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MM: Fachverband Metall- und Materialphysik
MM 30: Poster Session II
MM 30.4: Poster
Dienstag, 17. März 2020, 18:15–20:00, P4
Fractal abnormal grain growth in nanocrystalline Pd(Au): correlation between Au concentration, hardness and microstructure — •Markus Fischer1, Raphael Zeller1, Christian Braun2, Jonas Endres1, Rainer Birringer2, and Carl E. Krill III1 — 1Institute of Functional Nanosystems, Ulm University, Germany — 2Experimental Physics, Saarland University, Germany
With an average grain size below 100 nm, nanocrystalline materials often manifest enhanced mechanical properties, like higher strength or hardness, but the fine microstructure tends to go hand in hand with poor stability against grain growth. The latter generally starts at much lower temperatures than in coarser-grained specimens of the same material, and the coarsening process itself can proceed in an abnormal manner. In nanocrystalline Pd90Au10 alloys prepared by inert gas condensation (IGC), 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 ∼ 1.2; this value is significantly greater than the dimension of unity for grain perimeters of conventional samples [1]. However, when Au-free nanocrystalline Pd is prepared by IGC, grain growth leads to smaller grains at impingement and smoother boundaries. To shed light on the role played by Au atoms during the coarsening of nanocrystalline Pd(Au), we have searched for correlations between grain morphology, local hardness (as revealed by nanoindentation) and the Au concentration.
[1] C. Braun et al., Scientific Reports 8 (2018) 1592