In-situ 3D observation of hydrogen-assisted particle damage behavior in 7075 Al alloy by synchrotron X-ray tomography

Switching nanoprecipitates to resist hydrogen embrittlement in high-strength aluminum alloys

“…Nonetheless, we reasonably expect that the T-phase nanoprecipitates remain effective in hydrogen trapping even in the nanoscale highly stressed regions. Unlike the plate-shaped η phase and coarse intermetallic particles (such as the previously reported Fe-rich 30 and Mn-rich 25 particles, also shown to be effective in hydrogen trapping), the small size and spherical shape of T precipitates endow them with low-stress localization at sharp edges and excellent dynamic hydrogen trapping capacity in a transient hydrogen diffusion scenario. In the absence of neighboring voids, the hydrogen trapping effect in the T phase leads to a 2–3 orders of magnitude reduction in the hydrogen concentrations at dislocations, GBs, and vacancies (Fig.…”

“…1g to i provide compositional evidence of the T phase (with a maximum Zn + Mg concentration close to 80 at.%) in HT material 28 . The increase in aging temperature did not significantly alter the precipitate size (with an average diameter lower than 7 nm in both), which enables evaluation of the HE sensitivities of these two materials with similar tensile strengths and precipitate coherency 29 , 30 , although some of the coarse η precipitates in HT material are semi-coherent (Supplementary Fig. 4 ).…”

“…In terms of vacancies, a large quantity of vacancies is generally considered to always be generated with the creation of dislocations, and vacancies occupied with a sufficiently high amount of hydrogen can favorably aggregate to form platelets on a specific crystallographic plane, acting as embryos for microvoids and cracks 5 . In terms of η phase precipitates, spontaneous debonding at the coherent η/Al interfaces (with a hydrogen binding energy of 0.3 eV) may also occur due to the stress-induced high hydrogen occupancy at the edge surfaces 11 , providing another likely pathway for HE, whereas no such phenomenon has been found at semi-coherent η/Al interfaces despite their high hydrogen trapping the energy of 0.56 eV 30 . All the processes occurring at dislocations, GBs, and coherent precipitate interfaces are expected to be suppressed by the strong hydrogen trapping effect of the T phase.…”

Influence of Hydrogen on the Damage Behavior of IMC Particles in Al–Zn–Mg–Cu Alloys

“…The damage behavior of Al 7 Cu 2 Fe particles was governed by the mechanical responses of the particles themselves and their vicinity, not by the influences of the hydrogen particles. These results are consistent with the A d v a n c e V i e w conclusions of a previous report that investigated the influence of hydrogen on the damage behavior of Al 7 Cu 2 Fe and Mg 2 Si particles in an A7075 alloy using projection-type synchrotron radiation X-ray CT. 30) No particle hydrogen embrittlement due to internal hydrogen was observed in Al 7 Cu 2 Fe. However, Al 7 Cu 2 Fe particles are intrinsically brittle, 31) and even if dispersed in the matrix to prevent hydrogen embrittlement, abundant voids are formed due to particle damage, resulting in premature fracture.…”

Suppression of Hydrogen Embrittlement due to Local Partitioning of Hydrogen to Dispersed Intermetallic Compound Particles in Al–Zn–Mg–Cu Alloys

“…Wang et al reported that hydrogen partition to the MgZn 2 precipitate is not suppressed in regions where Al 7 Cu 2 Fe particles are not present. 24) It is therefore necessary to investigate the effects of HE suppression by intermetallic compound (IMC) particles using different volume fractions and various hydrogen concentrations. In the present study, four-dimensional (i.e., time axis and Euclidean space) observation of HE behavior was performed in two AlZnMg alloys in which the hydrogen concentration and the particle density had been varied.…”