Print Email Facebook Twitter Phonon broadening in high entropy alloys Title Phonon broadening in high entropy alloys Author Körmann, F.H.W. (TU Delft (OLD) MSE-7) Ikeda, Yuji (Kyoto University) Grabowski, Blazej (Max-Planck-Institut für Eisenforschung) Sluiter, M.H.F. (TU Delft (OLD) MSE-7) Date 2017 Abstract Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation high-temperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In contrast to perfect crystals and ordered alloys, the inherently present mass and force constant fluctuations in multi-component random alloys (high entropy alloys) can induce significant phonon scattering and broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of 12 body-centered cubic random alloys, from binaries up to 5-component high entropy alloys, addressing the key question of how chemical complexity impacts phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability considerations. The set of studied alloys includes MoTa, MoTaNb, MoTaNbW, MoTaNbWV, VW, VWNb, VWTa, VWNbTa, VTaNbTi, VWNbTaTi, HfZrNb, HfMoTaTiZr. Subject Computational methodsMetals and alloysOA-Fund TU Delft To reference this document use: http://resolver.tudelft.nl/uuid:0ae96102-60c3-4dda-8e6f-deaa23346fb2 DOI https://doi.org/10.1038/s41524-017-0037-8 ISSN 2057-3960 Source npj Computational Materials, 3 Part of collection Institutional Repository Document type journal article Rights © 2017 F.H.W. Körmann, Yuji Ikeda, Blazej Grabowski, M.H.F. Sluiter Files PDF s41524_017_0037_8.pdf 3.68 MB Close viewer /islandora/object/uuid:0ae96102-60c3-4dda-8e6f-deaa23346fb2/datastream/OBJ/view