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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Postersession KFM

KFM 14.30: Poster

Mittwoch, 3. April 2019, 16:00–18:30, Poster C

On the effect of high current densities on thin iron-carbon alloy films — •Thomas Brede, Christine Borchers, Reiner Kirchheim, and Cynthia Volkert — Institut für Materialphysik, Georg-August-Universität, Göttingen, Deutschland

The recently discovered flash sintering method for preparing high quality oxide materials can be applied to the preparation of high performance nanocrystalline metals as well. Just as for the oxide materials, it is possible to use electric fields and currents to enhance densification of metal powders while limiting grain growth, however, the exact mechanism is still under discussion. The goal of our study is to understand how electric currents effect impurity redistribution and grain growth in fine grained metals.

Thin nanocrystalline iron films with high carbon concentrations are prepared as a model system and to compare with the behavior of nanocrystalline bulk samples. The thin film samples are heated and exposed to high current densities comparable to those experienced during the sintering process of bulk materials and the evolution of the microstructure, morphology and carbon concentration are investigated using electron microscopy. Extensive effects of the electrical current on C redistribution and grain growth are observed, including strong coupling between grain growth and C content and the formation of grains that are elongated along the direction of the current. The various microstructural observations will be summarized and possible explanations will be discussed.