To view the poster program please click here

Back to overview

Lecture

First results on thermal stability and mechanical behaviour of CrFeCoNi equiatomic compositionally complex alloy thin films on silicon and sapphire

Thursday (27.09.2018)
10:30 - 10:45 S1/01 - A5
Part of:


This presentation summarizes the first results obtained in the AHEAD (‘Analysis of the stability of High Entropy Alloys by Dewetting of thin films’) joint project (ANR-DFG) on thin films of compositionally complex alloys (CCA)/ High entropy alloys (HEA). The advantages of thin film processing include formation of alloys with a wide composition range by rapid combinatorial synthesis [1,2].

In the present study, quaternary equiatomic CCA thin films of CrFeCoNi were deposited on SiOx or SiN covered Si and (0001) sapphire substrates by magnetron sputtering. As-deposited and annealed films were characterized by XRD, SEM-EBSD and TEM studies.

As-deposited films were nanocrystalline on all substrates. Upon annealing, most of the grains in the film on c-sapphire attained epitaxial orientation relationships (ORs) where close-packed planes and directions of the film and substrate are parallel: either {111}fcc || (0001)sapphire and <110>fcc || <10-10>sapphire (OR I) or {111}fcc || (0001)sapphire and <110>fcc || <11-20>sapphire (OR II). The grains in OR I are more frequent on annealing at temperatures below 1000°C while at higher annealing temperatures, OR II is preferred. The ORs show interesting similarities with those found for Cu and Al films on (0001) sapphire [3,4]. In addition, we observe that when a thick Cr2O3 layer grows on the top of the CCA and oxide inclusions of CrO3 form in the interior, they adopt specific ORs with the quaternary fcc phase.

In films on Si with a diffusion barrier of SiOx or SiN, the fcc phase was found to be stable under thermal cycling to 500°C. However, oxidation starts in medium vacuum conditions at ~400°C forming Cr2O3. The films are studied further for phase and microstructure stability under thermal fatigue and mechanical deformation.


Acknowledgements:

GD, AL, CS, DC and NB acknowledge funding of the project ‘Analysis of the stability of High Entropy Alloys by Dewetting of Thin Films (AHEAD)’ by DFG and ANR.


References:

1. YJ Li, A Savan, A Kostka, HS Stein and A Ludwig, Mater. Horizons, 5 (2018) 86-92

2. A Marshal, KG Pradeep, D Music, S Zaefferer, PS De and JM Schneider, J All Compd, 691 (2017) 683-689

3. G Dehm, H Edongue, T Wagner, SH Oh and E Arzt, Z. Metallkd. 96 (2005) 249 – 254

4. SW Hieke, B Breitbach, G Dehm and C Scheu, Acta Mater., 133 (2017) 356 - 366

 

Speaker:
Maya Katapadi Kini
Max-Planck-Institut für Eisenforschung GmbH
Additional Authors:
  • Wenjun Lu
    Max-Planck-Institut für Eisenforschung GmbH
  • Alan Savan
    Ruhr-Universität Bochum
  • Bladine Courtois
    Aix-Marseille University - CNRS CINAM
  • Younes Addab
    MINES ParisTech, PSL - Research University
  • Benjamin Breitbach
    Max-Planck-Institut für Eisenforschung GmbH
  • Dominique Chatain
    Aix-Marseille University - CNRS CINAM
  • Alfred Ludwig
    Ruhr-Universität Bochum
  • Nathalie Bozzolo
    MINES ParisTech, PSL - Research University
  • Christian Liebscher
    Max-Planck-Institut für Eisenforschung GmbH
  • Christina Scheu
    Max-Planck-Institut für Eisenforschung GmbH
  • Christoph Kirchlechner
    Max-Planck-Institut für Eisenforschung GmbH
  • Gerhard Dehm
    Max-Planck-Institut für Eisenforschung GmbH