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High temperature flow behavior of ultra-strong nanoporous Au assessed by spherical nanoindentation

Thursday (27.09.2018)
11:15 - 11:30 S1/01 - A03
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Nanoporous (NP) metal foams have attracted the attention of various research fields in the past years since their unique microstructures make them favorable for catalytic, sensory or microelectronic applications. Moreover, the refinement of the ligaments down to the nano-scale leads to an exceptional material strength. To guarantee a smooth implementation of nanoporous metals in modern devices their thermo-mechanical behavior must be properly understood. Within this study the mechanical flow properties of nanoporous Au were investigated at elevated temperatures up to 300 °C. In contrast to the conventional synthesis by dealloying of AuAg precursors the present foam was fabricated via severe plastic deformation of an AuFe composite and subsequent selective etching of iron. This route has two decisive advantages compared to NP Au obtained by dealloying. On the one hand, the ligaments themselves consist of nanocrystalline grains which further increases the material strength. On the other hand, remaining Fe impurities excessively stabilize the microstructure and impede coarsening of the ligaments within the examined temperature range. A recently developed spherical nanoindentation protocol was used to extract the mechanical flow behavior of NP Au and allows a comprehensive mechanical characterization of laboratory bench-scale materials. This efficient technique enables to link the microstructural features with the corresponding stress-strain behavior of the foam, showing a tremendous increase of yield strength due to ligament refinement which is maintained even at high temperatures. Furthermore, it will be discussed whether previous Berkovich nanoindentation studies are directly comparable to the novel spherical nanoindentation approach.

Dipl.-Ing. Alexander Leitner
Montanuniversität Leoben
Additional Authors:
  • Dr. Verena Maier-Kiener
    Montanuniversität Leoben
  • Dr. Daniel Kiener
    Montanuniversität Leoben