The Role of Dispersions in Modeling the Kinetics of Phase Transformations

2011 ◽  
Vol 172-174 ◽  
pp. 279-284 ◽  
Author(s):  
Mohamed Gouné ◽  
Philippe Maugis
Keyword(s):  
Experimental Data ◽  
Phase Transformations ◽  
Microstructural Evolution ◽  
General Model ◽  
Bainitic Transformation ◽  
Incorrect Prediction ◽  
Classical Models ◽  
Kinetics Of ◽  
Overall Kinetics

In classical models of microstructural evolution, the natural dispersion existing in the samples is often neglected. In this paper, we propose a general model that takes into account the dispersion. This model is applied to two cases of phase transformations in steels: the first one concerns the bainitic transformation and the second is dedicated to austenite to ferrite transformation. Through these examples, we show that not taking account the effects of dispersion in the model can lead to (i) incorrect prediction of the overall kinetics or (ii) an incorrect parameter fitting of the experimental data.

Precipitation and Recrystallization in an Al-Mg-Sc Alloy

2006 ◽  
Vol 519-521 ◽  
pp. 1647-1652 ◽  
Author(s):  
R. Roumina ◽  
Chad W. Sinclair ◽  
F. Fazeli
Keyword(s):  
Microstructural Evolution ◽  
Annealing Temperature ◽  
Microstructural Stability ◽  
Rolled Material ◽  
Recrystallization Kinetics ◽  
Cold Rolled ◽  
Kinetics Of Precipitation ◽  
Kinetics Of ◽  
Relative Kinetics

The addition of scandium severely retards the recrystallization of Al-Sc alloys when it is present in the form of fine Al3Sc precipitates. Though many studies have focused on the role of Al3Sc in the deformation and recrystallization of pre-aged or hot deformed Al-Sc alloys, recent studies on the annealing response of solutionized and cold rolled material have shown various possibilities for microstructural stability depending on the relative kinetics of precipitation and recrystallization. In this study, the microstructural evolution of solutionized and cold rolled Al- 2.9wt%Mg-0.16wt%Sc has been followed in order to evaluate the role of imposed strain and annealing temperature on the recrystallization kinetics.

Electron Microscopy Observations on the Role of Twinning in the Evolution of Microstructures

2002 ◽  
Vol 8 (4) ◽  
pp. 247-256 ◽  
Author(s):  
U. Dahmen ◽  
C.J.D. Hetherington ◽  
V. Radmilovic ◽  
E. Johnson ◽  
S.Q. Xiao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Transformations ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Equilibrium Shape ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Multiple Twinning

Twinning plays an important role in phase transformations and can have significant effects on microstructural evolution. Different roles of twinning in the development of microstructures during precipitation and phase transformations are reviewed and illustrated with examples from investigations by high-resolution electron microscopy, including the effect of multiple twinning on the development of Ge precipitates in Al-Ge and Ag-Ge alloys, the twin dissociation of grain boundaries in Au, the formation of hexagonal Si at twin intersections and the effect of twin boundaries on the equilibrium shape of Pb inclusions in Al.

Mathematical research of the phase transformation kinetics of alloyed steel

2019 ◽  
Vol 85 (12) ◽  
pp. 25-32
Author(s):  
A. S. Kurkin
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Phase Transformations ◽  
Diffusion Processes ◽  
Kinetic Equations ◽  
Transformation Process ◽  
Avrami Equation ◽  
Published Data ◽  
Transformation Rate ◽  
Kinetics Of

Regulation of the process parameters allows obtaining the desired properties of the metal. Computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. Methods of mathematical modeling are used to study the main diffusion and diffusion-free processes of transformations in alloyed steels during heating and cooling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov – Avrami and Austin – Rickett equations which describe in different ways the time dependence of the diffusion transformation rate and attained degree of transformation has been carried out. It is shown that the Austin – Rickett equation is equivalent to the Kolmogorov – Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov – Avrami equation in modeling the kinetics of ferrite-pearlite and bainite transformations and validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon – Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and disadvantages of the Koistinen – Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the transformation degree, similar to the Kolmogorov – Avrami and Austin – Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the equations is developed, providing the minimum standard deviation of the constructed dependence from the initial experimental data. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development for some steels is revealed. The advantage of using equations of the Austin – Rickett type when constructing models from a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in modeling diffusion processes of austenite decomposition to description of the processes of formation and decomposition of martensite in alloyed steels.

Kinetics of the Tial3 Formation From Al/Ti Thin Films

1999 ◽  
Vol 563 ◽  
Author(s):  
X. Federspiel ◽  
M. Ignat ◽  
F. Voiron ◽  
H. Fujimoto ◽  
T. Marieb
Keyword(s):  
Integrated Circuits ◽  
Boundary Diffusion ◽  
Microstructural Analysis ◽  
Electrical Measurements ◽  
Nucleation Frequency ◽  
Transmission Electron ◽  
Secondary Ions ◽  
Classical Models ◽  
Kinetics Of

AbstractThe interfacial reactions that may occur from the ageing of integrated circuits during operation will change their properties and produce failures. It is crucial to understand the phenomena that controls these reactions and their kinetics.The object of this work was to establish the role of impurities and grain size on the growth rate of TiAI3 from Al/Ti interfaces. The kinetic study consisted of different annealings followed by electrical measurements. These data were correlated with microstructural analysis and composition evolution from Transmission Electron Microscopy (TEM), Secondary Ions Mass Spectroscopy (SIMS).The kinetic data were fitted using a combination of classical models (parabolic, Avrami, Aronson) and complemented by a simulation, which accounts for the nucleation frequency and the grain boundary diffusion. The growth simulations were compared to microstructures observations using TEM.

A New Approach to Study the Degradation of the Organic Pollutants by A-Doped MxOy/B Photocatalysts

2021 ◽  
Author(s):  
Mojtaba Arabameri ◽  
Hadis Bashiri
Keyword(s):  
Experimental Data ◽  
Organic Pollutants ◽  
Vital Role ◽  
Effective Concentration ◽  
Computational Method ◽  
Operational Parameters ◽  
New Approach ◽  
New Variables ◽  
Kinetics Of

Abstract This work presents a new approach and a comprehensive mechanism to study the kinetics of the photodegradation of the organic pollutants. The vital role of various operational factors on the degradation of the organic pollutants is explained using this method. The proposed approach is based on the simple strategies and a powerful computational method. Two new variables “the effective concentration of photon” (Ieff) and “the effective concentration of the reactive-centers” (RC) are defined to better understanding the effect of operational parameters on the organic pollutants photodegradation. The optimum conditions of the photocatalytic degradation can be determined with the help of this method. This approach was used to study the kinetics of photodegradation of the organic pollutants on the A - doped MxOy/B photocatalysts. The provided mechanism has been examined with the some experimental data. The high correlations between the experimental data and the fitting results under different conditions prove this mechanism could be reliable.

Role of sample size in the nucleation kinetics of phase transformations in steel alloys

2005 ◽  
Vol 16 (1-4) ◽  
pp. 55-58 ◽  
Author(s):  
David J. Fair ◽  
Rakesh Venkatesh ◽  
Bruce Boghosian ◽  
Douglas M. Matson
Keyword(s):  
Sample Size ◽  
Phase Transformations ◽  
Nucleation Kinetics ◽  
Steel Alloys ◽  
Kinetics Of

A kinetic study of the phase transformations in Al2O3 and Na2O · 6Al2O3 by a combined use of 27Al MAS NMR spectroscopy and x-ray diffraction: Importance of nucleation

1991 ◽  
Vol 6 (12) ◽  
pp. 2701-2705 ◽  
Author(s):  
S. Prabakar ◽  
K.J. Rao ◽  
C.N.R. Rao
Keyword(s):  
Nmr Spectroscopy ◽  
Phase Transformations ◽  
Mas Nmr ◽  
X Ray Diffraction ◽  
X Ray ◽  
Combined Use ◽  
27Al Mas Nmr ◽  
First Time ◽  
Kinetics Of

Phase transformations of Al2O3 and Na2O · 6Al2O3 prepared by the gel route have been investigated for the first time by 27Al MAS NMR spectroscopy in combination with x-ray diffraction. Of particular interest in the study is the kinetics of the γ → α and γ → β transformations, respectively, in these two systems. Analysis of the kinetic data shows the important role of nucleation in both these transformations.

scholarly journals Role of TLR4 in Persistent Leptospira interrogans Infection: A Comparative In Vivo Study in Mice

2021 ◽  
Vol 11 ◽  
Author(s):  
Nisha Nair ◽  
Mariana S. Guedes ◽  
Adeline M. Hajjar ◽  
Catherine Werts ◽  
Maria Gomes-Solecki
Keyword(s):  
Innate Immune ◽  
High Dose ◽  
Wild Type ◽  
Immune Markers ◽  
Lethal Infection ◽  
Tlr4 Gene ◽  
Kinetics Of ◽  
Overall Kinetics

Toll-Like Receptor (TLR) 4, the LPS receptor, plays a central role in the control of leptospirosis and absence of TLR4 results in lethal infection in mice. Because human TLR4 does not sense the atypical leptospiral-LPS, we hypothesized that TLR4/MD-2 humanized transgenic mice (huTLR4) may be more susceptible to leptospirosis than wild-type mice, and thus may constitute a model of acute human leptospirosis. We infected huTLR4 mice, which express human TLR4 but not murine TLR4, with a high dose of L. interrogans serovar Copenhageni FioCruz (Leptospira) in comparison to C57BL/6J wild-type (WT) and, as a control, a congenic strain in which the tlr4 coding sequences are deleted (muTLR4Lps-del). We show that the huTLR4 gene is fully functional in the murine background. We found that dissemination of Leptospira in blood, shedding in urine, colonization of the kidney and overall kinetics of leptospirosis progression is equivalent between WT and huTLR4 C57BL/6J mice. Furthermore, inflammation of the kidney appeared to be subdued in huTLR4 compared to WT mice in that we observed less infiltrates of mononuclear lymphocytes, less innate immune markers and no relevant differences in fibrosis markers. Thus, huTLR4 mice showed less inflammation and kidney pathology, and are not more susceptible to leptospirosis than WT mice. This study is significant as it indicates that one intact TLR4 gene, be it mouse or human, is necessary to control acute leptospirosis.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

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