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MM: Fachverband Metall- und Materialphysik

MM 27: Poster Session I

MM 27.26: Poster

Dienstag, 13. März 2018, 18:30–19:45, Poster E

Grain boundary morphologies in nanocrystalline Pd₉₀Au₁₀ go fractal: a simulation study of the growth kinetics — •Raphael Zeller¹, Christian Braun², Mingyan Wang¹, Rainer Birringer², and Carl E. Krill III¹ — ¹Institute of Micro and Nanomaterials, Ulm University, Germany — ²Experimental Physics, Saarland University, Germany

Although abnormal grain growth has been investigated for more than 70 years, our understanding of its underlying physics is still quite tenuous. For nanocrystalline materials, the situation is particularly unsatisfactory, as their dominant mode of coarsening appears to be abnormal. In samples of nanocrystalline Pd₉₀Au₁₀ produced by inert gas condensation, abnormal growth is marked by rapidly growing grains sending “tentacles” out into the surrounding matrix, quickly encircling nearby grains and then consuming them. The perimeters of the resulting grains—revealed in metallographic sections—resemble those of fractal objects, and the grain interiors contain a significant number of small-angle boundaries. Modifying a phase field-based model for grain growth, we assess the extent to which these observations are consistent with a growth process based on grain rotation. We find that fractality can be viewed as a consequence of regrouping contiguous matrix grains into larger, simply connected regions. The residual boundary roughness reflects the length scale of the initial grain size.