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Publications in Scientific Journals:

A Kirnbauer, A. Wagner, V. Moraes, D. Primetzhofer, M. Hans, J.M. Schneider, P. Polcik, P.H. Mayrhofer:
"Thermal stability and mechanical properties of sputtered (Hf,Ta,V,W,Zr)-diborides";
Acta Materialia, 200 (2020), 559 - 569.



English abstract:
Non-reactive magnetron sputtering of a diboride target composed of HfB2 , TaB2 , VB2 , W2 B5 , and ZrB2 with equimolar composition leads to the formation of crystalline single-phase solid solution diboride thin
films, (Hf,Ta,V,W,Zr)B2 , with a high-entropy metal-sublattice. Their growth morphology (dense and fine- fibrous), crystal structure (AlB2 -type), as well as mechanical properties (indentation modulus E of ~580
GPa and hardness H of ~45 GPa), and chemical compositions are basically independent of the substrate bias potential applied (varied between -40 and -100 V) during the deposition at 450° C.
Detailed X-ray diffraction (XRD) and atom probe tomography (APT) studies indicate that the (Hf,Ta,V,W,Zr)B2 thin films remain single-phase AlB2 -structured (with randomly distributed elements at the metal-sublattice) during vacuum-annealing at temperatures up to 1200° C. Only when increasing the annealing temperature to 1400° C, the formation of small orthorhombic structured (V,W)B-based regions can be detected, indicating the onset of decomposition of (Hf,Ta,V,W,Zr)B2 thin films into (Hf,Ta,Zr)B2 and (V,W)B, accompanied by the formation of confined B-rich boundary regions between these phases. After annealing at 1400° C the hardness is still very high with ~44 GPa, as the volume fraction of the newly formed (V,W)B-rich domains is small and the majority of the coating is still solid-solution (Hf,Ta,V,W,Zr)B2 with severe lattice distortions. Only at even higher Ta of 150 0 and 160 0 °C, H decreased to ~39 GPa.

Keywords:
High-entropy alloys (HEAs), Magnetron sputtering, Multi-element diborides, Thermal stability, High-entropy sublattice (HES)


"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
http://dx.doi.org/10.1016/j.actamat.2020.09.018


Created from the Publication Database of the Vienna University of Technology.