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M.Sc. David Piorunek
Lehrstuhl Werkstoffwissenschaft
Institut für Werkstoffe
Fakultät für Maschinenbau
Ruhr-Universität Bochum
Universitätsstr. 150
44780 Bochum

Gebäude ICFO, Ebene 04, Raum 343
Activities: Research Assistant
Chemical complexity and shape memory alloys. David Piorunek works on the influence of increasing chemical complexity on the properties of Ni-Ti-derived high-entropy (HE) shape memory alloys (SMA). The focus of the current project, which is part of the DFG Priority Program 2006 on chemically complex and high-entropy alloys, is the fundamental understanding of the interaction between microstructure and martensitic phase transformations as a function of increased alloy complexity. Here, Ni-equivalent alloying elements (AE) such as Cu, Co or Pd as well as Ti-equivalent AEs such as Zr or Hf are added to the Ni-Ti alloy in high concentrations in order to increase the entropy of mixture and thus establishing optimum values of the Gibbs free energy. Alloys are produced follow-ing ingot metallurgy processing routes derived from processes which were previously established for Ni-Ti shape memory alloys. Chemical complexity, however, leads to complex cast microstructures and casting defects which are undesireable. The project aims at suppressing these microstructural features by appropriate processing strategies. Scanning and transmission electron microscopy are combined with chemical and thermal analysis to explore the relations between microstructure, alloy composition and functional properties.

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