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MM: Fachverband Metall- und Materialphysik

MM 30: Poster Session II

MM 30.6: Poster

Dienstag, 17. März 2020, 18:15–20:00, P4

Structural relaxation in nanocrystalline Pd90Au10 — •Christian Braun, Michael J. Deckarm, Nils Boussard, and Rainer Birringer — Experimental Physics, Saarland University, Germany

The synthesis of nanocrystalline (nc) materials -- either by the top-down or bottom-up approach -- results in non-equilibrated material states that strongly depend on the specific sample synthesis and preparation history. Energy in excess to the crystalline ground state is stored in the disordered core regions of the interfaces as well as strain energy associated with crystal lattice distortions and the presence of lattice defects. Hence, annealing of these materials at temperatures below grain growth induces structural relaxation/aging and as a consequence the core structure of interfaces and the material properties change with time. In nc materials, structural relaxation has to be considered as a heterogeneous process due to the complex structure of the grain boundary (GB) network which can be imagined as an assemblage of structural units characterized by a site-specific deviation from local equilibrium. To adapt these heterogeneous nature of the GBs, we employed a distributed reactivity model to analyze volume relaxation of nc Pd90Au10. This approach partitions the overall relaxation process into a set of independent and parallel reactions and was applied to a set of dilatometer data captured under different time-temperature protocols to probe the spectrum of potential barriers the material has to overcome on its way to equilibrium. Furthermore, we analyzed the corresponding change in mechanical properties and microstructure.