Papers

ICMCTF 2022 Session F2-1-TuM: High Entropy and Other Multi-principal-element Materials I

Tuesday, May 24, 2022 8:00 AM in Room Town & Country C

Tuesday Morning

Start	Invited?	Item
8:20 AM		F2-1-TuM-2 Elaboration and Characterization of High Entropy Nitride Al-Ti-Zr-Ta-Hf (-N) Deposited by Reactive Magnetron Sputtering for High Temperature Applications Djallel Eddine TOUAIBIA, Mohamed ELGARAH, Sofiane ACHACHE (LASMIS); Alexandre MICHAU, Frederic Schuster (Commissariat à l'Energie Atomique et aux énergies alternatives (CEA) Saclay); Frederic SANCHETTE (University of Technology Troyes (UTT)) AlTiTaZrHf(-N) high entropy nitrides films were deposited in various argon-nitrogen gas mixtures on glass and silicon substrates. X-ray diffraction analyses reveal a transition from amorphous to an FCC single phase by increasing the nitrogen content. Films morphology is not influenced by nitrogen content, all films have a compact morphology. Energy dispersive spectroscopy analysis shows an increasing of the film nitrogen content when the flow rates ratio RN2=N2/Ar+N2 varies between 0 and 15% and stabilizes above. Evolution of hardness and Young’s modulus are discussed and the maximum values are obtained for a flow rates ratio RN2 of 10% at 27.67 GPa and 205.56 GPa respectively. Chemical bonds and tribological performances will be discussed and high temperatures stability is investigated.
8:40 AM		F2-1-TuM-3 Strain-Stabilized Al-Containing High-Entropy Sublattice Nitrides Andreas Kretschmer, Balint Hajas (TU Wien, Institute of Materials Science and Technology); David Holec (Montanuniversitat Leoben, Austria); Kumar Yalamanchili, Helmut Rudigier (Oerlikon Balzers, Oerlikon Surface Solutions AG); Marcus Hans, Jochen Michael Schneider (RWTH Aachen University); Paul Heinz Mayrhofer (TU Wien, Institute of Materials Science and Technology) 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 were validated with diffraction and tomography data of 9 annealed nitride systems. 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.
9:00 AM		F2-1-TuM-4 Structural and Mechanical Properties Investigation of a New TiTaZrHfW(-N) Refractory High Entropy Films Deposited by Reactive Magnetron Sputtering Abdelhakim Bouissil, Sofiane Achache, Frederic Sanchette, Mohamed El Garah (LASMIS, Antenne de Nogent, Université de Technologie de Troyes) In the last decade, refractory high entropy thin films have attracted more attention due their superior proprieties at high temperatures [1]. Besides the thermal stability, these new materials present a good resistant to oxidation and can also keep good mechanical properties, high hardness and elastic modulus etc, at temperature up to 1600 °C, which is interesting compare to conventional alloys [2][3]. TiTaZrHfW(-N) films are synthesized by reactive magnetron sputtering in various argon plus nitrogen atmospheres. The microstructure, mechanical and thermal properties are investigated. Optical emission spectroscopy is performed to analyze the target nitriding conditions and to optimize the deposition parameters. The nitrogen flow rate ratio R_N₂=Φ_N₂/(Φ_N₂+Φ_Ar) is varied from 0 to 30%. XRD analyses show a transition from an amorphous structure to FCC single phased films once the nitrogen is added (5%). By increasing the nitrogen flow rate, preferential orientation from {111} to {200} is observed. The morphology of the films changes from compact to columnar when the nitrogen ratio exceeds 5%. The hardness and Young’s modulus are also studied and the maximum values, 29 GPa and 257 GPa respectively, are obtained at R_N₂= 9%. All nitrides show a good thermal stability under vacuum at 800 °C for three hours compared to metallic film, for which phase transition occurs. [1] O. N. Senkov, D. B. Miracle, K. J. Chaput, et J.-P. Couzinie, « Development and exploration of refractory high entropy alloys—A review », J Mater Res, vol. 33, n^o 19, p. 37, 2018. [2] P.-K. Huang et J.-W. Yeh, « Inhibition of grain coarsening up to 1000°C in (AlCrNbSiTiV)N superhard coatings », Scr. Mater., vol. 62, n^o 2, p. 105–108, janv. 2010, doi: 10.1016/j.scriptamat.2009.09.015. [3] O. N. Senkov, G. B. Wilks, J. M. Scott, et D. B. Miracle, « Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys », Intermetallics, vol. 19, n^o 5, p. 698–706, mai 2011, doi: 10.1016/j.intermet.2011.01.004.