Novel methods for micromechanical examination of hydrogen and grain boundary effects on dislocations

Abstract

Most of what is known about the local interaction of dislocations with grain boundaries and hydrogen is based on transmission electron microscopy studies, which suffer from the distinct disadvantage that only extremely thin samples can be used. Recently, micropillar compression testing has become a popular means by which investigation of the size effect is conducted. This method, in combination with orientation imaging techniques, is used here to study the interaction of dislocations with a pre-selected grain boundary during the deformation of a bicrystalline specimen. Furthermore, by utilizing a custom built electrochemical cell, the micropillar compression testing can be extended to study in situ examination of micropillars charged with hydrogen. The effects of hydrogen and grain boundary on the deformation process in this small, but still bulk-like volume are presented, and our initial results reveal the value of this new technique for investigations of hydrogen embrittlement and grain boundary strengthening.

Keywords:

• nanoindentation
• dislocations
• mechanical properties
• nickel
• grain boundaries
• FIB
• EBSD
• electrochemical hydrogen embrittlement
• micropillar compression
• bicrystal