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

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.