Hydrogen effect on dislocation nucleation in a vanadium (100) single crystal as observed during nanoindentation

Correlation between the hydrogen chemical potential and pop-in load during in situ electrochemical nanoindentation

“…Then plasticity starts under this condition by HDN within this small sheared volume beneath the tip, and manifests itself in the form of a sudden jump in load-displacement curves, which is usually called pop-in or the yield point phenomenon [28][29][30][31]. There have been attempts to study the effect of hydrogen on dislocation nucleation by means of nanoindentation [32][33][34]. However, in all these attempts, the samples are charged ex situ and then tested with nanoindentation.…”

Chemomechanical effects on the separation of interfaces occurring during fracture with emphasis on the hydrogen-iron and hydrogen-nickel system

“…generation or motion, external or internal hydrogen will increase the rate of both processes. It has been shown experimentally and theoretically [3,[38][39][40][41] that hydrogen will reduce the formation energy of dislocations like it decreases the surface formation energy and thus it increases the rate of generation as proposed in the model AIDE [42]. Hydrogen also reduces the formation energy of kink pairs at dislocations [40,43] and thus increases their mobility which is a prerequisite of the HELP model [40].…”

Materials and Corrosion Trends in Offshore and Subsea Oil and Gas Production

“…[92][93][94][95] Challenges of small-scale testing Once the size of the specimen or the volume of the material is reduced, the most challenging task is to retain the H atoms in such small dimensions. Except for some special alloys and metals, 96,97 it is impossible to stop hydrogen outgassing from a small sample. Therefore, a microscale mechanical evaluation of the influence of H in mechanical properties should be combined with in situ H charging.…”

“…6, show that the required load for pop-in, i.e., homogeneous dislocation nucleation, is reduced in the presence of H. Additionally, the amount of the reduction in the pop-in load scales with the amount of hydrogen which is controlled by the applied electrochemical polarization. Per the defactant theory, [108][109][110][111] the decrease in the load required for dislocation nucleation can be related to the reduction in the dislocation line energy by H. 96,112,113 Hydrogen effects on crack propagation: microcantilever bending tests FIB cut micro-samples, loaded inside a nanoindenter equipped with special tips have traditionally been used to study size-effects in metals and alloys. [114][115][116][117][118] The possibility of in situ electrochemical H charging inside a nanoindenter provides a unique opportunity to perform such microscale experiments on Hcharged samples, Fig.…”