In-situ electro chemical micro cantilever bending test of bicrystal beamsWednesday (28.09.2016) 17:30 - 17:45 Part of:
Hydrogen Induced degradation of structural materials has been an important research topic for the last decades. Since hydrogen has a strong tendency to segregate in structure defects, grain boundary (GB) importance becomes even more dominated in the hydrogen embrittlement studies. GBs are considered as one of the potential sites for initiation of this catastrophic phenomenon in the polycrystalline materials. Considering that dislocations are the carrier of plastic deformation, there is a demand for a method capable to probe GB interaction with dislocations in the presence of hydrogen. In this study, we introduce an in-situ electro chemical micro cantilever bending (ECCB) test of bicrystal beams with a selected type of GB. This setup is the integration of an especial three electrodes electrochemical cell in the nano-indenter. Charging the Fe- 3% Si sample cathodically during the in situ ECCB testing of micro sized bicrystal beams, assured uniform concentration of hydrogen in the GB during the bending test. The results was compared with the bicrystal cantilevers bended in the air. Secondary electron imaging and electron backscatter diffraction were used to analyze the deformation substructures after the test. The load-displacement curves reveal continuous decrease in the flow stress for the cantilevers was bended with the presence of hydrogen. The flow stress was constant for the beams was bended in the air. The secondary electron images show a crack propagation in the presence of hydrogen. This method overcomes the problems that arise from out gassing of hydrogen during ex-situ testing. Furthermore, examination of hydrogen interaction with a specific type of GB is in the same microstructural length scale.
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