Influence of Grain Boundary Structure on Bubble Formation Behaviour in Helium Implanted Copper

Helium accumulation in metals during irradiation – where do we stand?

“…It has indeed been demonstrated that the large variation in density and size of bubbles at different GBs observed in Cu implanted with He at 738 K may be correlated with the varying atomistic structures of the GBs, suggesting that this structure is important for the diffusivity of He along GBs [24].…”

Diffusion of He interstitial and di-He cluster at grain boundaries in α-Fe

“…In general, binding energy increases linearly with GB excess volume. However, the diffusion constant for He diffusion along an extended defect is expected to depend significantly on the type of extended sink (dislocations or GBs), which has been observed at different GBs in fcc Cu implanted with He [10]. The large variation in density and size of bubbles at different GBs may be correlated with the varying atomistic structures of the GBs, which suggests that the GB's structure is important for the diffusivity of He along GBs.…”

Formation, migration, and clustering of delocalized vacancies and interstitials at a solid-state semicoherent interface

“…In these cases, interactions of vacancies and interstitials with interfaces may be as important to a material's overall properties as point defects in the bulk. Some interfaces, such as coherent GBs, exhibit point defect behaviors not unlike those encountered in perfect crystals [6][7][8] . Point defects absorbed at some non-coherent interfaces, however, reconstruct into delocalized configurations that do not resemble conventional vacancies or interstitials [9][10][11][12][13] .…”

“…Diffusion is easy in all directions when the spacing between fast diffusion pathways becomes sufficiently small, explaining the loss of misorientation dependence above a certain misorientation. Highly coherent GBs that correspond to "special" misorientations and GB plane orientations 6,7 do not contain any high diffusivity pathways and therefore exhibit self and impuritiy diffusivities comparable to those in the adjoining crystals.…”