DFT calculations of structural, magnetic and thermal properties of C15, C14 and C36 Laves phases in Fe-Nb-Zr

Rabahi, L.; Alili, B.; Bradai, Djamel; Grosdidier, Thierry; Kellou, A.

doi:10.1016/j.intermet.2016.12.011

Cited by 15 publications

(3 citation statements)

References 35 publications

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“…Our DFT calculation parameters are validated against previous calculations and experimental characterization of binary Laves phases c14 and c15 for both ZrFe 2 and NbFe 2 systems , (comparison is shown in the Supporting Information). Non-spin-polarized calculations were chosen to model NbFe 2 because the reference experiments were carried out at temperatures well above the Néel temperature of NbFe 2 (10K) . , …”

Section: Resultsmentioning

confidence: 56%

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

Kamath,

Long,

Aiyeru

et al. 2023

J. Phys. Chem. C

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Zirconium alloys have widespread applications in nuclear energy, with Zr-2.5Nb commonly being used as pressure tube material in reactors. Their microstructure encompasses intermetallic nanoprecipitates (NPs) and solutes that significantly impact their behavior in corrosive environments and irradiation. Hence, we analyze the crystal structure of Zr((Zr,) Nb,Fe)2 NPs using transmission electron microscopy (TEM), electronic density functional theory (DFT) calculations, and finite element analysis (FEA). Our findings unveil a mixed c14 and c15 Laves phase structure within the NPs and provide an explanation through the syncroshear mechanism. Through thermodynamic analysis, we evaluate the electronic, vibrational, and strain contributions to the free energy of the NPs. Our results indicate that the c15 structure is energetically favored at temperatures below 600 K, while the c14 structure prevails at higher temperatures. We provide an explanation for the observed coexistence of these structures in the NPs based on two key insights: (1) During annealing at high temperatures, the energetically favorable c14 NPs form, and (2) as the alloy cools, a partial phase transition to the c15 structure occurs, constrained by kinetic limitations. Furthermore, our study reveals that the NP/α-Zr interface is likely to be incoherent due to the considerable stresses involved. This finding is consistent with high-resolution transmission electron microscopy (HRTEM) micrographs, which demonstrate the presence of an incoherent interface.

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Section: Resultsmentioning

confidence: 56%

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

Kamath,

Long,

Aiyeru

et al. 2023

J. Phys. Chem. C

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“…Mössbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microanalysis [ 22 ] and the pseudo-potential density functional theory (PP-DFT) method [ 23 ] were used to study ternary Zr–Nb–Fe alloys corresponding in composition to the middle part of the equilibrium state diagram of the system. According to the results, it was concluded that Fe in the two Laves phases, present in the Zr–Nb–Fe system, forms two types of bcc of β-phases (Zr-enriched and Nb-rich).…”

Section: Introductionmentioning

confidence: 99%

Mössbauer and X-ray Studies of Radiation-Induced Processes in Nb–Zr Alloys Implanted with 57Fe Ions

2023

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The effect of implanting 57Fe ions on the crystal structure of Nb–Zr alloys has been studied using Mössbauer spectroscopy on 57Fe nuclei and X-ray diffraction. As a result of implantation, a metastable structure was formed in the Nb–Zr alloy. The XRD data indicated a decrease in the crystal lattice parameter of niobium; that is, there was a compression of the niobium planes when implanted with iron ions. Mössbauer spectroscopy revealed three states of iron. The singlet indicated a supersaturated Nb(Fe) solid solution; the doublets characterized the diffusion migration of atomic planes and crystallization of voids. It was shown that the values of the isomer shifts in all three states did not depend on the implantation energy, which indicates the invariance of the electron density on the 57Fe nuclei in the studied samples. The resonance lines of the Mössbauer spectra were significantly broadened, which is typical for materials with low crystallinity and a metastable structure that is stable at room temperature. The paper discusses the mechanism of radiation-induced and thermal transformations in the Nb–Zr alloy, which leads to the formation of a stable well-crystallized structure. A Fe2Nb intermetallic compound and the Nb(Fe) solid solution formed in its near-surface layer, while Nb(Zr) remained in the bulk.

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“…Magnetic properties of the hexagonal C14 Laves phase NbFe 2 have been subject of numerous experimental [1][2][3][4][5][6][7][8][9][10][11][12] and theoretical [13][14][15][16][17] studies. The interest in the system follows from the fact that its magnetic state turned out to be very delicate and it can be easily impaired by external magnetic field H > 6 kOe or by slight deviation from the stoichiometry.…”

Section: Introductionmentioning

confidence: 99%

On the magnetism of C14 Nb(Fe_89.4Al_10.6)₂ Laves phase intermetallic compound

Dubiel¹,

Felner²

2019

EPL

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C14 Nb (Fe 89.4 Al 10.6 ) 2 Laves phase intermetallic compound was investigated by DC magnetization (M) measurements performed in the temperature (T) interval of 20 to 175 K,under an applied magnetic field (H) ranging between 50 and 1250 Oe.Magnetization curves were recorded in the field-cooled (FC) and in the zero-fieldcooled (ZFC) modes. They clearly showed an irreversible character that vanished at H=1250 Oe. Both magnetization curves exhibited well-defined peaks around T N =72.3 K whose positions were H-independent, so they were identified as the compound's Néel temperature. The existence of irreversibility which decreases with H testify to a re-entrant character of magnetism in the studied compound. An increase of both M FC and M ZFC observed below T N likely indicates a mixed i.e. ferromagnetic and antiferromagnetic ground magnetic state of the studied system. * Corresponding author: Stanislaw.Dubiel@fis.agh.edu.pl (S. M. Dubiel)

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DFT calculations of structural, magnetic and thermal properties of C15, C14 and C36 Laves phases in Fe-Nb-Zr

Cited by 15 publications

References 35 publications

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

Mössbauer and X-ray Studies of Radiation-Induced Processes in Nb–Zr Alloys Implanted with 57Fe Ions

On the magnetism of C14 Nb(Fe_89.4Al_10.6)₂ Laves phase intermetallic compound

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DFT calculations of structural, magnetic and thermal properties of C15, C14 and C36 Laves phases in Fe-Nb-Zr

Cited by 15 publications

References 35 publications

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)2 Nanoprecipitates in Zr-2.5Nb

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)2 Nanoprecipitates in Zr-2.5Nb

Mössbauer and X-ray Studies of Radiation-Induced Processes in Nb–Zr Alloys Implanted with 57Fe Ions

On the magnetism of C14 Nb(Fe89.4Al10.6)2 Laves phase intermetallic compound

Contact Info

Product

Resources

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Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

Solid-State Phase Transformation Explains the Mixed Crystallographic Character of Zr(Nb,Fe)₂ Nanoprecipitates in Zr-2.5Nb

On the magnetism of C14 Nb(Fe_89.4Al_10.6)₂ Laves phase intermetallic compound