Amin has successfully defended his MSc thesis on "Ab initio calculations of alloying impact on structural properties and stability of cementite" and has passed the final exam to get an MSc degree in Materials Science.
Congratulations!
The superlattice effect on mechanical properties was investigated in this paper. Namely, what is the impact of lattice mismatch for two elastically-matched systems. It has turned out that both hardness and marginally also fracture toughness exhibit the superlattice effect, although not as strong as for lattice-matched systems with different elastic moduli.
The work is a collaboration with the group of Paul Mayrhofer and Matthias Bartosik, TU Wien, Vienna, Austria.
J. Buchinger, A. Wagner, Z. Chen, Z.L. Zhang, D. Holec, P.H. Mayrhofer, M. Bartosik: "Fracture toughness trends of modulus-matched TiN/(Cr,Al)N thin film superlattices". Acta Mater., 202, 376–386 (2021). DOI: 10.1016/j.actamat.2020.10.068
In this work we focused on bcc-fcc martensitic transformations in Ti-Al-Mo ternary system, namely on the effect of Mo alloyed in TiAl on them. We could show that a tetragonal Bain path proceeds almost without any energy barrier between the ordered structure, hence suggesting spontaneous transformation into either γ-TiAl for low Mo content or to β-TiAl for Mo content above 8 at.%. Chemical disorder introduces barrier along the tetragonal path which to the stabilisation of the bcc β phase. Lastly, a potential connection via trigonal path has been ruled out due to too high transformation barriers.
The work is a collaboration with the group of Martin Friák and Mojmír Šob, Academy of Sciences, Brno, Czech Republic.
N. Abdoshahi, P. Spoerk-Erdely, M. Friák, S. Mayer, M. Šob, D. Holec: "Ab initio study of chemical disorder as an effective stabilizing mechanism of bcc-based TiAl+Mo". Phys. Rev. Materials, 4(10), 103604 (2020). DOI: 10.1103/PhysRevMaterials.4.103604
A small replacement for team-building activities which would have normally be a part of group's retreat. Starting at 5.30am from Leoben, we reached Präbichl started hiking around 6am. Summit photo has a timestamp 8.30am. Back in the office around 12noon. More photos in 2020 photo gallery.
By investigating structural and mechanical properties of MoN-TaN superlattices with different bilayer thickness, we develop coatings with high fracture toughness and hardness, stemming from the formation of a metastable tetragonally distorted phase of TaN up to layer thicknesses of 2.5 nm. Density functional theory calculations and experimental results further reveal a metal-vacancy stabilized cubic Ta0.75N phase with an increased Young’s modulus but significantly lower fracture toughness. The close interplay between our experimental and ab initio data demonstrates the impact of phase formation and stabilization on the mechanical properties of MoN-TaN superlattices.
The work is a collaboration with the group of Paul Mayrhofer, TU Wien, Vienna, Austria.
R. Hahn, N. Koutná, T. Wójcik, A. Davydok, S. Kolozsvári, C. Krywka, D. Holec, M. Bartosik, P.H. Mayrhofer: "Mechanistic study of superlattice-enabled high toughness and hardness in MoN/TaN coatings". Communications Materials, 1(1), 62 (2020). DOI: 10.1038/s43246-020-00064-4
The summer celebration with a group BBQ at David' garden becomes a tradition. Also this year :-)
In this work, the structural and mechanical properties of ternary Mo-Al-N alloys are investigated by combining thin film growth experiments and density functional theory (DFT) calculations. The experimental part was done by our French collaborators, groups of Gregory Abadias and Philippe Djemia.
F. Anğay, L. Löfler, F. Tetard, D. Eyidi, P. Djemia, D. Holec, G. Abadias: "Structure, stress, and mechanical properties of Mo-Al-N thin films deposited by dc reactive magnetron cosputtering: Role of point defects". J. Vac. Sci. Technol. A, 38(5), 053401 (2020). DOI: 10.1116/6.0000292
Summer holidays start off with a brand new publication. Together with colleagues from TU Wien and ESI, we show that KIC of TiN does not change (significantly) with temperature. The experimental findings are corroborated by modelling scaling from electronic structure, over molecular dynamics up to continuum level.
J. Buchinger, L. Löfler, J. Ast, A. Wagner, Z. Chen, J. Michler, Z.L. Zhang, P.H. Mayrhofer, D. Holec, M. Bartosik: "Fracture properties of thin film TiN at elevated temperatures". Mater. Des., 194, 108885 (2020). DOI: 10.1016/j.matdes.2020.108885
The CMS group has survived the social distancing caused by the corona outbreak without any damage. Not only we all have found out that we could do almost 100% of our work from home (or any other place with internet), but the group has been quite productive: both in getting new results as well as publishing them. Check out the list of new publications in 2020!
In order to keep tradition, we also this year we went for a half-day skiing at Präbichl. And Ganesh made his first few turns!
