X-ray analysis of diffusion controlled phase transformation kinetics

1972 ◽  
Vol 3 (7) ◽  
pp. 1999-2000
Author(s):  
W. H. Halsted ◽  
J. E. Gragg
Keyword(s):  
Phase Transformation ◽  
Transformation Kinetics ◽  
X Ray ◽  
Phase Transformation Kinetics ◽  
Diffusion Controlled

scholarly journals Study on the Phase Transformation Kinetics of Sol-Gel DrivedTiO2Nanoparticles

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
H. Mehranpour ◽  
M. Askari ◽  
M. Sasani Ghamsari ◽  
H. Farzalibeik
Keyword(s):  
Activation Energy ◽  
Phase Transformation ◽  
Sol Gel ◽  
Rutile Phase ◽  
Transformation Kinetics ◽  
X Ray ◽  
Prepared Nanoparticles ◽  
Phase Transformation Kinetics ◽  
Diffusion Controlled ◽  
Kinetics Of

Titanium dioxide nanopowders were synthesized by the diffusion controlled sol-gel process (LaMer model) and characterized by DTA-TG, XRD, and SEM. The preparedTiO2nanoparticles have uniform size and morphology, and the phase transformation kinetics of obtained material was studied by interpretation of the X-ray diffraction patterns peaks on the base of Avrami equation. The stating point of anatase-rutile phase transformation temperature in the prepared nanoparticles was found between 100 and200°C. A decreasing trend on the intensity of X-ray peaks of anatase phase was observed up to600°Cwhen the presence of the rutile phase became predominant. Results indicated that the transition kinetics of the diffusion controlled prepared nanoparticles was begun at low temperature, and it can be concluded that the nucleation and growth sites in these particles were more than other. However, it has been found that the nucleation activation energy of rutile phase was 20 kj/mol, and it is the lowest reported activation energy.

scholarly journals Phase Transformation Kinetics of a FCC Al0.25CoCrFeNi High-Entropy Alloy during Isochronal Heating

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1015
Author(s):  
Jun Wang ◽  
Chen Wei ◽  
Haoxue Yang ◽  
Tong Guo ◽  
Tingting Xu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Phase Transformation ◽  
High Entropy Alloy ◽  
Transformation Kinetics ◽  
High Entropy ◽  
Phase Transformation Kinetics ◽  
Diffusion Controlled ◽  
Thermal Dilation ◽  
Kinetics Of

The phase transformation kinetics of a face-centered-cubic (FCC) Al0.25CoCrFeNi high-entropy alloy during isochronal heating is investigated by thermal dilation experiment. The phase transformed volume fraction is determined from the thermal expansion curve, and results show that the phase transition is controlled by diffusion controlled nucleation-growth mechanism. The kinetic parameters, activation energy and kinetic exponent are determined based on Kissinger–Akahira–Sunose (KAS) and Johnson–Mehl–Avrami (JMA) method, respectively. The activation energy and kinetic exponent determined are almost constant, indicating a stable and slow speed of phase transition in the FCC Al0.25CoCrFeNi high-entropy alloy. During the main transformation process, the kinetic exponent shows that the phase transition is diffusion controlled process without nucleation during the transformation.

scholarly journals In Situ Analysis of the Phase Transformation Kinetics in the β-Water-Quenched Ti-5Al-5Mo-5V-3Cr-1Zr Alloy during Ageing after Fast Heating

2020 ◽  
Vol 4 (1) ◽  
pp. 12
Author(s):  
Rafael Paiotti Marcondes Guimarães ◽  
Bruna Callegari ◽  
Fernando Warchomicka ◽  
Katherine Aristizabal ◽  
Flavio Soldera ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Energy ◽  
Transformation Kinetics ◽  
X Ray Diffraction ◽  
Fast Heating ◽  
X Ray ◽  
Β Phase ◽  
Phase Transformation Kinetics ◽  
Structural Applications

Thermal treatments are the main route to achieve improvements in mechanical properties of β-metastable titanium alloys developed for structural applications in automotive and aerospace industries. Therefore, it is of vital importance to determine phase transformation kinetics and mechanisms of nucleation and precipitation during heat treatment of these alloys. In this context, the present paper focuses on the assessment of solid-state transformations in a β-water-quenched Ti-5Al-5Mo-5V-3Cr-1Zr alloy during the early stages of ageing treatment at 500 °C. In situ tracking of transformations was performed using high-energy synchrotron X-ray diffraction. The transformation sequence β + ω → α + α”iso + β is proposed to take place during this stage. Results show that isothermal α” phase precipitates from ω and from spinodal decomposition domains of the β phase, whereas α nucleates from ω, β and also from α” with different morphologies. Isothermal α” is considered to be the regulator of transformation kinetics. Hardness measurements confirm the presence of ω, although this phase was not detected by X-ray diffraction during the in situ treatment.

scholarly journals Solid state phase transformation kinetics in Zr-base alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. R. Massih ◽  
Lars O. Jernkvist
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Zirconium Alloys ◽  
Excess Oxygen ◽  
Transformation Kinetics ◽  
Fuel Cladding ◽  
Reactor Accident ◽  
Phase Transformation Kinetics ◽  
Solid State Phase Transformation ◽  
Water Reactors

AbstractWe present a kinetic model for solid state phase transformation ($$\alpha \rightleftharpoons \beta$$ α ⇌ β ) of common zirconium alloys used as fuel cladding material in light water reactors. The model computes the relative amounts of $$\beta$$ β or $$\alpha$$ α phase fraction as a function of time or temperature in the alloys. The model accounts for the influence of excess oxygen (due to oxidation) and hydrogen concentration (due to hydrogen pickup) on phase transformation kinetics. Two variants of the model denoted by A and B are presented. Model A is suitable for simulation of laboratory experiments in which the heating/cooling rate is constant and is prescribed. Model B is more generic. We compare the results of our model computations, for both A and B variants, with accessible experimental data reported in the literature covering heating/cooling rates of up to 100 K/s. The results of our comparison are satisfactory, especially for model A. Our model B is intended for implementation in fuel rod behavior computer programs, applicable to a reactor accident situation, in which the Zr-based fuel cladding may go through $$\alpha \rightleftharpoons \beta$$ α ⇌ β phase transformation.

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