Positron Annihilation Spectroscopy Characterization of Formation of Helium/Hydrogen-Vacancy Nano-Clusters in FeCr Alloy

Abstract

In the present work, Fe9Cr model alloy was implanted with 100 keV He and 60 keV H ions at room temperature. Positron annihilation Doppler broadening spectroscopy was employed to detect (H, He)-V complexes with open volume in the irradiated specimens. The results show that the positron is sensitive to the relative position of the gas atoms decorating the open volume; i.e., to the configuration of the (H, He)-V complexes. The formation of H-vacancy clusters after H implantation and a large number of vacancies can be retained after H-V decomposes at room temperature. For the pre-implanted He situation (He + H), He-vacancy clusters are formed in advance and the post-implanted H introduces a large number of vacancies and decomposable H-vacancy clusters. The He-vacancy clusters forming in advance may recombine with vacancies and H atoms to form stable He-vacancy clusters and a small amount of He-H-V complex.

Effects of He-D Interaction on Irradiation-Induced Swelling in Fe9Cr Alloys

“…The W parameter of the high-dose (5 × 10 16 He + /cm 2 ) irradiated sample has a sudden increase at a depth of 62 nm. We speculated that this may be due to the accumulation of helium atoms in the defects caused by the irradiation and the formation of bubbles [24,[29][30][31]. For the sample irradiated by helium ions, on the one hand, the concentration of helium atoms increases, and on the other hand, vacancies are also increased.…”