Kinetics of the growth of helium bubbles at the grain boundaries. formation of the spatially inhomogeneous distribution of helium bubbles near the grain boundaries

Dislocations mediate hydrogen retention in tungsten

“…We used the kinetic rate theory method and couple 3D bulk and 1D dislocation diffusion modes (see e.g. [24,25]). The duration of the plasma impulse was 70 s and the surface temperature was 460 K. A typical retention profile obtained by nuclear reaction analysis (NRA) in such experiments shows that the H concentration drops sharply after several µm (see right handside Y -axis in figure 2).…”

Theoretical prediction and direct observation of dislocation-free zone formation near a grain boundary in austenitic stainless steel under electron irradiation

“…Such heterogeneous microstructural formation of defect clusters near a grain boundary is commonly understood in terms of the interrelation between the di usional process of supersaturated impurities or point defects, that is vacancies and interstitials, towards the grain-boundary sink and the microstructural evolution process there. An exceptional case is DFZ formation by deformation, which has been observed not near a grain boundary but in a matrix of metals during deformation followed by quenching or irradiation (Suzuki et al (1991) and reference therein).In spite of a large body of experimental evidence on DFZ relatively few extensive theoretical studies can be found in the literature (for example Ryazanov et al (1985)). The reason for this is that a heterogeneous microstructural treatment in a theoretical model such as the di usional rate equation model, becomes fairly complex to solve dynamically, compared with a homogeneous microstructural study.…”

“…In spite of a large body of experimental evidence on DFZ relatively few extensive theoretical studies can be found in the literature (for example Ryazanov et al (1985)). The reason for this is that a heterogeneous microstructural treatment in a theoretical model such as the di usional rate equation model, becomes fairly complex to solve dynamically, compared with a homogeneous microstructural study.…”

“…INTRODUCTION A defect-free zone (DFZ) is known to occur near a grain boundary in metals. Some examples are the formation of a precipitation-free zone (PFZ) of a so-called denuded zone under thermal ageing (Nicholson 1968), of a void-free zone (Anthony 1972) and a helium-bubble-free zone (Ryazanov et al 1985) under irradiation. Such heterogeneous microstructural formation of defect clusters near a grain boundary is commonly understood in terms of the interrelation between the di usional process of supersaturated impurities or point defects, that is vacancies and interstitials, towards the grain-boundary sink and the microstructural evolution process there.…”

Cavity Evolution at Grain Boundaries as a Function of Radiation Damage and Thermal Conditions in Nanocrystalline Nickel

“…This is consistent with several other experimental studies which have observed a preferential accumulation of helium at grain boundaries in nickel. [23][24][25] When the nickel sample was then self-ion irradiated, the resulting irradiationinduced vacancies formed visible cavity structures, particularly in areas where there was already a high density of helium, such as the grain boundaries.…”