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Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Dalian University of Technology, China.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. (EGENSKAPER)ORCID iD: 0000-0001-9317-6205
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.ORCID iD: 0000-0001-5676-418X
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
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2016 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 28, no 29, article id 295501Article in journal (Refereed) Published
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Text
Abstract [en]

To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-yRexOsy (0 <= x, y <= 6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C-11, the other elastic parameters including C-12, C-44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-yOsy than in W1-xRex. A strong correlation between C' and the fcc-bcc structural energy difference for W1-x-yRexOsy is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016. Vol. 28, no 29, article id 295501
Keywords [en]
disordered W-Re-Os alloys, elastic properties, ductility, solid-solution hardening
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-189354DOI: 10.1088/0953-8984/28/29/295501ISI: 000377504100007Scopus ID: 2-s2.0-84975057100OAI: oai:DiVA.org:kth-189354DiVA, id: diva2:948151
Note

QC 20160708

Available from: 2016-07-08 Created: 2016-07-04 Last updated: 2018-09-12Bibliographically approved
In thesis
1. First-principles study of materials for advanced energy technology
Open this publication in new window or tab >>First-principles study of materials for advanced energy technology
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis addresses promising material solutions for fusion reactors from a theoretical point of view. We focus on two specific systems: W-based alloys used as plasma-facing materials and reduced activation ferritic/martensitic (RAFM) steels used as structural materials of breeding-blanket. We aim to systematically investigate the alloying effects on the micro-mechanical properties of these body-centered cubic (bcc) solid solutions. The all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA) are the main tools for our theoretical studies. The knowledge of the elastic parameters and their solute-induced changes is important for alloy design and for a multi-scale modeling approach to the mechanical properties. We also explore the planar faults in the present alloys by studying the surface and unstable stacking fault energies. In part one, the effect of neutron transmutation elements on the elastic properties of the W-based alloys are calculated. Both Re and Os solute atoms shrink the lattice constant, which lead to increasing bulk modulus as the amount of Re or Os increases. The polycrystalline shear and Young’s moduli of W1−x−yRexOsy (0 ≤ x, y ≤0.06) enhance with the addition of Re but decrease with increasing Os. From the variations of the Cauchy pressure, Poisson ratio, Pugh ratio B/G, and the ratio of cleavage energy to shear modulus for the dominant slip system, we conclude that the intrinsic ductility of the alloy increases with increasing Re and Os content. The classical Labusch-Nabarro model for solid-solution hardening predicts that strengthening effects in W1−yOsy is larger than those in W1−xRex. We use the energy difference between the face centered cubic (fcc) and bcc structures to estimate the alloying effect on the ideal tensile strength in the [001] direction. Within a simple empirical equation, we find that the melting temperature of W-Re-Os alloy decrease with Re and Os addition. In part two, we investigate the micro-mechanical properties of the main alloy phases of three reduced activation ferritic/martensitic (RAFM) steels: CLAM/CLF-1, F82H, and EUROFER97. Being the main building blocks of the RAFM steels, first the lattice parameters, elastic properties, surface energy and unstable stacking fault energy of ferromagnetic α-Fe and Fe91Cr9 are calculated for reference. For quantitative understanding, we present a detailed analysis of the calculated individual alloying effects of V, Cr, Mn, and W on the elastic properties of Fe91Cr9. A linear superposition of these individual rates on the elastic properties of RAFM steels is shown to reproduce well the values from ab initio calculations. The composition dependence of the elastic constants is decomposed into electronic and volumetric contributions and analyzed. Finally, the intrinsic ductility is evaluated through Rice’s phenomenological theory by using the ratio of surface and unstable stacking fault energies. The results are consistent with those obtained by the common empirical criteria.

Place, publisher, year, edition, pages
Kungliga Tekniska högskolan, 2018. p. 39
Series
TRITA-ITM-AVL ; 2018:48
National Category
Other Mechanical Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-234895 (URN)978-91-7729-907-3 (ISBN)
Presentation
2018-10-04, N111, Brinellvägen 23, KTH, Stockholm., 10:00 (English)
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Supervisors
Note

QC 20180912

Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2018-09-18Bibliographically approved

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