The influence of hydrogen on deformation and fracture processes in high-strength aluminum alloys

Stability and Elastic Properties of Hydrogen Loaded Ti(1-x)Al(x) Alloys: An ab Initio Study.

“…We conclude that the decrease of the shear modulus C 44 of Ti, which occurs only while hydrogen and aluminum are simultaneously present in the metal matrix, is closely related to the reduced mechanical strength of Til-xAl, systems upon hydrogen loading. This interpretation is also consistent with our result of Table I that This microscopic mechanism had originally been proposed by C. Beachem [37] to explain fracture of hydrogen-loaded steel under tensile stress, and has been more recently used to explain a similar behavior in other high-strength Al-based alloys [39]. In systems under 19 tensile stress, defects are often present near strain singular points such as crack tips.…”

“…The dynamics of the transgranular fracture, which is of main interest in this work, is primarily determined by the ease of Peierls relief and largescale dislocation motion, both crucially dependent on the potential-energy surfaces and the temperature-dependent mobility of defects (such as interstitial hydrogen) for the structures discussed above. Uncertainty about the atomic-scale processes linked with embrittlement results from the fact that whereas brittle fracture is typically linked to the inhibition of dislocation motion, processes such as the Hydrogen Enhanced Local Plasticity of a stable system can effectively masquerade as embrittlement on the macroscopic scale [37][38][39][40]. This latter process will be discussed in more detail below.…”

Contribution of Hydrogen Embrittlement to SCC Process in Excess Si Type Al-Mg-Si Alloys

“…As pointed out by them, because of the highly localized nature of ductile fracture, either increase or decrease in ductility (elongation or reduction of area) and either hardening or softening in flow stress can be observed when measured for a macroscopic specimen. By an in situ environmental-cell TEM deformation technique, they concluded that hydrogen enhanced dislocation mobility and reduced the flow stress for aluminum materials, 7000 series alloy 14) and high-purity aluminum.…”

“…That fracture process is a highly localized plastic failure resulted from stress-hydrogen-dislocation interactions, which is supported by some experimental evidence. 14,15) Then rightly, HRF is more suitable for general terms rather than HE, but the present paper is still described in terms of the latter according to custom.…”

Advances in Physical Metallurgy and Processing of Steels. Function of Hydrogen in Embrittlement of High-strength Steels.

“…42) Direct evidence for the enhancement of dislocation mobility associated with highly localized plasticity due to hydrogen has been accumulated by means of in situ transmission electron microscopy using iron 43,44) and fcc metals and alloys. [45][46][47][48] Based on these findings, a hydrogen enhanced localized plasticity (HELP) model has been proposed. 49,50) Systematic analyses showed that HELP is caused by the effect of hydrogen in solution on reducing interactions between dislocations and other elastic centers.…”