The cathodic charging of hydrogen into binary Ni 3Al and Ni 3Al with 0.52at.% B has been investigated by measuring the positron lifetime spectra. It is found that the alloys with hydrogen atoms initially migrated to the pre-existent defects result in the decrease of lifetime of positrons in the defects. With the increase of H-charging time

more hydrogen atoms are accumulated at the defects

subsequently forming the gaseous hydrogen molecules with high pressure to generate larger open-volume defects

thus increasing positrons’ lifetime. Hydrogen effects are weaker in Ni25;337;Al with 0.52at.% B as compared with those in binary Ni25;337;Al alloy

which indicates that the addition of B atoms could suppress hydrogen-harmful effect in Ni 3Al alloys.