Mesoscopic simulation of the influence of misfit dislocations on the morphology of the γ′-phase in Ni-Base superalloys
J. V. Görler.
Master Thesis, Ruhr-Universität Bochum, ICAMS, STKS, Bochum, Germany (2014)
Superalloys possess the ability to withstand high temperatures whilst maintaining their properties. The ability to endure high temperatures for prolonged periods of time is strongly linked to the unique microstructure of these materials. This microstructure is composed of thin γ-phase channels combined with dominant γ′-phase precipitates. To investigate the microstructural stability of the channels, dislocation induced strains at the interfaces are used to describe coherent and semi-coherent interfaces. A driving force which prevents precipitate coalescence is found. Moreover, it is shown that by transition from coherent to semi-coherent γ/γ′-interfaces precipitate coalescence is enabled. A phase-field simulation is used to investigate the microstructure evolution during long term aging of Ni-base superalloys. A similar model is used to simulate the effect of chromium on the microstructure of γ/γ′-forming cobalt-base superalloys.