SKM 2021 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 1: Topical Session Interface-Dominated Phenomena - Moving Interfaces

MM 1.2: Talk

Monday, September 27, 2021, 10:30–10:45, H8

Abnormal grain growth in nanocrystalline PdAu: The Case of the Fractal Fingerprint — Raphael A. Zeller¹, Christian Braun², Markus Fischer¹, Jörg Schmauch², Christian Kübel³, Rainer Birringer², and •Carl E. Krill III¹ — ¹Institute of Functional Nanosystems, Ulm University, Ulm, Germany — ²Department of Experimental Physics, Saarland University, Saarbrücken, Germany — ³Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany

In most polycrystalline materials, coarsening tends to be a civilized affair, with adjacent grains taking pains to exchange atoms so as to maintain a smooth boundary. The grains that grow in nanocrystalline PdAu, however, behave like uncouth neighbors crashing a fancy dinner party: once they get revved up, all hell breaks loose! Before you know it, a few nanometer-sized grains have grown four orders of magnitude in diameter, and the resulting interfaces are so convoluted that they resemble fractal objects. Our usual notion of curvature-driven grain boundary migration fails to explain the persistence of these interfacial fluctuations, but recent experiments find the onset of fractality to depend on the Au concentration as well as on a characteristic length scale. We consider this evidence to be a kind of “fractal fingerprint” that, ultimately, incriminates a specific mechanism as being responsible for the system’s abnormal grain growth.