Ferrite, martensite and supercritical iron: A coherent elastochemical theory of stress-induced carbon ordering in steel

Maugis, Philippe

doi:10.1016/j.actamat.2018.08.001

Cited by 20 publications

(33 citation statements)

References 34 publications

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“…This energy is minimum when the scalar product p O o r T : e is maximum. The case of uniaxial strain field along z, with i:: = (0, 0, i::o) is simple: (i) an O site verifies � > � (see Table 1 ), thus traction (i:: 0 > 0) favors 0 2 sites, while compression (i:: 0 < 0) equally favors Ox and O y sites compared to 0 2 • This is the origin of strain induced Zener ordering and inverse-Zener ordering (6,15]. (ii) On the contrary, a T site has PJ <PI: traction favors Tx and T y sites compared to T 2 , and the opposite for compression.…”

Section: Migration Under Fixed Strainmentioning

confidence: 99%

“…Thermodynamics of the Zener ordering in mechanically Ioaded bct-iron has been recently described within an elastochemical mean-field theory [6). The mode) is based on the continuum elas ticity theory of point defects coupled with the thermodynamics of dilute solid solutions.…”

Section: Order-disorder Transitionmentioning

confidence: 99%

“…The details can be found in Ref. [6). Distortion of the bec Iattice results in a Joss of crystal symmetry such that the octahedral and tetrahedral interstitial sites differen tiate into 3 sets each: Ox, O y , Oz and Tx, T y , Tz, also Iabelled O; and T;, i = 1, 2 or 3 ( Fig.…”

Section: Order-disorder Transitionmentioning

confidence: 99%

“…This is why ferrite and martensite pertain to the same "phase region" [5): they are two instances of bct-iron in the Fe-C-stress phase diagram. They differ only by their degree of long-range order: ferrite is the low order, low-tetragonality instance white martensite is the high order, high-tetragonality one [6).…”

Section: Introductionmentioning

confidence: 99%

“…Via modelling of the degree of ordering, ferrite and martensite are both treated in a coherent approach. Fe-C alloy thermodynamics is described by a mean-field elastochemical model based on the anisotropie elasticity theory of point defects and the dilute approximation of regular solutions (6). Carbon diffusivity is derived from the thermally activated jump frequencies by using the multisite method (23,24).…”

Section: Introductionmentioning

confidence: 99%

See 4 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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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: Migration Under Fixed Strainmentioning

confidence: 99%

Section: Order-disorder Transitionmentioning

confidence: 99%

Section: Order-disorder Transitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 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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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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Microstructure–Property Relationship in Cold-Drawn Pearlitic Steel Wires

Guelton

François

2020

Metall Mater Trans A

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Ferrite, martensite and supercritical iron: A coherent elastochemical theory of stress-induced carbon ordering in steel

Cited by 20 publications

References 34 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

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

Microstructure–Property Relationship in Cold-Drawn Pearlitic Steel Wires

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