Evaluation of hardening behavior under synergistic interaction of He and subsequent H ions irradiation in vanadium alloys

Helium and hydrogen synergy effect on irradiation hardening in V-4Cr-4Ti alloys was investigated. The samples were irradiated helium or helium + hydrogen ions at RT (room temperature) and 300°C. Transmission electron microscopy (TEM) and nano-indentation test were used to investigate the defects and hardness evolution induced by ion irradiation, respectively. The curves for irradiation induced hardness have been analyzed by indentation size effect (ISE) and soft substrate effect (SSE) on the basis of Nix-Gao model and Kasada's method. Point defects appeared after irradiation at RT and dislocation loops and bubbles observed after irradiation at 300°C were responsible for hardening. The hardness after He + H ions irradiation at RT increased comparison with that of He irradiation samples at RT and 300°C because the synergistic interaction of pre-implanted He, subsequent H and the irradiation-induced defects may affect the evolution of hardening. Bulk hardness could be evaluated by least square method. Besides ISE, SSE was observed in sample after irradiated He + H at 300°C.