Temperature hysteresis of the order-disorder transition in carbon-supersaturated α-Fe

Maugis, Philippe; Danoix, F.; Zapolsky, H.; Cazottes, Sophie; Gouné, Mohamed

doi:10.1103/physrevb.96.214104

Cited by 21 publications

(17 citation statements)

References 24 publications

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“…-The material parameters (dipole tensor, stiffness tensor) are composition-and temperature-independent in the range of (a) 0-10 at.% C and 0-1000 K. This hypothesis of homogeneous elasticity is correct within an accuracy of about 10% [25,26); -Hillert's [22) assumption that the strain induced by the popu lation of carbon atoms is uniform in the crystal (the mean-field approximation). This was confirmed by previous studies [27,28].…”

Section: Order-disorder Transitionsupporting

confidence: 92%

“…3).Using the data of Zener[3], Hillert approximated the change in activation energy to E H z = 3.11 eV per unit carbon fraction. From our model, we find E H z = 1.82 eV with our materials data [Eq (28)…”

supporting

confidence: 70%

“…Eqs. (28) and (29) agree that the migration enthalpy H 12 is the lowest of the three, i.e. the jumps from disfavored to favored sites are the most probable in stress-free martensite.…”

Section: Discussionmentioning

confidence: 68%

“…From Eq. 11, the corresponding variations in migration enthalpies H i i -Hg1 are Mf12 = -3.81c t:..Hn = +3.77c t.H3 1 = + 1.82c (28) with Hg1 = 0.872 eV. On their side, by molecular dynamics with EAM potential coupled to kinetic Monte Carlo, Lawrence et al [27] found t.H 1 2 = -1.87xc t:..Hn = -1.17xc t.H3 1 = + 1.13xc (29) with Hg1 = 0.815 eV and X e = c/(1 + c).…”

Section: Discussionmentioning

confidence: 98%

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Stress-controlled carbon diffusion channeling in bct-iron: A mean-field theory

Maugis¹,

Chentouf²,

Connétable³

2018

Journal of Alloys and Compounds

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Diffusion of interstitial carbon atoms in iron is the rate-limiting phenomenon of a number of phase transitions in body-centered (bec) and body-centered tetragonal (bct) phases such as ferrite and martensite. These phases being rarely stress-free and undeformed, the influence of stress/strain on the diffusivity of carbon is essential, although scarcely documented. We developed a model of carbon elastodiffusion in bct-iron. We combined anisotropie linear elasticity theory of point defects, the dilute approximation of regular solutions and the multisite model of random walk into a coherent mean-field theory. The model allows predicting the effects of composition, temperature and mechanical loading on the anisotropy of carbon diffusion. Density functional theory calculations have provided most of the materials parameters. The predictions were successfully tested against kinetic Monte Carlo simulations. Our results show that compression of the crystal increases carbon diffusivity, while tension has the opposite effect. Axial straining is accompanied by a large anisotropy of diffusion. This effect could be exploited to produce stress-controlled diffusion channeling for the engineering of anisotropie micro structures during thermal ageing of martensitic Fe-C alloys.

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Section: Order-disorder Transitionsupporting

confidence: 92%

supporting

confidence: 70%

“…Eqs. (28) and (29) agree that the migration enthalpy H 12 is the lowest of the three, i.e. the jumps from disfavored to favored sites are the most probable in stress-free martensite.…”

Section: Discussionmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 98%

See 2 more Smart Citations

Stress-controlled carbon diffusion channeling in bct-iron: A mean-field theory

Maugis¹,

Chentouf²,

Connétable³

2018

Journal of Alloys and Compounds

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“…If in phase transitions involving crystalline phases, appropriate order parameters can be unambiguously defined e.g. [20], [21], there is no consensus on which structural order parameter should be adopted to best represent the configurational state of a vitrifying liquid/glass. Hole theory of liquids has a long history since the pioneering works of Eyring [22] and Frenkel [23].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic analysis of the classical lattice-hole model of liquids

Benigni

2020

Journal of Non-Crystalline Solids

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A complete thermodynamic analysis of the classical 2-parameter lattice-hole model of liquids is presented. To our knowledge, no such analysis was available before. It is shown that the model depicts a van der Waals like behavior. The calculated phase diagram features a coexistence line between a condensed and a gas phases ending at a critical point. The model is not able to describe a transition between two condensed phases such as melting. Model parametrization to simulate an archetypal fragile glass forming liquid, the ortho-terphenyl, reveals an only qualitative/semi-quantitative agreement with available experimental information. The extreme simplicity of this 2-parameter model restricts its ability to describe a real liquid. Taking into account the existence of a volume difference between a hole and a molecule, inserting a temperature and pressure dependencies of the physical parameters and allowing the energy parameter to depend on the hole concentration are the most promising modeling options.

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A theory of Snoek relaxation in iron-carbon bct-martensite

Maugis

2022

J Mater Sci

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Martensite is a major constituent of Fe-C alloys. Its metastable body-centered tetragonal structure provides high tensile strength to martensitic steels. Recent experiments highlighted the benefit of large solute carbon content to the strength and ductility of the so-called virgin martensite obtained by sub-zero quench. The results suggest a significant contribution of the elastic and anelastic deformation of the martensite crystals to the rheology of these alloys. In order to shed light on the influence of carbon content on the anelastic response, we investigated theoretically the behavior of solute carbon during Snoek relaxation. Thanks to a linear-response approach, we obtained analytical formulae of the atomic mobilities and the thermodynamic affinities, from which the relaxation strength and time were derived. We unravel the unexpected decrease of the relaxation strength and time when solute carbon content is increased. Relaxation kinetics is explained at the atomic scale by an indirect mechanism of carbon migration in martensite, at variance with ferrite. We emphasize the onset of non-linear effects when the applied stress is high.

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Temperature hysteresis of the order-disorder transition in carbon-supersaturated α-Fe

Cited by 21 publications

References 24 publications

Stress-controlled carbon diffusion channeling in bct-iron: A mean-field theory

Stress-controlled carbon diffusion channeling in bct-iron: A mean-field theory

Thermodynamic analysis of the classical lattice-hole model of liquids

A theory of Snoek relaxation in iron-carbon bct-martensite

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