Creep and microstructure in directionally solidified NiAl(Cr)-Mo alloys

0450284 - ÚFM 2016 RIV CZ eng A - Abstract
Dudová, Marie - Bei, H. - Somsen, C. - George, E.P. - Dlouhý, Antonín
Creep and microstructure in directionally solidified NiAl(Cr)-Mo alloys.
Book of Abstracts. 17th International Conference on the Strength of Materials (ICSMA-17). Brno: Ústav fyziky materiálů AV ČR, v. v. i., 2015 - (Dlouhý, A.; Kunz, L.). s. 85-85. ISBN 978-80-87434-07-9.
[ICSMA-17 International Conference on the Strength of Materials /17./. 09.08.2015-14.08.2015, Brno]
R&D Projects: GA ČR(CZ) GA202/09/2073
Institutional support: RVO:68081723
Keywords : High-temperature creep * In-situ composite * Directional solidification * Eutectics
Subject RIV: JI - Composite Materials

We present NiAl(Cr)-Mo directionally solidified alloys exhibiting high temperature strength due to regularly distributed fine eutectic phases Mo or Cr. These eutectics exhibited minimum creep rates that were up to seven orders of magnitude lower than the corresponding minimum creep rates of the NiAl matrix alloy and pure Mo or Cr single phases. We present detailed analysis of dislocation structures observed in the as-grown crystals as well as in the eutectics after creep. Clear evidence is provided showing that Mo and Cr phases contain essentially no dislocations before creep and the appropriate dislocation densities after creep. These results suggest that the immense hightemperature strength of the NiAl(Cr)-Mo eutectics can be attributed to the load bearing capacity of dislocation-free nano-reinforcements. These phases support the load transferred from the plastically deforming NiAl matrix up to the point when they yield. A statistically relevant yielding of the reinforcement is reflected in the gradual increase of creep rate with accumulated creep strain.
Permanent Link: http://hdl.handle.net/11104/0251675