First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron

Satō, Kazunori; Shibutani, Yoji

doi:10.2320/matertrans.m2018014

Cited by 20 publications

(18 citation statements)

References 39 publications

(27 reference statements)

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“…The conclusion for Fe-C interaction is in good agreement with the findings from DFT calculations, showing the presence of C in BCC Fe forms local stress field and pushes the 1NN Fe atoms away to maintain the Fe-C equilibrium distance of 1.780 Å in ferromagnetic BCC. 14) For the C-C interaction, the result in this work is also consistent with the findings of Bhadeshia et al, 24) where it is stated that the closest approach distance of C atoms in BCC is 1.430 Å, corresponding to a highly repulsive energy. Finally, for C-V O and V Fe -C pairs, Fig.…”

Section: Atomic Pair Interaction Energysupporting

confidence: 91%

“…In BCC iron, it is well known that C atoms prefer to occupy the octahedral sites (O-sites) of BCC lattice. 14,15) For easy visualization, the structural model of Fe sites and O-sites in the BCC lattice are depicted in Fig. 1…”

Section: Cluster Expansion Methodsmentioning

confidence: 99%

“…In addition, the ferromagnetic state was considered because this is the ground state of the BCC Fe structure. 14)…”

Section: Total Energy Calculationsmentioning

confidence: 99%

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Atomic and Effective Pair Interactions in FeC Alloy with Point Defects: A Cluster Expansion Study

et al. 2019

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The Cluster Expansion Method (CEM) is used to investigate the pair interactions in body centered cubic (BCC) FeC alloy in the presence of vacancies. Within the CEM framework, the relation of cluster (point and pair) probabilities and set of independent correlation functions are derived. These are then applied to calculate the effective cluster interaction and atomic pair interaction energies for Fe, C and vacancy in FeC system. We found that, in this alloy, the interaction mostly comes from the first nearest neighbor pairs, and, to some degree, from the third nearest neighbor pairs. Detailed analysis shows that, within the first nearest neighbor pair interactions approximation, the C-C and Fe-C pair interactions are repulsive where the former one is more dominant. This is attributed to the local stress field formed in the vicinity of C atoms which pushes the first nearest neighbor atoms away to maintain the equilibrium distances. Moreover, there is an attractive interaction between C and vacancy which implies the possibility of C atoms to be trapped at vacancy site.From Eqs. (5) and (7), the point probabilities of the 4-constituent system above become: ..... (35) Here, J R α is not the same as the original J α in Eq. (29) but it is the linear combination of J α , obtained by replacing the linearly-dependent correlation functions ξ α with the linearly-independent ones. From the internal energies per lattice site in (34) and the correlation functions in matrix B, the effective cluster interaction energies (in eV) are calculated and listed below:

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Section: Atomic Pair Interaction Energysupporting

confidence: 91%

Section: Cluster Expansion Methodsmentioning

confidence: 99%

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Atomic and Effective Pair Interactions in FeC Alloy with Point Defects: A Cluster Expansion Study

et al. 2019

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“…All bonding states are found below the Fermi level (E F = 0 eV) and all antibonding states are found above the Fermi level, con rming covalent bonding characteristic between interstitial carbon and its neighboring Fe atoms. 38 Figure 5c compares the LDOS of interstitial carbon and Fe at the rst neighbor site with the total -pCOHP and orbital-resolved -pCOHP results between interstitial carbon and neighboring Fe atoms. We found the dominating bonding states around -12.5 eV to involve C 2s and Fe 4s orbitals (Figure 5c-iii) as expected from molecular orbital theory, 36,37 with a smaller contribution of C 2s -Fe 3d bonding (Figure 5c-iv), which is not observed in molecules.…”

Section: Effect Of Interstitial Carbon On Bond Strength Of An Alloy Smentioning

confidence: 99%

Understanding the Efficacy of Concentrated Interstitial Carbon in Enhancing the Pitting Corrosion Resistance of Stainless Steel

Chien

Ren

et al. 2021

Preprint

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By introducing a high fraction of interstitial carbon through low temperature carburization, the pitting corrosion resistance of austenitic stainless steel can be significantly improved. Previous work attributed this enhancement to the improvement of passive film properties. However, we show here that interstitial carbon actually weakens the passive film on stainless steel. In fact, the enhancement in pitting resistance is a result of carbon reducing the metal dissolution rate in a local pit environment by many orders of magnitude, which extremely decreases the growth stability of a pit and prevents it from transitioning into stable growth. Electronic structure calculations show that carbon bonds to the metal atoms and that the metal–carbon bonds are 1.6 to 2.0 times stronger than the metal–metal bonds. Different from prior theories, we show that the significant increase of pitting resistance originates from the formation of covalent bonds between interstitial carbon and its neighboring metal atoms, resulting in a significantly reduced dissolution rate. This study indicates a new strategy for the design of corrosion resistant alloys, namely alloying with concentrated interstitials that form strong bonds with the matrix atoms.

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“…In spite of very interesting magnetic properties, higher SPR and thermal stability, experimental reports on Fe 4 C are almost nonexistent and single-phase Fe 4 C has not yet been synthesized. Recently, interatomic potential for Fe-C systems were calculated using modified embedded atom method (MEAM) and it was predicted that the presence of C lowers the body center cubic (bcc) to face center cubic (fcc) transformation barrier [18,19]. Also the activation energy for C diffusion in Fe was calculated and found to be very small at about 0.8 eV [20].…”

Section: Introductionmentioning

confidence: 99%

Structural and magnetic properties of co-sputtered Fe0.8C0.2 thin films

Kumar

Reddy

Ganesan

et al. 2020

Phys. Rev. Materials

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We studied the structural and magnetic properties of Fe 0.8 C 0.2 thin films deposited by co-sputtering of Fe and C targets in a direct current magnetron sputtering (dcMS) process at a substrate temperature (T s ) of 300, 523, and 773 K. The structure and morphology were measured using x-ray diffraction (XRD), x-ray absorption nearedge spectroscopy (XANES) at Fe L and C K edges and atomic/magnetic force microscopy (AFM, MFM). An ultrathin (3-nm) 57 Fe 0.8C0.2 layer, placed between relatively thick Fe 0.8 C 0.2 layers was used to estimate Fe selfdiffusion taking place during growth at different T s using depth profiling measurements. Such 57 Fe 0.8C0.2 layer was also used for 57 Fe conversion electron Mössbauer spectroscopy (CEMS) and nuclear resonance scattering (NRS) measurements, yielding the magnetic structure of this ultrathin layer. We found from XRD measurements that the structure formed at low T s (300 K) is analogous to Fe-based amorphous alloy and at high T s (773 K), predominantly a Fe 3 C phase has been formed. Interestingly, at an intermediate T s (523 K), a clear presence of Fe 4 C (along with Fe 3 C and Fe) can be seen from the NRS spectra. The microstructure obtained from AFM images was found to be in agreement with XRD results. MFM results also agree well with NRS as the presence of multi-magnetic components can be clearly seen in the sample grown at T s = 523 K. The information about the hybridization between Fe and C, obtained from Fe L-and C K-edge XANES also supports the results obtained from other measurements. In essence, from this work, a possibility for experimental realization of Fe 4 C has been demonstrated. It can be anticipated that by further fine-tuning of the deposition conditions, even single-phase Fe 4 C can be realized which hitherto remains an experimental challenge.

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First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron

Cited by 20 publications

References 39 publications

Atomic and Effective Pair Interactions in FeC Alloy with Point Defects: A Cluster Expansion Study

Atomic and Effective Pair Interactions in FeC Alloy with Point Defects: A Cluster Expansion Study

Understanding the Efficacy of Concentrated Interstitial Carbon in Enhancing the Pitting Corrosion Resistance of Stainless Steel

Structural and magnetic properties of co-sputtered Fe0.8C0.2 thin films

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