Diffusion Behavior of Carbon Atoms in Austenite Region of SCM435 Steel

2016 ◽  
Vol 850 ◽  
pp. 266-270 ◽  
Author(s):  
Dong Xu ◽  
Bing Zheng ◽  
Xing Liang Gao ◽  
Miao Yong Zhu
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Arrhenius Equation ◽  
Diffusion Constant ◽  
Carbon Diffusion ◽  
Diffusion Activation Energy ◽  
Diffusion Behavior ◽  
Scm435 Steel ◽  
The Relationship ◽  
Diffusion Activation

The research on the decarbonizing behavior of the austenite region of SCM435 steel was carried out. And the experimental results shewed that the relationship between the diffusion coefficient and temperature totally agreed with the Arrhenius equation and that the diffusion constant and the diffusion activation energy were uniform within the temperature range of 900-1100°C. However, when the austenite reached certain temperature, the carbon diffusion coefficient decreased significantly as temperature increased and its relationship with temperature no longer agreed with the Arrhenius equation.

scholarly journals Ternary interdiffusion coefficients in α2-phase Ti3Al/Nb system

2012 ◽  
Vol 48 (2) ◽  
pp. 283-290 ◽  
Author(s):  
W. Wang ◽  
B. Yuan ◽  
C. Zhou
Keyword(s):  
Activation Energy ◽  
Ternary System ◽  
Diffusion Coefficients ◽  
Theoretical Basis ◽  
Single Phase ◽  
Arrhenius Equation ◽  
Diffusion Activation Energy ◽  
Α2 Phase ◽  
Interdiffusion Coefficients ◽  
Diffusion Activation

The ?2 single phase interdiffusion in Ti3Al-Nb ternary system was studied at temperatures of 1323, 1373 and 1423 K. The interdiffusion coefficients were calculated by the method of Dayananda. The average ternary interdiffusion coeffcients were determined in the mid of the diffusion zone, and the trace diffusion coefficients can be estimitaed in the limit cX?0. The obtained main interdiffusion coeffcients is little smaller than privious reported and the diffusion activation energy of Nb calculated by the trace diffusion coefficients is 299.29 kJmol-1 accoding to the Arrhenius equation. These results can provide a theoretical basis for the mechanisms of Nb improving the oxidation resistance of Ti3Al.

Size-Dependent Diffusion Coefficient in Nanocrystalline Materials

2011 ◽  
Vol 391-392 ◽  
pp. 418-421 ◽  
Author(s):  
S. Zhang
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Simple Model ◽  
Model Prediction ◽  
Nanocrystalline Materials ◽  
Free Parameter ◽  
Room Temperature ◽  
Diffusion Activation Energy ◽  
Size Dependent ◽  
Diffusion Activation

A simple model, without any free parameter, is introduced to predict the size-dependent diffusion coefficient of nanocrystalline materials in this contribution. It is found that as the size of the nanocrystals decreases, the diffusion activation energy of atoms decreases and the corresponding diffusion coefficient strongly increases due to the Arrhenius relationship between them, which leads to evident diffusion at the room temperature. The model prediction is in agreement with the experimental diffusion results of Cu and Ag diffusion in Cu nanocrystalline materials.

scholarly journals Thermally stimulated oxygen desorption in Sr2FeMoO6-δ

2018 ◽  
Vol 4 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Nikolay A. Kalanda
Keyword(s):  
Activation Energy ◽  
Oxygen Diffusion ◽  
Gas Flow ◽  
Oxygen Vacancies ◽  
Early Stage ◽  
Diffusion Activation Energy ◽  
Energy Calculation ◽  
Heating Rates ◽  
Oxygen Desorption ◽  
Diffusion Activation

Polycrystalline Sr2FeMoO6-δ specimens have been obtained by solid state synthesis from partially reduced SrFeO2,52 and SrMoO4 precursors. It has been shown that during oxygen desorption from the Sr2FeMoO6-δ compound in polythermal mode in a 5%H2/Ar gas flow at different heating rates, the oxygen index 6-δ depends on the heating rate and does not achieve saturation at T = 1420 K. Oxygen diffusion activation energy calculation using the Merzhanov method has shown that at an early stage of oxygen desorption from the Sr2FeMoO6-δ compound the oxygen diffusion activation energy is the lowest Еа = 76.7 kJ/mole at δ = 0.005. With an increase in the concentration of oxygen vacancies, the oxygen diffusion activation energy grows to Еа = 156.3 kJ/mole at δ = 0.06. It has been found that the dδ/dt = f (Т) and dδ/dt = f (δ) functions have a typical break which allows one to divide oxygen desorption in two process stages. It is hypothesized that an increase in the concentration of oxygen vacancies Vo•• leads to their mutual interaction followed by ordering in the Fe/Mo-01 crystallographic planes with the formation of various types of associations.

Te Induced AlAs/GaAs Superlattice Mixing

1988 ◽  
Vol 126 ◽  
Author(s):  
P. Mel ◽  
S. A. Schwarz ◽  
T. Venkatesan ◽  
C. L. Schwartz ◽  
E. Colas
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Diffusion Coefficient ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Secondary Ion Mass Spectrometry ◽  
Chemical Vapor ◽  
Temperature Range ◽  
The Relationship ◽  
Secondary Ion

ABSTRACTTe enhanced mixing of AlAs/GaAs superlattice has been observed by secondary ion mass spectrometry. The superlattice sample was grown by organometallic chemical vapor deposition and doped with Te at concentrations of 2×1017 to 5×1018 cm−.3 In the temperature range from 700 to 1000 C, a single activation energy for the Al diffusion of 2.9 eV was observed. Furthermore, it has been found that the relationship between the Al diffusion coefficient and Te concentration is linear. Comparisons have been made between Si and Te induced superlattice mixing.

Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiang Qiu ◽  
Kun Zhang ◽  
Qin Kang ◽  
Yicheng Fan ◽  
Hongyu San ◽  
...  
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Hydrogen Atom ◽  
Hydrogen Embrittlement ◽  
First Principles ◽  
Hydrogen Diffusion ◽  
First Principles Calculations ◽  
Content Type ◽  
Diffusion Behavior ◽  
Hydrogen Diffusion Coefficient

Purpose This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage. Design/methodology/approach The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects. Findings The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe. Originality/value This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

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