The Recovery of Gas-Vacancy-Complexes in Fe Irradiated with High Energy H or He Ions

Abstract

Isochronal annealing experiments for Fe irradiated with H or He ions were carried out to study interactions between gas atoms and vacancy clusters. The accelerating energy of H and He ions was 1.0 MeV and 3.3 MeV, respectively. The total dose was 1:0 Â 10 21 H ions/m 2 (0.2 dpa) and 9:6 Â 1019 He ions/m 2 (0.3 dpa), and the irradiation temperature was 300 C. Positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements were carried out after irradiation and annealing for 1 hour up to the complete recovery temperature. Microvoids were detected after H or He ion irradiation. The characteristic difference was mainly shown in the recovery of vacancy type defects.

Thermal helium desorption spectrometry of helium-implanted iron

“…Experimentally, nuclear reaction depth profiling [13], transmission electron microscopy [14], positron annihilation lifetime and coincidence Doppler broadening (CDB) techniques [15,16] have been used in addition to THDS [10,17,18] to study He migration and He-induced defect clusters in iron. In addition, resistivity recovery measurement has been used to study kinetics of defects in iron produced by electron irradiation [19].…”

Defect structures in nickel and SUS304SS formed by the collapse of cavitation bubbles

“…Positrons from Na-22 in metals with many defects do not migrate as long as in well-annealed metals. Therefore, it is even possible to measure the lifetime of defects distributed within 10 lm from the surface [13]. The lifetimes measured from the two surfaces were nearly the same, which indicated that the cavitation damage formed not only near the impact surface, but rather was homogeneously distributed over the 0.1-mm-thick specimen.…”

Post-implantation thermal desorption of helium from poly- and single-crystalline iron

“…High purity (99.94%) SC iron disks were provided by Dr S.A. Maloy at Los Alamos National Laboratory. Small specimens ($0.5-1 Â 2.5 Â 3.5 mm) were cut from the plates or disks, mechanically polished to 1 lm grade smoothness, and then commercially implanted at room temperature with 4 He ions at 5 or 10 keV to fluences of 10 14 or 10 15 He/cm 2 . The implantation flux was $7-10 Â 10 10 He/cm 2 s. Grain size of the PC specimens was determined to be on the order of 50 lm through optical microscopy observations.…”

“…On the average, 20 and 33 Frenkel pairs are generated per He ion for the two energies, respectively. These values correspond to a peak displacement damage of $85 and 75 mdpa, and a peak He concentration of 2830 and 1760 appm for the two energies, respectively, at a fluence of 10 15 He/cm 2 .…”

“…On the nano-, micro-or macro-scopic level, experiments using optical or electron microscopy, nuclear reaction depth profiling, positron annihilation spectroscopy, coincidence Doppler broadening, thermal desorption and other techniques have been conducted to analyze He behavior and the coupled He and defect evolution in BCC iron and ferritic alloys [13][14][15][16][17][18]. More recently, continuum rate-theory modeling [19] has been compared to isothermal He desorption from BCC iron to validate ab initio results.…”