Berlin 2018 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 32: Microstructure and Phase Transformations
MM 32.4: Talk
Wednesday, March 14, 2018, 11:00–11:15, TC 010
Abnormal coarsening of nanoscale microstructures goes fractal — •Christian Braun1, Raphael Zeller2, Carl Krill2, and Rainer Birringer1 — 1Experimental Physics, Saarland University, Germany — 2Institute of Micro and Nanomaterials, Ulm University, Germany
Despite the supposed rarity implicit in its name, abnormal grain growth (AGG) appears to be a rather common mode of coarsening in nanocrystalline materials, regardless of composition or synthesis route. In inert-gas-condensed nanocrystalline Pd90Au10, thermally induced coarsening fulfills the criteria for AGG, but with an unusual twist: here, the subpopulation of abnormally growing grains sends offshoots in many directions into the surrounding matrix. The resulting irregular growth fronts manifest a fractal-like morphology characterized by a box-counting fractal dimension of 1.2 instead of the smooth interfaces observed in conventional samples. To gain insight into the nonstandard mechanisms and driving forces initiating and accordingly acting during this mode of coarsening in nanocrystalline PdAu-alloys, it is required to answer amongst others the following questions: Are there further differences in the coarsened morphology compared to conventional samples prepared by melting and solidification? What about correlations between fractality and local characteristics in microstructure? Can the fractal dimension be influenced by a variation of gold concentration, heating rate and dwell time? In this talk we will present our recent results to narrow down potential mechanisms responsible for fractal grain boundary migration in nanocrystalline metals.