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Thermodynamic reassessment of the Ni-Ru system and assessment of the Al-Ni-Ru system at 1273-1523 K using ab initio calculations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.ORCID iD: 0000-0002-4521-6089
2008 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 56, no 15, 4062-4069 p.Article in journal (Refereed) Published
Abstract [en]

The Ni-Ru and Al-Ni-Ru systems are assessed with a combined CALPHAD and ab initio approach. Particular attention is paid to the possible existence of a miscibility gap in the B2 phase. Both face-centered cubic and body-centered cubic ordering are analyzed within the compound energy formalism. Ab initio calculations for the B2 phase show a similar trend as calorimetric measurements but the magnitude is much smaller. It is found that the calorimetric measurements cannot be reconciled with any reasonable phase diagram, whereas the ab initio results can. From the parameters obtained, isothermal sections in reasonable agreement with experimental phase diagrams are calculated. We have concluded that there is no miscibility gap in the B2 phase at 1273 K and higher temperatures.

Place, publisher, year, edition, pages
2008. Vol. 56, no 15, 4062-4069 p.
Keyword [en]
thermodynamics, CALPHAD, intermetallics, ab initio electron theory, enthalpy of formation, total-energy calculations, augmented-wave method, basis-set, phase, approximation, metals, exchange, alloys
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-17840DOI: 10.1016/j.actamat.2008.04.028ISI: 000259409300034Scopus ID: 2-s2.0-48449083486OAI: oai:DiVA.org:kth-17840DiVA: diva2:335885
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. On high temperature oxidation resistance: Towards the materials genome of high temperature alloys
Open this publication in new window or tab >>On high temperature oxidation resistance: Towards the materials genome of high temperature alloys
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The efficiency of a heat engine increases with increasing service temperature. This leads to a demand for material that can withstand aggressive environments and sometimes also high load at higher and higher temperature. That is the rationale for the work of this thesis. It is divided into two parts, both addressing model alloy systems for components used in oxidizing high temperature environments. In the first part the phase equilibria and phase diagrams of Ni-Ru and Al-Ni-Ru are investigated from a thermodynamic point of view using the well known Calphad method. In particular, the debated existance of a miscibility gap between the aluminides NiAl and RuAl is considered. This led to a combined ab initio/Calphad approach and it is suggested that there is a miscibility gapat low temperature. In the second part, first of its kind diffusion simulations in oxides are performed in the technologically important Fe-O and Cr-O systems. In the simulations, the moving phase boundary problem is solved with use of temperature and composition dependent diffusion coefficients, that are evaluated for complex oxide phases modeled with up to four sublattices. This type of simulations attracts a lot of interest and it looks very promising for future extension to higher order systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vii, 32 p.
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-154227 (URN)978-91-7595-313-7 (ISBN)
Public defence
2014-11-14, B2, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141222

Available from: 2014-10-22 Created: 2014-10-15 Last updated: 2014-10-23Bibliographically approved

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