Regensburg 2019 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 29: Microstructure and Phase Transformations
MM 29.7: Talk
Wednesday, April 3, 2019, 16:45–17:00, H46
Fractal abnormal grain growth in nanocrystalline Pd90Au10: an experimental study of factors influencing interface fractality — •Christian Braun1, Raphael Zeller2, Hanadi Menzel1, Nils Boussard1, Jörg Schmauch1, Carl E. Krill III2, and Rainer Birringer1 — 1Experimental Physics, Saarland University, Germany — 2Institute of Functional Nanosystems, Ulm University, Germany
With grain sizes below 100 nm, nanocrystalline materials are characterized on the one hand by beneficial properties like high strength, while, on the other hand, being thermally unstable. Grain growth generally starts at temperatures that are significantly lower than usual, and microstructural coarsening often proceeds in an abnormal manner. In nanocrystalline Pd90Au10 alloys prepared by inert gas condensation, such abnormal growth leads to an impinged state of grains exhibiting highly irregular shapes, the perimeters of which are characterized by a box-counting fractal dimension of about 1.2.
Insight into the growth mechanism(s) underlying these observations could potentially be gained from a detailed analysis of interface fractality, provided the following questions can be answered: Does self-similarity in grain morphology start from the elementary building blocks of the initial microstructure (i.e., individual nanograins) or at a larger length scale? Does the fractal dimension of an abnormal grain boundary differ between its mobile and impinged states? For both questions, it is important to assess the influence of the Au concentration on abnormal grain nucleation and boundary fractality.