SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 23: Poster II

MM 23.32: Poster

Dienstag, 28. März 2023, 18:15–20:00, P2/OG1+2

Circularity: a microstructural clue to the origin of extreme abnormal grain growth in nanocrystalline Pd-Au — •Fabian Andorfer¹, Jules M. Dake¹, Johannes Wild², Torben Boll², Dorothée Vinga Szabó², Stefan Wagner², Astrid Pundt², and Carl E. Krill III¹ — ¹Institute of Functional Nanosystems, Ulm University — ²Karlsruhe Institute of Technology KIT

Heat treatment causes polycrystalline materials to manifest either normal or abnormal grain growth. During normal growth, the average grain size increases monotonically, but the grain size distribution remains unimodal. In contrast, when abnormal grain growth occurs, some grains acquire a significant growth advantage compared to the remaining matrix grains, resulting in a bimodal distribution of grain sizes. Inert-gas condensed nanocrystalline Pd-Au alloys undergo an extreme form of such abnormal grain growth: While the grain boundaries separating the abnormal and matrix grains in conventional samples tend to be rather smooth, in nanocrystalline Pd-Au the same boundaries take on rough and highly convoluted shapes - similar to a jagged coastline! In such cases, the measurement and calculation of grain circularity has proven to be a promising tool for classifying the nature of a given grain's abnormality. We have determined the circularity of abnormal grains emerging in nanocrystalline Pd-Au samples, and we have compared the results to values reported in the literature or obtained from simulations. From this information, we hope to gain a deeper understanding of the mechanism(s) responsible for the extreme growth mode observed in nanocrystalline Pd-Au.