First-principles calculation aided thermodynamic modeling of the Mo–Re system

Yang, Ying; Zhang, Chuan; Chen, Shuanglin; Morgan, Dane; Chang, Y. A.

doi:10.1016/j.intermet.2009.10.012

Cited by 15 publications

(10 citation statements)

References 26 publications

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“…At higher temperature, occupation of Np is lowered in groups II and IV while increased in groups I, III and V. In particular, DFT + U predicts that Np occupation increases strongly at higher temperature in group V. Overall, we expect that the ab initio predicted site occupations may provide some useful information for future thermodynamic description of ζ phase with a sublattice model, similar to combined ab initio and CALPHAD approach taken in Ref. [37] for the Mo-Re system. For example, group II and IV seem to show very similar composition and temperature dependence of occupation, suggesting they may be further grouped in a four-sublattice model without much loss of interesting physics.…”

Section: Ab Initio Predictions For ζ(Npu)mentioning

confidence: 60%

Ab initio energetics for modeling phase stability of the Np-U system

Xie

Chang

Morgan

2016

Journal of Nuclear Materials

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The Np-U system has been rarely studied despite this alloy being one key binary subsystem of metallic nuclear fuels. This study aims to further the understanding of the phase stability of the Np-U system through ab initio calculations. We first examined an existing CALPHAD model based on available experimental phase boundary data. We then focused on phases of which the CALPHAD model reproduces reasonably the experiment data and examined if values of the effective Hubbard U (i.e., U eff) parameter for Np and U fitted previously in the Np-Zr and U-Zr systems are also applicable to the Np-U system, using CALPHAD predicted enthalpies as references. We found that in general DFT + U predicts improved or at least similarly accurate enthalpies than standard DFT when the U eff 's used were within the ranges of single-structure optimized U eff 's (0.65-0.9 eV for Np and 1-1.5 eV for U)-for example, the multi-structure optimized U eff 's (0.9 eV for Np and 1.24 eV for U)-determined in previous U-Zr and Np-Zr studies. Finally, we focused on the intermediate phase ζ(Np,U), which at present is poorly characterized by experiments and unsatisfactorily described in the CALPHAD model. Based on ab initio calculated formation enthalpies for ordered end members and the compound energy formalism, we predicted its site occupations as function of compositions and temperature. Our study demonstrated that U eff 's fitted for U and Np determined in the U-Zr and Np-Zr systems may be transferable to the Np-U system and also provided new prediction of the site occupations for ζ(Np,U), which may serve as reference for future experimental and modeling study of the Np-U system.

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Section: Ab Initio Predictions For ζ(Npu)mentioning

confidence: 60%

Ab initio energetics for modeling phase stability of the Np-U system

Xie

Chang

Morgan

2016

Journal of Nuclear Materials

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“…Unlike the rather malleable Mo-rich alloys, their Re-rich counterparts turned out to be extremely hard. In addition, the Re 0.77 Mo 0.23 alloy resulted fragile after annealing at 1400 • C. Previously, the same arc-melting processes were adopted to cover the whole x range [42,43], with the samples being annealed at 1200 • C and then quenched in water. However, these early attempts failed to produce clean α-Mn phase.…”

Section: Methodsmentioning

confidence: 99%

“…By suitably combining arc melting and annealing processes, we could successfully synthesize pure-phase alloys representative of all four crystal structures. Although the Re 1−x Mo x phase diagram has been studied before, most of the obtained samples contained at least two different solid phases, thus preventing a systematic study of their physical properties [42,43]. Conforming to the binary phase diagram, the bcc-W and hcp-Mg solid phases were easily obtained via arc melting of Re and Mo and resulted to be stable at 1400 • C. Two reactions take place during the solidifying process: liquid → bcc-W + β-CrFe and liquid + hcp-Mg → β-CrFe.…”

Section: A Crystal Structuresmentioning

confidence: 99%

Structure and superconductivity in the binary Re1−xMox alloys

Shang

Gawryluk

Verezhak

et al. 2019

Phys. Rev. Materials

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The binary Re 1−x Mo x alloys, known to cover the full range of solid solutions, were successfully synthesized and their crystal structures and physical properties investigated via powder x-ray diffraction, electrical resistivity, magnetic susceptibility, and heat capacity. By varying the Re/Mo ratio, we explore the full Re 1−x Mo x binary phase diagram, in all its four different solid phases: hcp-Mg (P6 3 /mmc), α-Mn (I43m), β-CrFe (P4 2 /mnm), and bcc-W (Im3m), of which the second is noncentrosymmetric with the rest being centrosymmetric. All Re 1−x Mo x alloys are superconductors, whose critical temperatures exhibit a peculiar phase diagram, characterized by three different superconducting regions. In most alloys, the T c is almost an order of magnitude higher than in pure Re and Mo. Low-temperature electronic specific-heat data evidence a fully gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling across the series. Considering that several α-Mn-type ReT alloys (T = transition metal) show time-reversal symmetry breaking (TRSB) in the superconducting state, while TRS is preserved in the isostructural Mg 10 Ir 19 B 16 or Nb 0.5 Os 0.5 , the Re 1−x Mo x alloys represent another suitable system for studying the interplay of spaceinversion, gauge, and time-reversal symmetries in future experiments expected to probe TRSB in the ReT family.

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“…They found that the Monte Carlo species swaps allow for the equilibration of the structure, which cannot be achieved by conventional MD simulations [44]. In addition, the phenomenological CALculation of PHAse Diagrams (CALPHAD) approach [45] is proved to be an effective aid in materials design [46][47][48][49], and has recently been successfully used in the AlCoCrFeNi HEA system [50].…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

Tensile ductility of an AlCoCrFeNi multi-phase high-entropy alloy through hot isostatic pressing (HIP) and homogenization

Tang

Senkov

Parish

et al. 2015

Materials Science and Engineering: A

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The microstructure and phase composition of an AlCoCrFeNi high-entropy alloy (HEA) were studied in as-cast (AlCoCrFeNi-AC, AC represents as-cast) and homogenized (AlCoCrFeNi-HP, HP signifies hot isostatic pressed and homogenized) conditions. The AlCoCrFeNi-AC ally has a dendritrical structure in the consisting primarily of a nano-lamellar mixture of A2 [disorder body-centered-cubic (BCC)] and B2 (ordered BCC) phases, formed by an eutectic reaction. The homogenization heat treatment, consisting of hot isostatic pressed for 1 hour at 1,100 °C, 207 MPa and annealing at 1,150 °C for 50 hours, resulted in an increase in the volume fraction of the A1 phase and formation of a Sigma () phase. Tensile properties in ascast and homogenized conditions are reported at 700 °C. The ultimate tensile strength was virtually unaffected by heat treatment, and was 396 ± 4 MPa at 700 °C. However, 2 homogenization produced a noticeable increase in ductility. The AlCoCrFeNi-AC alloy showed a tensile elongation of only 1.0 %, while after the heat-treatment, the elongation of AlCoCrFeNi-HP was 11.7 %. Thermodynamic modeling of non-equilibrium and equilibrium phase diagrams for the AlCoCrFeNi HEA gave good agreement with the experimental observations of the phase contents in the AlCoCrFeNi-AC and AlCoCrFeNi-HP. The reasons for the improvement of ductility after the heat treatment and the crack initiation subjected to tensile loading were discussed.

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First-principles calculation aided thermodynamic modeling of the Mo–Re system

Cited by 15 publications

References 26 publications

Ab initio energetics for modeling phase stability of the Np-U system

Ab initio energetics for modeling phase stability of the Np-U system

Structure and superconductivity in the binary Re1−xMox alloys

Tensile ductility of an AlCoCrFeNi multi-phase high-entropy alloy through hot isostatic pressing (HIP) and homogenization

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