Determination of the Grain Coarsening Temperature in Nb Microalloyed Steels by Multiphase-Field Model

2016 ◽  
Vol 879 ◽  
pp. 921-925
Author(s):  
Jeong Min Kim ◽  
Sok Yun Hong ◽  
Ji Hun Jang ◽  
Kyung Jong Lee
Keyword(s):  
Field Model ◽  
Volume Fraction ◽  
Mean Field ◽  
Time Dependent ◽  
Microalloyed Steels ◽  
Pinning Force ◽  
Grain Coarsening ◽  
Dimensional Growth ◽  
Kinetics Of

The grain coarsening temperature in Nb microalloyed steels is investigated by multiphase-field model. In this study, the pinning force is treated as time-dependent using mean-field kinetics of precipitates including volume fraction and their size. The grain size is calculated with time under various temperature range. The grain coarsening temperature is determined by the ratio of the largest radius of grain vs. the average grain radius criteria (Rmax / Ravg > 2.94) in two-dimensional growth. Through this model, it is possible to simulate grain growth in microalloyed steels more precisely.

scholarly journals Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Wenjun Song ◽  
Min Lei ◽  
Mingpan Wan ◽  
Chaowen Huang
Keyword(s):  
Phase Transformation ◽  
Volume Fraction ◽  
Austenite Formation ◽  
Steel Matrix ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Continuous Cooling ◽  
The Matrix ◽  
Dimensional Growth ◽  
Kinetics Of

In this study, the phase transformation behaviour of the carburised layer and the matrix of 23CrNi3Mo steel was comparatively investigated by constructing continuous cooling transformation (CCT) diagram, determining the volume fraction of retained austenite (RA) and plotting dilatometric curves. The results indicated that Austenite formation start temperature (Ac1) and Austenite formation finish temperature (Ac3) of the carburised layer decreased compared to the matrix, and the critical cooling rate (0.05 °C/s) of martensite transformation is significantly lower than that (0.8 °C/s) of the matrix. The main products of phase transformation in both the carburised layer and the matrix were martensite and bainite microstructures. Moreover, an increase in carbon content resulted in the formation of lamellar martensite in the carburised layer, whereas the martensite in the matrix was still lath. Furthermore, the volume fraction of RA in the carburised layer was higher than that in the matrix. Moreover, the bainite transformation kinetics of the 23CrNi3Mo steel matrix during the continuous cooling process indicated that the mian mechanism of bainite transformation of the 23CrNi3Mo steel matrix is two-dimensional growth and one-dimensional growth.

Transient kinetics of nucleation and crystallization: Part II. Crystallization

1991 ◽  
Vol 6 (10) ◽  
pp. 2097-2102 ◽  
Author(s):  
G. Shi ◽  
J.H. Seinfeld
Keyword(s):  
Experimental Data ◽  
Large Time ◽  
Volume Fraction ◽  
Time Dependent ◽  
Transient Kinetics ◽  
Amorphous Phases ◽  
Time Limits ◽  
The Stability ◽  
Analytical Expressions ◽  
Kinetics Of

Analytical expressions for the time-dependent crystallized volume fraction are derived from new results for the transient rate of nucleation reported in Part I. Conventional formulations that have been used in interpreting crystallization experimental data and for assessing the stability of amorphous phases are shown to be large time limits of the newly derived expressions. An approach for assessing the stability of an amorphous phase is proposed.

Microstructure Evaluation for Time Dependent Nucleation Protocols in KJMA Kinetics

1999 ◽  
Vol 580 ◽  
Author(s):  
Eloi Pineda ◽  
Daniel Crespo
Keyword(s):  
Mean Field ◽  
Quantitative Agreement ◽  
Nucleation And Growth ◽  
Time Dependent ◽  
First Order ◽  
Microstructure Evaluation ◽  
The Mean ◽  
Dependent Growth ◽  
First Order Phase

AbstractThe microstructure developed in a first order phase transformation is obtained using a populational extension of the Kolmogorov, Johnson-Mehl and Avrami (KJMA) model, PKJMA. PKJMA allows one to determine the grain size distribution resulting from nucleation and growth kinetics. PKJMA is grounded on the mean field hypothesis that the free space around the growing grains is randomly distributed, independent of the grain radius. Although this approach is perfectly valid for the case of constant nucleation, a detailed analysis of the model shows that this hypothesis does not hold in the case of time dependent nucleation protocols or pre-existing nuclei. In this work, the PKJMA model has been improved by estimating the average free surface around the grains as a function of their radius and the time elapsed since nucleation. The resulting model gives quantitative determination of the microstructure developed under a variety of nucleation and growth processes: pre-existing nuclei, constant nucleation, and the combination of both mechanisms, constant and radius dependent growth rates. Comparison with Monte Carlo simulations, showing a quantitative agreement will be presented.

scholarly journals Amorphous alloys and differential scanning calorimetry (DSC)

2021 ◽  
Author(s):  
Dora Janovszky ◽  
Maria Sveda ◽  
Anna Sycheva ◽  
Ferenc Kristaly ◽  
Ferenc Zámborszky ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Volume Fraction ◽  
Data Interpretation ◽  
Glass Temperature ◽  
Scanning Calorimetry ◽  
Scientific Papers ◽  
Kinetics Of ◽  
Temperature Crystallization

AbstractA remarkable number of scientific papers are available in the literature about the bulk amorphous alloys and metallic glasses. Today, DSC is an essential tool for amorphous alloys research and development, and of course for quality assurance. In many cases, users seek to examine the determination of only one or two properties, although much more information can be obtained from the measurements. The research involved structural relaxation, Curie temperature, glass temperature, crystallization, phase separation, nanocrystalline volume fraction, melting point and liquidus temperature determination subjects and kinetics of microstructural transformations induced by thermal treatment. We collected and present the information that can be obtained with this technique and draws the reader’s attention to some potential problems related to data interpretation.

The Effect of Surface on the Kinetics of Crystallization of Pd-Si Glassy Metals

1986 ◽  
Vol 80 ◽  
Author(s):  
A. Calka ◽  
A. P. Radliński
Keyword(s):  
Nucleation Rate ◽  
Metallic Glasses ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Growth Morphology ◽  
Thermally Activated ◽  
Glassy Metals ◽  
Dimensional Growth ◽  
Kinetics Of ◽  
Effect Of Surface

IntroductionThe isothermal devitrification by nucleation and growth of metallic glasses is usually analysed using the Johnson-Mehl-Avrami (JMA) equation: where x is the volume fraction crystallized after time t, K is a thermally activated rate constant, τ is the nucleation lag time, and n is the so-called Avrami exponent. If the nucleation conditions and growth morphology remain unchanged during the crystallization then n is a constant. There is ample experimental evidence that for the Pd-Si system the growth process is either eutectic or interface-controlled. Therefore, one expects n=3 for crystallization on pre-existing nuclei (zero nucleation rate) and n=4 for crystallization at constant nucleation rate, both for three-dimensional growth. When the growth dimensionality is decreased by one these values decrease stepwise by one as well.

SPINODAL DECOMPOSITION IN HYDROGEN-BONDED POLYMER BLENDS

1996 ◽  
Vol 10 (25) ◽  
pp. 1219-1226 ◽  
Author(s):  
E.K. HOBBIE ◽  
G. MERKLE ◽  
B.J. BAUER ◽  
C.C. HAN
Keyword(s):  
Spinodal Decomposition ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Time Resolved ◽  
Slow Kinetics ◽  
Ising Systems ◽  
Composition Fluctuations ◽  
Kinetics Of ◽  
Hydrogen Bonded

Time-resolved small-angle neutron-scattering (SANS) studies of spinodal decomposition in hydrogen-bonded blends of polystyrene and poly(butylmethacrylate) reveal extremely slow kinetics of phase separation in the vicinity of the critical point. The experimental data are interpreted within the context of a mean-field model that predicts energetic barriers to extended composition fluctuations. The scenario bears a resemblance to dynamic critical phenomena in Ising systems with coupling to a set of mobile impurities.

Extraction of dithiocarbamic acids from solutions of their salts

1982 ◽  
Vol 47 (11) ◽  
pp. 2876-2881 ◽  
Author(s):  
Drahomír Oktavec ◽  
Bohumil Síleš ◽  
Ján Remeň ◽  
Václav Konečný ◽  
Ján Garaj
Keyword(s):  
Aqueous Phase ◽  
Time Dependent ◽  
Absorption Bands ◽  
Decomposition Reactions ◽  
Maximum Extraction ◽  
The Stability ◽  
Kinetics Of ◽  
Alkali Salts ◽  
Nm Range

The extraction of dithiocarbamic acids with chloroform from aqueous phase containing their alkali salts has been investigated with regard to the fact that absorbing strongly in the 200-310 nm range, the acids interfere with the spectrophotometric determination of metals whose dithiocarbamate ligands exhibit their analytical absorption bands in that region. The amount of the dithiocarbamic acids formed depends on the kinetics of their formation and decomposition reactions and on the pH of the aqueous phase. The stability of the acids in chloroform extracts is highly time dependent. The maximum extraction of the acids (R2NCS2H) is attained at the following pH (R, pH): CH3 5.0, C2H5 5.9, C3H8 6.3, C4H9 6.8, C5H11 6.9, C6H13 6.9, iso-C3H7 7.2, iso-C4H9 6.9; for (CH3, iso-C3H7)NCS2H 7.3, C5H10NCS2H 7.2, C4H8ONCS2H 5.2.

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