Effect of the internal oxidation on the mechanical properties

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Internal oxidation is known for its detrimental effects on materials as well as for the possibility to produce microstructures like in ODS alloys. In both cases oxygen diffuses from the surface into the material in order to oxidize the less noble components of the alloy. The diffusion paths that are discussed at the moment are the diffusion through the metallic matrix and the diffusion along the incoherent phase boundaries metal/oxide. Oxygen diffusion through the oxide phase is often regarded as negligible as the diffusion in oxides is often much lower than in the metallic matrix. But the diffusion through the oxide phase can also be the rate controlling step for the internal oxidation if oxygen conducting oxides are formed. An example therefore is the system Ni-Zr-Y. There YSZ is formed during internal oxidation which is well known for its oxygen conducting properties. Oxidation rates in this system can be increased by three orders of magnitude compared to classical theory. Self-organized, interpenetrating networks of oxide and metal are formed. The aim of this project is to describe the potential and limitations of the internal oxidation that is based on the oxygen diffusion through the oxide phase. This includes the identification of further alloy systems as well as the investigation of material properties in those microstructures.