Seminars and Events

Characterization and modeling of the propagation of creep dislocations from the interdendritic boundaries in single crystal Ni base superalloys

Date/Time: 15.09.2014. 4:30 p.m.
Place: Ruhr-Universität Bochum, Bochum, Germany

Masood Hafez Haghighat, Department of Microstructure Physics and Metal Forming, Düsseldorf

In Ni base superalloys the initial dislocation density is always found to be very low, as observed for example using transmission electron microscopy. During the creep process the essentially dislocation-free regions are gradually percolated by multiplication of dislocations from sources, the origin of which have not been well understood. Interdendritic boundaries are known to exist in the as-cast structure of single crystal Ni base superalloys. In this study electron channeling contrast imaging (ECCI) is used to characterize the geometrically necessary dislocations (GND) at the interdendritic boundaries. Discrete islocation dynamics (DDD) simulation is used to model the propagation of the dislocations from the interdendritic boundaries through the γ-γ' microstructure of Ni base superalloys. The modeling approach allows the necessary contributions of dislocation climb process to the dislocation flow. Insights into the role played by the interdendritic boundaries are provided.

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