Hardness and fracture toughness enhancement in transition metal diboride multilayer films with structural variations

Publikationen: Beitrag in FachzeitschriftArtikelForschung(peer-reviewed)

Autoren

  • Marek Vidis
  • Tomas Fiantok
  • Marek Gocnik
  • Peter Jr Svec
  • Stefan Nagy
  • Martin Truchly
  • Vitalii Izai
  • Tomas Roch
  • Leonid Satrapinskyy
  • Viktor Sroba
  • Branislav Grancic
  • Peter Kus
  • Marian Mikula

Organisationseinheiten

Externe Organisationseinheiten

  • Comenius University, Bratislava
  • Comenius University
  • Slovak Academy of Sciences, Bratislava
  • Institue of Materials and Machine Mechanics, Slovak Akademy of Sciences

Abstract

The simultaneous enhancement of hardness (H) and fracture toughness (KIC) through the formation of super- lattice structures challenges the conventional belief that these quantities are mutually exclusive. Here, this approach has been applied to the transition metal diborides, whose inherent brittleness severely restricts their application potential. The mechanical properties of TiB2/TaB2 systems as a function of bi-layer period Λ are investigated, combining theoretical and experimental approaches. Density Functional Theory is used to inves- tigate the structural stability and mechanical properties of stoichiometric hexagonal TiB2/TaB2 superlattices for Λ = 3.9 – 11.9 nm. The calculations predict the highest H = 38 GPa and KIC (100) of 3.3 MPa.m1/2 at the value of Λ = 5.2 nm. Motivated by the theoretical results, multilayer films with Λ = 4–40 nm were prepared by direct current magnetron sputtering. Due to the sputtering effects, the deposited diboride films differ significantly from the view of stoichiometry and structure. A detailed structure investigation reveals TiB2/TaB2 in form of super- lattices exhibiting coherent interfaces for Λ = 4 nm. For higher Λ, parts of TaB2 layers transform from the crystalline to the disordered phase. These transformations are reflected in the mechanical properties as measured by nanoindentation and micromechanical bending tests. The evolution of hardness follows Hall-Petch behavior, reaching a maximum of 42 GPa at Λ = 6 nm. Enhancing fracture toughness involves more complex mechanisms resulting in two KIC maxima: 3.8 MPa.m1/2 at Λ = 6 nm and 3.7 MPa.m1/2 at Λ = 40 nm.

Details

OriginalspracheEnglisch
Aufsatznummer102070
Seitenumfang11
FachzeitschriftMaterialia
Jahrgang34.2024
AusgabenummerMay
DOIs
StatusVeröffentlicht - 21 März 2024