| 1. |
- Li, Xiaojie, et al.
(författare)
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First-principles study of crystal-face specificity in surface properties of Fe-rich Fe-Cr alloys
- 2019
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Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- A density-functional theory investigation of the (100) and (110) surfaces of the body-centered cubic (bcc) Fe1-xbCrxb binary alloys, x(b) <= 15 at.%, is reported. The energies and segregation energies of these surfaces were calculated for chemically homogeneous concentration profiles and for Cr surface contents deviating from the nominal one of the bulk. The implications of these results for the surface alloy phase diagram are discussed. The surface chemistry of Fe-Cr(100) is characterized by a transition from Cr depletion to Cr enrichment in a critical bulk Cr composition window of 6 < x(b) < 9 at.%. In contrast, such threshold behavior of the surface Cr content is absent for Fe-Cr(110) and a nearly homogeneous Cr concentration profile is energetically favorable. The strongly suppressed surface-layer relaxation at both surfaces is shown to be of magnetic origin. The compressive, magnetic contribution to the surface relaxation stress is found to correlate well with the surface magnetic moment squared at both surface terminations. The stability of the Cr surface magnetic moments against bulk Cr content is clarified based on the surface electronic structure.
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| 2. |
- Zhao, W., et al.
(författare)
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Thermo-mechanical properties of Ni-Mo solid solutions : A first-principles study
- 2019
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Ingår i: Computational materials science. - : Elsevier B.V.. - 0927-0256 .- 1879-0801. ; 158, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical strength of Ni-based single-crystal superalloys under service condition is related to the thermo-mechanical properties of the disordered γ matrix. Here we use density functional theory and quasi-harmonic approximation to determine the temperature-dependent bulk moduli and generalized stacking fault energies (GSFEs) of Ni-Mo solid solutions. We show that the increasing temperatures between 1000 K and 1400 K cause evident reductions in the bulk moduli and planar fault energies of Ni-Mo alloys. Furthermore, their negative slopes versus temperature are gradually diminished with increasing Mo concentration except that of the unstable stacking fault energy. Adopting recent theoretical models for twinning based on GSFE, increasing temperature enhances the twinnability of low-Mo alloys but has limited influences in the case of high-Mo alloys. The composition-dependent thermal expansion, the thermal electronic excitation and the magnetic transition are shown to be the main factors rendering the complex variations in the elastic properties and twinning behavior of Ni-Mo solid solution with temperature.
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