Configurational thermodynamics of C in body-centered cubic/tetragonal Fe: A combined computational study

Yan, Jia-Yi; Ruban, Andrei V.

doi:10.1016/j.commatsci.2018.02.024

Cited by 17 publications

(21 citation statements)

References 39 publications

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“…This value is relatively close to the activation enthalpy of the present work t:..H 13 /c = 3.77 eV, suggesting that diffusion in the axial direction is the limiting mechanism for spinodal decomposition. This is in accordance with the recent theoretical investigation of Yan et al [15), who exhibited decomposition of martensite into a modu lated structure of wave vector [O O fol parallel to the applied strain, hence necessitating diffusion in the axial direction.…”

Section: Discussionsupporting

confidence: 92%

“…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%

“…Various models of order-disorder transition during low temperature ageing [7][8][9][10][11] or severe plastic deformation [12,13) have been proposed in the literature. Sorne of them include the effect of particular mechanical loadings [7,14,15). None includes a comprehensive study of the effects of tensile and compressive stress, neither do they fully treat the ferrite -martensite ordering transition under applied stress.…”

Section: Introductionmentioning

confidence: 99%

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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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: Discussionsupporting

confidence: 92%

Section: Migration Under Fixed Strainmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…On the theoretical side, investigations of carbon ordering in iron involved various techniques: thermodynamic meanfield modelling [12,13,14,15,16], the microscopic elasticity theory [4,10,17,18,19], the CALPHAD formalism [20,21], molecular dynamics [22,23,14,24] and combined ab initio-Monte Carlo [25,26,16,27]. Most of these approaches, although based on di erent hypotheses and approximations, provide results in favour of Zener ordering.…”

mentioning

confidence: 99%

“…Most of these approaches, although based on di erent hypotheses and approximations, provide results in favour of Zener ordering. One exception is the work of Ruban [25,26], which predicts an "anti-Zener" ordering consisting of carbon atoms occupying specific sites on two preferred octahedral sublattices, associated with a ratio c_a < 1. The relative stability of this configuration, as compared to Zener order, is explained by the asserted dominating e ect of carbon-carbon short-range interactions.…”

mentioning

confidence: 99%

Stability of Zener order in martensite: an atomistic evidence

Maugis

Connétable²,

Eyméoud³

2021

Scripta Materialia

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Martensite is a supersaturated solid solution of carbon in body-centered iron wherein interstitial carbon atoms preferentially occupy a single octahedral sublattice. Despite a century of research, the mechanism of this long-range ordering is still a subject of debate. Recently, Zener's theory of ordering was challenged both experimentally and theoretically. In an attempt to settle the controversy, we investigated by density functional theory the ground states of Fe-C configurations having various degrees of order. We conclude that the fully Zener-ordered configurations are always the most stable, thus confirming Zener's theory. Comparison with mean-field elasticity and Ising-type modelling supports the elastic origin of Zener ordering.

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A Temperature–Stress Phase Diagram of Carbon-Supersaturated bcc-Iron, Exhibiting “Beyond-Zener” Ordering

Maugis

2020

J. Phase Equilib. Diffus.

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Carbon ordering in supersaturated body-centered iron was investigated by means of atomic-scale simulations. Beyond the well-known Zener ordering of carbon atoms, our results reveal a first-order transition occurring upon temperature change when a single crystal is subjected to axial compression. This ordering produces orthorhombic martensite due to unequal carbon redistribution over the three octahedral interstitial sites. The resulting phase diagram is of the rare homotectoid type. Connection is made with the thermoelastic behavior of martensitic alloys, which proves to be similar to that of shape-memory alloys.

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Configurational thermodynamics of C in body-centered cubic/tetragonal Fe: A combined computational study

Cited by 17 publications

References 39 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

Stability of Zener order in martensite: an atomistic evidence

A Temperature–Stress Phase Diagram of Carbon-Supersaturated bcc-Iron, Exhibiting “Beyond-Zener” Ordering

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