scholarly journals Application of Computer Simulation to Study the Features of the Austenite Isothermal Transformation in Steels

2019 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
Yu.V. Yudin ◽  
M.V. Maisuradze ◽  
A.A. Kuklina ◽  
P.D. Lebedev
Keyword(s):  
Phase Transition ◽  
Computer Simulation ◽  
Solid State ◽  
Isothermal Transformation ◽  
Avrami Equation ◽  
Kinetic Curves ◽  
Simulation Results ◽  
Experimental Kinetics ◽  
Kinetics Of ◽  
New Phase

An algorithm was developed for the simulation of a phase transition in solid state whichmakes it possible to obtain the kinetic curves of transformation under different initialconditions (the number and arrangement of new phase nuclei, the distance betweenthe nearest nuclei). The simulation results were analyzed using the Kolmogorov-Johnson-Mehl-Avrami equation and the corresponding coefficients were determined.The correlation between the simulation results and the experimental kinetics of theaustenite isothermal transformation in alloyed steels was shown.

scholarly journals Solid-state phase transition in n-alkanes of different parity

2021 ◽  
Vol 2086 (1) ◽  
pp. 012182
Author(s):  
S A Gureva ◽  
A K Borisov ◽  
V A Marikhin ◽  
V M Egorov
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Solid State ◽  
Ftir Spectroscopy ◽  
Structural Transition ◽  
Structural Phase ◽  
First Order ◽  
Structure Rearrangement ◽  
Kinetics Of ◽  
New Phase

Abstract The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of tricosane C23H48 and tetracosane C24H50 was studied by DSC and FTIR spectroscopy. The initial nuclei location of the new phase was revealed. The process of crystal structure rearrangement is initiated in the interlayers between neighboring lamellar for odd tricosane, while the nanonuclei in even tetracosane arise in the crystalline lamella cores. Thus, the influence of the number evenness of carbon atoms in the n-alkanes chains on the first-order structural phase transition has been proved.

Theory of nucleation in solid state reactions

1968 ◽  
Vol 46 (2) ◽  
pp. 111-116 ◽  
Author(s):  
A. R. Allnatt ◽  
P. W. M. Jacobs
Keyword(s):  
Solid State ◽  
Approximate Model ◽  
Single Step ◽  
Solid State Reactions ◽  
Avrami Equation ◽  
Nucleation Process ◽  
Special Cases ◽  
New Equation ◽  
Kinetics Of ◽  
Short Times

The theory of nucleation in solid state reactions is formulated in a general way and a solution to the problem of multi-step nucleation obtained. Two special cases of the general formulation are considered: the second of these corresponds to Bagdassarian's approximate model and some corrections to his treatment are pointed out. A new equation describing the kinetics of a solid state reaction, which involves multi-step nucleation followed by a constant and isotropic rate of growth, is derived. This equation is termed the generalized Avrami equation since it removes the restriction, in Avrami's treatment, of a single-step nucleation process. Erofeev's analysis of the problem is shown to be valid only in the limit of short times: the generalized Avrami equation reduces to Erofeev's equation in this limit.

scholarly journals Precessing Ball Solitons in Kinetics of a Spin-Flop Phase Transition

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
V. V. Nietz
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Uniaxial Anisotropy ◽  
Precession Frequency ◽  
Initial Condition ◽  
Configuration Energy ◽  
Wide Range ◽  
Kinetics Of ◽  
New Phase ◽  
The Magnetic Field

The fundamentals of precessing ball solitons (PBS), arising as a result of the energy fluctuations during spin-flop phase transition induced by a magnetic field in antiferromagnets with uniaxial anisotropy, are presented. The PBS conditions exist within a wide range of amplitudes and energies, including negative energies relative to an initial condition. For each value of the magnetic field, there exists a precession frequency for which a curve of PBS energy passes through a zero value (in bifurcation point), and hence, in the vicinity of this point the PBS originate with the highest probability. The characteristics of PBS, including the time dependences of configuration, energy, and precession frequency, are considered. As a result of dissipation, the PBS transform into the macroscopic domains of a new phase.

Silicon Carbide Solid-Phase Epitaxy on a Microporous Substratum

2012 ◽  
Vol 326-328 ◽  
pp. 243-248 ◽  
Author(s):  
Galina I. Zmievskaya ◽  
Anna L. Bondareva ◽  
V.V. Savchenko ◽  
Tatiana V. Levchenko
Keyword(s):  
Phase Transition ◽  
Computer Simulation ◽  
Silicon Carbide ◽  
Solid State ◽  
Stochastic Model ◽  
Solid Phase ◽  
Inert Gas ◽  
Self Organization ◽  
Solid Phase Epitaxy ◽  
Initial Stage

The action flux of ions of inert gas on the substratum Si (100) leads to porosity into the crystal lattice and self-organization of these defects. The kinetic stochastic model of the phase transition at the initial stage is applied to find distributions of defects in sizes and on their coordinates in the layers. The accumulation of stress is determined by computer simulation. Layers of pores and cracks precede to solid state epitaxy of silicon carbide.

Modeling and Simulation of Nucleation and Growth Transformations with Nucleation on Interfaces of Kelvin Polihedra Network

2018 ◽  
Vol 930 ◽  
pp. 299-304 ◽  
Author(s):  
Guilherme Dias da Fonseca ◽  
André Luiz Moraes Alves ◽  
Marcos Felipe Braga da Costa ◽  
Mariana Sizenando Lyrio ◽  
Weslley L.S. Assis ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Grain Boundaries ◽  
Nucleation And Growth ◽  
Primary Phase ◽  
Metallic Materials ◽  
Computational Simulations ◽  
The Matrix ◽  
Simulation Results ◽  
New Phase ◽  
Over Time

Nucleation is a phenomenon associated to the start of the new phase, from a primary phase, named matrix. Growth is the increase in size of this new phase over time. In metallic materials, the nucleation may take place on the grain boundaries of the primary phase. A network of Kelvin polyhedra was used in this paper to represent the grains. A computer simulation was performed in which nucleation took places at the faces, edges and vertices of this polyhedral network. The Causal cone method was employed in the simulations. The results of the present computational simulations were compared with the classical Johnson Mehl-Avrami-Kolmogorov (JMAK) as well as with Cahn model for nucleation at the grain boundaries. JMAK theory considers nuclei to be uniform randomly located within the matrix. Cahn analytical model specifies that nucleation takes place on random planes. For a small number of nuclei, the simulations approached the JMAK model whereas as the number of nuclei increased the simulation results agree with Cahn's theory. Reasons for this are fully discussed.

scholarly journals The influence of conformational defects on the development of structural phase transition in tetracosane C24H50

2021 ◽  
Vol 2103 (1) ◽  
pp. 012091
Author(s):  
S A Gureva ◽  
V A Marikhin ◽  
L P Myasnikova ◽  
B Z Volchek ◽  
D A Medvedeva
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Ftir Spectroscopy ◽  
Melting Temperature ◽  
Structural Phase Transition ◽  
Structural Transition ◽  
Structural Phase ◽  
First Order ◽  
Solid Phases ◽  
Kinetics Of

Abstract The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of even tetracosane C24H50 was studied by FTIR spectroscopy. The existence of many irregular conformers in solid phases of tetracosane, the concentration of which reaches a maximum when approaching the melting temperature, has been demonstrated. The existence of these defective molecules promotes transitions between different rotator phases in the solid state.

scholarly journals The Kinetics of Phase Transition of Austenite to Ferrite in Medium-Carbon Microalloy Steel

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1986
Author(s):  
Liushun Wu ◽  
Kunlong Liu ◽  
Yun Zhou
Keyword(s):  
Phase Transition ◽  
Volume Fraction ◽  
High Strength ◽  
Effect Of Temperature ◽  
Avrami Equation ◽  
Validation Data ◽  
Medium Carbon ◽  
Hot Rolled ◽  
Kinetics Of ◽  
Transition Kinetic

To reduce energy and resource consumption, high-strength hot-rolled rebars with yield strengths of ≥400 MPa (HRB500) and ≥500 MPa (HRB600) have been designed and produced in recent years. Optimizing the microstructure in the steel to improve strength necessitates determining the kinetics of the phase transition of austenite to polygonal ferrite. Therefore, in the study, the effect of temperature and holding time on the volume fraction of ferrite is investigated in HRB500 and HRB600 steels. Experimental results show that the ferrite percentage initially increases with an increase in temperature and then decreases as the temperature increases from 600 to 730 °C. The optimum temperature range is 680–700 °C for HRB500 steel and 650–680 °C for HRB600 steel. Based on the Johnson–Mehl–Avrami equation, phase transition kinetic models are established. Model predictions are consistent with the validation data. Thus, this study establishes a reference for studying ferrite formation during cooling.

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