Speaker
Description
The degrading effect hydrogen has on the mechanical properties of metals has been frequently observed in the past. Yet, the exact mechanics are not fully understood. These mechanisms do not only depend on environmental and mechanical conditions, like atmospheric composition or applied stresses, but also highly on the microstructure of the materials. Because hydrogen is not homogeneously distributed in a metal, but rather segregates to trapping sites like vacancies, dislocations, precipitates or grain boundaries, locally resolved approaches are mandatory if specific mechanisms are to be investigated.
For this approach, a relatively new technique to measure local hydrogen contents, Scanning Kelvin Probe Force Microscopy (SKPFM), is used in conjunction with different nano- and micromechanical methods. Microstructural features which appear interesting in the SKPFM measurements can then be separated and investigated using these nano- and micromechanical techniques to get a better understanding of the hydrogen-assisted mechanical degradation. One of the biggest challenges for these experiments is to reliably introduce hydrogen during the measurements, wherefore we introduce in situ setups for both the SKPFM measurements and the nano-/micromechanical tests in which the specimens are either charged electrochemically or with a plasma of a hydrogen gas mixture.
Grain boundaries are one of the most prominent trapping sites, but their interaction with hydrogen differentiates strongly between different types of grain boundaries. Macromechanical experiments have shown in the past that premature failure of grain boundaries is the main mechanism in many alloys, as they switch from ductile failure to brittle intergranular cracking with increasing hydrogen contents. Therefore, grain boundaries are the main focus of the presented work.
| Speaker Country | Germany |
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