Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 6: Computational Materials Modelling: Defects / Alloys
MM 6.10: Vortrag
Montag, 5. September 2022, 18:15–18:30, H44
Atomistic simulation of diffusion in γ′-strengthened Co-based superalloys — •Lin Qin1, Jutta Logal2,3, Dorota Kubacka4, and Ralf Dratz1 — 1ICAMS, Ruhr University Bochum, Bochum, Germany — 2Department of Chemistry, New York University, New York, United States — 3Department of Physics, Free University of Berlin, Berlin, Germany — 4Institute of Micro- and Nanostructure Research, FAU, Erlangen, Germany
The suppressed diffusion of Al in the strengthening γ′ precipitates in Co-based superalloys is suspected to be one plausible reason to cause the selective formation of alumina in the early stage of oxidation above 900∘C. In order to validate this assumption, the diffusion properties of Al, Co and W in a prototype structure of γ′ phase, i.e. L12-Co3(Al,W), are investigated with Density Functional Theory (DFT) and Kinetic Monte Carlo (KMC) simulations. DFT calculations reveal that the migration barrier of each element in Co sublattice is comparable with its respective barrier in pure Co. However, the crossover barriers of Al and W from their original positions to Co sublattice are much higher than the barriers for the reverse process. This large discrepancy in barriers constrains the site fraction of Al and W in Co sublattice, and therefore significantly suppresses the long-distance diffusion of Al and W in γ′ phase. KMC results show that Al diffusivity in γ′ phase is over two order of magnitudes lower than that in a solute γ phase (Co75Al12.5W12.5) at 900∘C, suggesting that the sluggish diffusion of Al in γ′ can be a possible reason to cause the selective formation of alumina in Co-based superalloys.