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MM: Fachverband Metall- und Materialphysik

MM 29: Microstructure and Phase Transformations

MM 29.7: Vortrag

Mittwoch, 3. April 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.