Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 57: Microstructure and Phase Transformations - transformation kinetics

MM 57.1: Vortrag

Donnerstag, 23. März 2017, 10:15–10:30, IFW B

Capturing the evolution of fractal abnormal grains in nanocrystalline Pd₉₀Au₁₀ — •Raphael Zeller¹, Harms Fey¹, Christian Braun², Philipp Romberger¹, Rainer Birringer², and Carl Krill¹ — ¹Institute of Micro and Nanomaterials, Ulm University, Germany — ²Experimental Physics, Saarland University, Germany

During abnormal grain growth, a bimodal size distribution is established by the rapid growth of a few grains to much larger sizes than their neighbors. Usually, such abnormal grains expand in all directions at roughly the same speed, but in nanocrystalline Pd₉₀Au₁₀, they appear to send out “tentacles” into the surrounding matrix, which ultimately results in highly irregular, fractal-like grain shapes. Exploiting the fast heating and cooling capabilities of a salt-bath furnace, we have investigated the evolution of fractal grain morphologies in nano-Pd₉₀Au₁₀, finding two surprises: higher temperatures sometimes lead to smaller grains, and longer annealing times do not necessarily promote further grain growth (but they can affect the fractal dimension of the grain shape). We discuss these results in the framework of standard growth models supplemented by ideas from nucleation theory.