X-ray studies of nickel, steel - Kh16N15M3B and steel -Kh20N40M5B irradiated by helium ions

The effect of helium ion irradiation to the concentrations of 0.05, 0.15, 0.50 and 1.00 at.% He (with He+ ion energy up to 3.5 MeV) on the structure of recrystallized nickel, steel-Kh16N15M3B and steel-Kh20N40M5B is studied by means of X-ray analysis. It is shown that phase composition of irradiated samples does not exhibit any changes: the initial f.c.c. structure was preserved under all irradiations. The lattice spacing of irradiated samples is found to vary nonmonotonically depending on the concentration of injected helium. Experimental data on the effect of post-irradiation annealing are indicative of nonmonotonic variation of the lattice spacing depending on the annealing temperature as well. It is concluded that changes observed in the diffraction pattern for investigated samples under He+ ion irradiation are not due to radiation damages (interstices, vacancies, dislocation loops, stacking faults, etc.) but to accumulation and evolution of helium atoms in the matrix lattice