Strain-stabilized Al-containing high-entropy sublattice nitrides

Andreas Kretschmer, David Holec, Kumar Yalamanchili, Helmut Rudigier, Marcus Hans, Jochen Michael Schneider, Paul Heinz Mayrhofer

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The impact of configurational entropy, enthalpy, and strain energy on the phase stability of high-entropy materials has not yet been investigated quantitatively. We used ab-initio calculations to predict the driving force for decomposition of 126 equimolar Al-containing high-entropy sublattice nitrides (HESN), which are all metastable with respect to all corresponding equimolar lower-entropy nitride phases. The entropy stabilization of ≈−0.06 eV/at. at 1073 K is overruled by the 0.10-0.27 eV/at. enthalpy-governed driving force for decomposition. Stabilization is however predicted for 22 compositions due to the −0.01 to - 0.28 eV/at. strain energy contribution caused by large differences in equilibrium volume between the HESN and their decomposition products. The predicted stabilities are consistent with diffraction and tomography data of annealed nitride coatings. Hence, it is evident that only strain enables the stabilization of the here studied Al-containing HESN, while the entropic contribution is overruled by endothermic mixing.

Original languageEnglish
Article number117483
Number of pages14
JournalActa materialia
Issue number1 February
Early online date2 Dec 2021
Publication statusPublished - 1 Feb 2022

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