Fracture Toughness and Hydrogen‐Assisted Crack Growth in Engineering Alloys

Stress corrosion cracking of several solution heat-treated Mg–X alloys

“…As a result, the crack propagated along the grain boundaries although some were not perpendicular to the load direction. The fractographic features of Mg0.1Zr and Mg1Mn were consistent with the mechanism of hydrogen enhanced decohesion [17][18][19], which was also consistent with the research of Stampella et al [41] who reported that SCC for larger grained magnesium SCC was mixed inter-granular and transgranular. The trans-granular features on the fracture surface of the DW specimens were also consistent with the mechanical overload rupture, which was the same as that in the air specimens.…”

“…The traces of micro-voids of region E in Fig. 10 indicated that the SCC mechanism of Mg5Zn was probably hydrogen enhanced localised plasticity [18,[20][21][22]. There were no micro-voids traces in the SCC region B and region C, which was probably that the micro-void was too small to be observed by SEM or the Mg5Zn cracked through another mechanism, such as hydrogen enhanced decohesion or delayed hydride cracking.…”

“…The hydrogen enhanced de-cohesion mechanism [18][19][20] proposes that hydrogen decreases the atomic bonding at the tip of the sharp crack tip, or several tens of nano-meters ahead of the crack, where the tensile stress is maximum, or at particlematrix interfaces ahead of the crack, where hydrogen accumulates by stress-assisted diffusion. Hydrogen enhanced de-cohesion leads to tensile separation of adjacent metal atoms, and does not require any plastic deformation.…”

Micro-Modelling Approach to Predict the Influence of Hydrogen Pressure on Short Crack Behaviour

“…An important part of the research has concentrated on the cohesion effect of hydrogen on steel notch toughness reduction. Although the effect of local hydrogen pressure alone on steel toughness is considered by Knott [5] to be of less significance, Interante and Pressouyre [6] demonstrated through development of hydrogen induced cracking model (HIC), and more recently, Bergmann, et al [7] showed, by using finite element analysis techniques, that the local pressure effect on steel toughness is strongly dependant of the hydrogen trap site geometry.…”

Effect of solution treatment on stress corrosion cracking behavior of an as-forged Mg-Zn-Y-Zr alloy

“…Thus, for Mg alloys, it is widely accepted that the SCC processes usually involve hydrogen embrittlement (HE) 16 17 18 21 22 , but the specific nature of the HE mechanism remains uncertain 20 . Several HE mechanisms have been proposed to explain the SCC behavior of Mg alloys, such as hydrogen enhanced de-cohesion (HEDE), hydrogen enhanced local plasticity (HELP), adsorption-induced dislocation emission (AIDE) and delayed hydride cracking (DHC) 23 24 25 26 27 28 29 30 31 32 . Detailed reviews of these mechanisms are provided elsewhere 16 33 34 35 36 37 .…”