Dresden 2026 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 25: Interface Controlled Properties, Nanomaterials, and Microstructure Design I
MM 25.3: Vortrag
Mittwoch, 11. März 2026, 16:15–16:30, SCH/A215
Defect Phase Diagrams for Exploring Chemo-Structural Coupling in Ni Grain Boundaries — •Prince Mathews1, Ali Tehranchi1, Jörg Neugebauer2, and Tilmann Hickel1, 2 — 1Federal Institute for Materials Research and Testing (BAM), Berlin, Germany — 2Max Planck Institute for Sustainable Materials, Düsseldorf, Germany
The knowledge-driven framework of defect phase diagrams (DPDs) offers an effective and systematic approach to design materials with tailored properties. Unifying bulk and defect thermodynamics along with the consideration of structural and chemical complexities around defects, DPDs advance the fundamental understanding of defects and can also provide a pathway for guided microstructure design. In this work, we apply the framework of DPDs using ab-initio calculations to evaluate the stability of defect phases and investigate defect phase transformations in Ni grain boundaries. In competition with the nearest intermetallic phase, Nb containing defect phases are stable in Σ5 [001]/(310) whereas Nb containing defect phases are not stable in Σ3 [110]/(111) grain boundaries. Moreover, our findings indicate the preference of solutes to segregate at sites around defects with partial column occupations. Furthermore, with the application of a sub-lattice based model, we present the insights on grain boundary site column coverages as a function of temperature. In addition, we discuss a new approach for determining a characteristic defect width using the solute distribution probability across the defect which facilitates the integration of defects into the CALPHAD methodology.
Keywords: Defect Phase Diagrams; Grain Boundaries; Segregation; Ab-initio Thermodynamics; Nickel