Effect of local chemistry on microstructural stability and local deformation mechanisms in relation to hydrogen embrittlement of Fe base fcc alloys

点击翻译按钮获取中文摘要

Hydrogen embrittlement of technical Fe base alloys with face centered cubic crystal structure is a topic that has been intensively investigated for decades. The reason for that is the high technical relevance of this topic. It gains even more importance due to the recent discussion on renewable energy sources and the use of hydrogen for energy storage. Concerning embrittlement mechanisms of metals, mainly three theories are discussed in literature, namely the hydrogen induced decohesion, the formation of metal hydrides, and the HELP mechanism (hydrogen enhanced localized plasticity). For certain, usually standardized, alloys, the mechanisms of hydrogen embrittlement are known. However, for austenitic steels there is still a lack of information to relate the macroscopic properties in the presence of hydrogen with microstructural properties, the latter being a result of production and processing of these high-alloyed materials. Published works often makes use of well-known and standardized materials without considering the procedural and thermomechanical history. The objective of the research project is to make a contribution to fill this gap of knowledge. To do so, pre-defined model systems of iron based alloys shall be investigated with respect to solidification and distribution of alloying elements being a result of segregation. Simulations on the basis of the CALPHAD and the phase field method will be applied along with WDS- and EDS-measurements. Investigations of the local deformation and failure mechanisms with and without the presence of external hydrogen will be performed ex-situ by space-resolved diffraction methods (EBSD). The overall aim of the research project is the prediction of local chemical compositions and to derive local materials properties (e.g. phase stability, stacking fault energy) from that. Finally, this information shall be correlated with the local influence of hydrogen that controls the macroscopic properties of the material.