Strain-stabilized Al-containing high-entropy sublattice nitrides

Acta Materialia, vol. 224, pp. 117483

Abstract

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.

Authors 7

1. A. Kretschmer corresponding

   TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, TU Wien, Gumpendorferstraße 7, Vienna 1060, Austria

2. David Holec

   Montanuniversität Leoben

   Affiliation as printed

   Department of Materials Science, Montanuniversität Leoben, Franz-Josef-Strasse 18, Leoben A-8700, Austria

3. Kumar Yalamanchili

   Oerlikon (Liechtenstein)

   Affiliation as printed

   Oerlikon Balzers, Oerlikon Surface Solutions AG, Iramalli 18, Balzers 9496, Liechtenstein

4. Helmut Rudigier

   Oerlikon (Switzerland) · Oerlikon (Liechtenstein)

   Affiliation as printed

   OC Oerlikon Management AG, Pfäffikon 8808 SZ, Switzerland

   Oerlikon Balzers, Oerlikon Surface Solutions AG, Iramalli 18, Balzers 9496, Liechtenstein

5. Marcus Hans Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstraße 10, Aachen 52074, Germany

6. Jochen M. Schneider Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstraße 10, Aachen 52074, Germany

7. P.H. Mayrhofer

   TU Wien

   Affiliation as printed

   Institute of Materials Science and Technology, TU Wien, Gumpendorferstraße 7, Vienna 1060, Austria