In situ electrochemical nanoindentation: A technique for local examination of hydrogen embrittlement

Nanoindentation combined with AFM (NI-AFM) has been used to study the effect of electrochemically in situ charged hydrogen on the deformation of small volumes of nickel and copper single crystals. Hydrogen reduces the unstable elastic plastic transition load (pop-in) in nickel, but does not have any effect on copper. It has been shown that the activation energy for the onset of plasticity (dislocation nucleation) is reduced by dissolved hydrogen. This is because hydrogen reduces shear modulus and stacking fault energy in nickel, whereby the former results in hydrogen-enhanced decohesion (HEDE) and the latter in the hydrogen-enhanced plasticity (HELP) mechanism.