Influence of hydrogen on the behavior of dislocations

Hydrogen Embrittlement as a Conspicuous Material Challenge─Comprehensive Review and Future Directions

“…(b) The influence of introduced H gas pressure on the dislocation velocity ( V (H 2 )) in the same material. Reprinted with permission from refs and . Copyright 1988, 2012 Elsevier.…”

“…519,521,617,623,626−628 The typical experimental procedure involves straining the thin-foil sample till crack propagates, after which H is introduced with either incremental straining or maintaining constant displacement. 617 In the former case of incremental straining, the crack propagation usually occurs at a high speed which renders the capture and interpretation of the dislocation activity near the crack tip difficult. As such, the acquired knowledge from these studies does not show too much progress in comparison to that based on post-mortem crack analysis.…”

“…The intricate nature of HE has consistently driven the demand for innovative experimental techniques, contributing significantly to advancements in the field. A typical example is the application of environmental TEM for the in situ probing of dislocation motion in the presence of H. , Such experimental practice, which dates back to the 1980s, has revealed a number of important observations that later served as key evidences for the operation of the HELP mechanism. , Traditional and still the most widely used experimental approaches for studying HE mechanism rely on post-mortem characterization on samples that are deformed or fractured in the presence of internal or external H. ,, This can provide important insights on the process of H-induced defects and damage evolution. Nonetheless, the dynamic nature of H interaction with defects and subsequent damage progression underscores the significance of in situ characterization techniques.…”

Monitoring Tensile Fatigue of Superelastic NiTi Wire in Liquids by Electrochemical Potential

“…In superelastically transforming NiTi, suppression of the transformation inevitably leads to the increase of the local stress, plasticity or possibly even to cracking. According to the literature [37], the effect of absorbed interstitial hydrogen on the kinetics of dislocation and transformation processes is confined to a narrow temperature and strain rate windows, outside of which, solute hydrogen can have very different, even opposite effects.…”

“…The wire was kept in the elongated state during the SEM observation. While the small oxide cracks (detail in the inset) which are homogeneously dispersed over the wire surface cannot be seen in low magnification, the longer/wider oxide cracks appearing preferentially at inclusions and/or notches are clearly visible the electrolytic route to find out that the adsorbed hydrogen brings about severe decrease of the strength [37,38] and leads to brittle fracture [38,41]. Particularly, they claimed that the hydrogen adsorption rate is much faster, when the NiTi is electrolytically hydrogenated while it transforms during cyclic mechanical loads [40], compared to the cases when it is stress free, under constant stress or cyclically loaded in elastic range.…”