Features of Gas Porosity Formation Along Helium Ion Trajectories in Vanadium Alloys

The results of an investigation of the development of porosity and swelling in the alloys V–Cr, V–W, V–Ta, and V–W–Ta irradiated by 40 keV helium ions to fluence 5·10 20 m – 2 at 650°C are presented. The investigations were conducted by means of transmission electron microscopy along the travel path of ions; this afforded some idea about the total swelling of the samples and the character of the depth distribution of the porosity in the targets. It was found that the gas swelling in binary alloys is identical to within the measurement error. Multicomponent alloying is effective from the standpoint of the suppression of helium swelling – the ternary alloy V–1%W–1%Ta is subjected to significantly less helium swelling. It observed for the first time in experiments that the distribution and penetration depth of helium ions different significantly from the calculations, and the effect depends strongly on the chemical composition of the irradiated alloy. Among the alloying elements tantalum promotes deeper penetration of helium ions. In addition, the effect increases with increasing concentration of tantalum in the alloy: in the alloys V–1%Ta and V–2%Ta, pores were discovered at depth 450–500 and 850–900 nm, respectively, which is significantly greater than the computed travel distance of 48 keV helium ions in vanadium (~300 nm).