling of grain evolutions in additive manufacturing from nucleation, growth, to coarsening

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Min Yang ◽  
Lu Wang ◽  
Wentao Yan
Keyword(s):  
Additive Manufacturing ◽  
Phase Field ◽  
Field Model ◽  
Three Dimensional ◽  
Phase Field Model ◽  
Nucleation Theory ◽  
Experimental Result ◽  
Classical Nucleation Theory ◽  
Validation Experiment ◽  
Powder Particles

AbstractA three-dimensional phase-field model is developed to simulate grain evolutions during powder-bed-fusion (PBF) additive manufacturing, while the physically-informed temperature profile is implemented from a thermal-fluid flow model. The phase-field model incorporates a nucleation model based on classical nucleation theory, as well as the initial grain structures of powder particles and substrate. The grain evolutions during the three-layer three-track PBF process are comprehensively reproduced, including grain nucleation and growth in molten pools, epitaxial growth from powder particles, substrate and previous tracks, grain re-melting and re-growth in overlapping zones, and grain coarsening in heat-affected zones. A validation experiment has been carried out, showing that the simulation results are consistent with the experimental results in the molten pool and grain morphologies. Furthermore, the grain refinement by adding nanoparticles is preliminarily reproduced and compared against the experimental result in literature.

scholarly journals On the Role of Poly-Glutamic Acid in the Early Stages of Iron(III) (Oxy)(hydr)oxide Formation

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 715
Author(s):  
Miodrag J. Lukić ◽  
Felix Lücke ◽  
Teodora Ilić ◽  
Katharina Petrović ◽  
Denis Gebauer
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Phase Separation ◽  
Fourier Transform Infrared Spectroscopy ◽  
Fourier Transform Infrared ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Oxide Formation ◽  
Early Stages ◽  
Titration Assay

Nucleation of minerals in the presence of additives is critical for achieving control over the formation of solids in biomineralization processes or during syntheses of advanced hybrid materials. Herein, we investigated the early stages of Fe(III) (oxy)(hydr)oxide formation with/without polyglutamic acid (pGlu) at low driving force for phase separation (pH 2.0 to 3.0). We employed an advanced pH-constant titration assay, X-ray diffraction, thermal analysis with mass spectrometry, Fourier Transform infrared spectroscopy, and scanning electron microscopy. Three stages were observed: initial binding, stabilization of Fe(III) pre-nucleation clusters (PNCs), and phase separation, yielding Fe(III) (oxy)(hydr)oxide. The data suggest that organic–inorganic interactions occurred via binding of olation Fe(III) PNC species. Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed a plausible interaction motif and a conformational adaptation of the polypeptide. The stabilization of the aqueous Fe(III) system against nucleation by pGlu contrasts with the previously reported influence of poly-aspartic acid (pAsp). While this is difficult to explain based on classical nucleation theory, alternative notions such as the so-called PNC pathway provide a possible rationale. Developing a nucleation theory that successfully explains and predicts distinct influences for chemically similar additives like pAsp and pGlu is the Holy Grail toward advancing the knowledge of nucleation, early growth, and structure formation.

scholarly journals An Analysis of Acoustic Cavitation Thresholds of Water Based on the Incubation Time Criterion Approach

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 134
Author(s):  
Ivan Smirnov ◽  
Natalia Mikhailova
Keyword(s):  
Incubation Time ◽  
Dynamic Strength ◽  
Acoustic Cavitation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Accurate Estimation ◽  
Ultrasound Frequency ◽  
Time Criterion ◽  
Good Potential ◽  
Cavitation Threshold

Researchers are still working on the development of models that facilitate the accurate estimation of acoustic cavitation threshold. In this paper, we have analyzed the possibility of using the incubation time criterion to calculate the threshold of the onset of acoustic cavitation depending on the ultrasound frequency, hydrostatic pressure, and temperature of a liquid. This criterion has been successfully used by earlier studies to calculate the dynamic strength of solids and has recently been proposed in an adapted version for calculating the cavitation threshold. The analysis is carried out for various experimental data for water presented in the literature. Although the criterion assumes the use of macroparameters of a liquid, we also considered the possibility of taking into account the size of cavitation nuclei and its influence on the calculation result. We compared the results of cavitation threshold calculations done using the incubation time criterion of cavitation and the classical nucleation theory. Our results showed that the incubation time criterion more qualitatively models the results of experiments using only three parameters of the liquid. We then discussed a possible relationship between the parameters of the two approaches. The results of our study showed that the criterion under consideration has a good potential and can be conveniently used for applications where there are special requirements for ultrasound parameters, maximum negative pressure, and liquid temperature.

scholarly journals Homogeneous Freezing of Water Using Microfluidics

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 223
Author(s):  
Mark D. Tarn ◽  
Sebastien N. F. Sikora ◽  
Grace C. E. Porter ◽  
Jung-uk Shim ◽  
Benjamin J. Murray
Keyword(s):  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Recent Theory ◽  
Water Droplets ◽  
Microfluidic Platforms ◽  
High Throughput Method ◽  
Theoretical Predictions ◽  
New Instrumentation ◽  
Controlled Environments ◽  
Homogeneous Freezing

The homogeneous freezing of water is important in the formation of ice in clouds, but there remains a great deal of variability in the representation of the homogeneous freezing of water in the literature. The development of new instrumentation, such as droplet microfluidic platforms, may help to constrain our understanding of the kinetics of homogeneous freezing via the analysis of monodisperse, size-selected water droplets in temporally and spatially controlled environments. Here, we evaluate droplet freezing data obtained using the Lab-on-a-Chip Nucleation by Immersed Particle Instrument (LOC-NIPI), in which droplets are generated and frozen in continuous flow. This high-throughput method was used to analyse over 16,000 water droplets (86 μm diameter) across three experimental runs, generating data with high precision and reproducibility that has largely been unrepresented in the microfluidic literature. Using this data, a new LOC-NIPI parameterisation of the volume nucleation rate coefficient (JV(T)) was determined in the temperature region of −35.1 to −36.9 °C, covering a greater JV(T) compared to most other microfluidic techniques thanks to the number of droplets analysed. Comparison to recent theory suggests inconsistencies in the theoretical representation, further implying that microfluidics could be used to inform on changes to parameterisations. By applying classical nucleation theory (CNT) to our JV(T) data, we have gone a step further than other microfluidic homogeneous freezing examples by calculating the stacking-disordered ice–supercooled water interfacial energy, estimated to be 22.5 ± 0.7 mJ m−2, again finding inconsistencies when compared to theoretical predictions. Further, we briefly review and compile all available microfluidic homogeneous freezing data in the literature, finding that the LOC-NIPI and other microfluidically generated data compare well with commonly used non-microfluidic datasets, but have generally been obtained with greater ease and with higher numbers of monodisperse droplets.

scholarly journals Low-temperature nucleation anomaly in silicate glasses shown to be artifact in a 5BaO·8SiO2 glass

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xinsheng Xia ◽  
D. C. Van Hoesen ◽  
Matthew E. McKenzie ◽  
Randall E. Youngman ◽  
K. F. Kelton
Keyword(s):  
Nucleation Rate ◽  
Experimental Approach ◽  
Cluster Formation ◽  
Heating Time ◽  
Silicate Glasses ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Real Phenomenon ◽  
Satisfactory Answer ◽  
Over 40 Years

AbstractFor over 40 years, measurements of the nucleation rates in a large number of silicate glasses have indicated a breakdown in the Classical Nucleation Theory at temperatures below that of the peak nucleation rate. The data show that instead of steadily decreasing with decreasing temperature, the work of critical cluster formation enters a plateau and even starts to increase. Many explanations have been offered to explain this anomaly, but none have provided a satisfactory answer. We present an experimental approach to demonstrate explicitly for the example of a 5BaO ∙ 8SiO2 glass that the anomaly is not a real phenomenon, but instead an artifact arising from an insufficient heating time at low temperatures. Heating times much longer than previously used at a temperature 50 K below the peak nucleation rate temperature give results that are consistent with the predictions of the Classical Nucleation Theory. These results raise the question of whether the claimed anomaly is also an artifact in other glasses.

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