Effect of alloying on the self-diffusion activation energy in γ-iron

Vasilyev, A.; Sokolov, S. F.; Колбасников, Н. Г.; Sokolov, D. F.

doi:10.1134/s1063783411110308

Cited by 64 publications

(30 citation statements)

References 7 publications

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“…These values of material constants and activation energy are closer to the reported values of similar kind of hot deformed steels [22][23][24]. Due to the effect of alloying elements, the apparent activation energy for hot deformation (456.42 kJmol −1 ) of present steel is much larger than the self-diffusion activation energy of austenitic steel i.e 312 kJmol −1 [25,26].…”

Section: Determination Of Materials Constants and Activation Energysupporting

confidence: 84%

Critical condition parameters and kinetics of dynamic recrystallization for hot deformed 1 wt%Cr-1 wt%Mo rotor steel

Kumar

Nath

2020

Mater. Res. Express

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Isothermal hot compression tests of low alloy 1 wt%Cr-1 wt%Mo medium carbon rotor steel were carried out over the temperature range from 850°C-1050°C under three strain rates e ( )  varying from 0.001 s −1 -0.1 .1 s −1 . The hot deformation behavior, activation energy and material constants were determined by constitutive analysis. Onset of critical condition parameters for dynamic recrystallization (DRX) of the present steel were determined with the help of mathematical models developed by Poliak and Jonas. DRX kinetics were studied to determine the fraction of dynamic recrystallization with the help of Avrami type model. Also, the values of Avrami power exponent n ( ) and material constant K ( )were calculated for Avrami equation in each deformation condition. Optical and scanning electron (SEM) micrographs of the as-received and the deformed specimens were analyzed to understand the flow stress behavior of this steel.

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Section: Determination Of Materials Constants and Activation Energysupporting

confidence: 84%

Critical condition parameters and kinetics of dynamic recrystallization for hot deformed 1 wt%Cr-1 wt%Mo rotor steel

Kumar

Nath

2020

Mater. Res. Express

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“…The activation energies for self-diffusion in pure iron with fcc and bcc structures are ~278 kJ/mol [36] and ~255 kJ/mol [37,38], respectively, and the activation energies for diffusion along grain boundaries and dislocations are about one-half of the value for selfdiffusion in coarse-grained materials [39,40]. Thus, the activation energy for grain boundary and bulk diffusion of iron in Fe-20Cr-25Ni-Nb stainless steel is ~178 and ~278 kJ/mol, respectively [41] and the activation energy for grain boundary diffusion of iron in 316 stainless steels is ~173 kJ/mol [42].…”

Section: Correlation Between the Microstructure And The Activation Enmentioning

confidence: 99%

“…This difference is attributed to the lower frequency of diffusion short circuits in the sample processed by ¼ turn due to the inherent larger grain size and the smaller dislocation density. In addition, the higher fraction of γ-austenite after ¼ turn may also contribute to the higher activation energy of recovery since diffusion in the fcc iron structure is more difficult than in the bcc phase as shown by the higher self-diffusion activation energy [36][37][38].…”

Section: Correlation Between the Microstructure And The Activation Enmentioning

confidence: 99%

High temperature thermal stability of nanocrystalline 316L stainless steel processed by high-pressure torsion

El-Tahawy

Huang

Choi

et al. 2017

Materials Science and Engineering: A

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Differential scanning calorimetry (DSC) was used to study the thermal stability of the microstructure and the phase composition in nanocrystalline 316L stainless steel processed by high-pressure torsion (HPT) for ¼ and 10 turns. The DSC thermograms showed two characteristic peaks which were investigated by examining the dislocation densities, grain sizes and phase compositions after annealing at different temperatures. The first DSC peak was exothermic and was related to recovery of the dislocation structure without changing the phase composition and grain size. The activation energies for recovery after processing by ¼ and 10 turns were ~163 and ~106 kJ mol -1 , respectively, suggesting control by diffusion along grain boundaries and dislocations. The second DSC peak was endothermic and was caused by a reverse transformation of α'-martensite to γ-austenite. The hardness of annealed samples was determined primarily by the grain size and followed the Hall-Petch relationship.Nanocrystalline 316L steel processed by HPT exhibited good thermal stability with a grain size of ~200 nm after annealing at 1000 K and a very high hardness of ~4900 MPa.

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“…According to the physics of diffusional rearrangements of atoms during the boundary migration of growing grains, the related activation energy should be comparable with the activation energy of grain boundary self-diffusion that, in turn, correlates with a similar characteristic for the bulk selfdiffusion (activation energy of self-diffusion, AESD), which is higher by about two times. It is notable that known results obtained by the radioactive tracer technique, which have been compiled by the authors [24], undoubtedly indicate that AESD in solid solutions of austenite depends on their chemical compositions. An empirical expression proposed in the last quoted paper enables accurate calculation of AESD in terms of quantities of alloying elements (С, Mn, Si, Ni, Cr, Mo, Nb, V, Ti) most important for up-to-date steels.…”

Section: Introductionmentioning

confidence: 91%

Modeling of grain growth kinetics in complexly alloyed austenite

Vasilyev

Sokolov

et al. 2019

Lett. Mater.

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A quantitative model is presented to describe the kinetics of grain growth in complexly alloyed austenite. The model assumes that the activation energy of grain growth is proportional to the activation energy of bulk self-diffusion, which is calculated as a function of the chemical composition of the solid solution using the previously obtained formula. The empirical parameters of the model are determined on the basis of experimental data on the kinetics of isothermal grain growth in steels with the chemical composition varying in a wide range: C (0.05 ÷ 0.32), Mn (0.30 ÷1.88), Si (0.01÷ 0.29), Ni (0.0 ÷ 4.0), Cr (0.0 ÷ 2.0), Mo (0.0 ÷ 0.5), Nb (0.00 ÷ 0.05) available in the literature. The model allows one to obtain good agreement with the experiment for the considered steels in which the minimum (~ 79.7 kJ / mol) and maximum (~ 243.7 kJ / mol) values of the activation energy of grain growth differ by 3 times. The average absolute value of the relative error in calculating the grain size is about 11 % that is comparable to the measurement error. Taking into account the influence of the chemical composition on the activation energy of grain growth, implemented in the developed model, it is possible to obtain agreement with the experiment without accounting for the solid-solution pinning of moving boundaries (the solute drag effect) requires a large number of additional empirical parameters (two exponential parameters for each alloying element). This result deserves further consideration from the physical viewpoint and verification on both simple carbon steels and steels with various quantities of Mn, Mo and Nb, which, according to literature, exert the strongest solute drag effect.

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Effect of alloying on the self-diffusion activation energy in γ-iron

Cited by 64 publications

References 7 publications

Critical condition parameters and kinetics of dynamic recrystallization for hot deformed 1 wt%Cr-1 wt%Mo rotor steel

Critical condition parameters and kinetics of dynamic recrystallization for hot deformed 1 wt%Cr-1 wt%Mo rotor steel

High temperature thermal stability of nanocrystalline 316L stainless steel processed by high-pressure torsion

Modeling of grain growth kinetics in complexly alloyed austenite

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