Helium production and precipitates in neutron-irradiated Al-Li and Al-Mg-Li alloys

Al-Li and Al-Mg-Li alloys were neutron-irradiated in JOYO, JMTR and RTNS-II with different types of energy spectra. Transmission electron microscopy (TEM) was carried out on as-irradiated specimens and on those after isothermal annealing at 400-degrees-C. From TEM observations, it was confirmed that He production by transmutation and the coagulation of He atoms after the annealing depend on the neutron energy spectra used for the irradiation. It was also elucidated that the addition of Mg to Al-Li alloys strongly suppresses the growth of He bubbles. Interrelations among precipitates, vacancies, He atoms and Li atoms were investigated, obtaining a reasonable coincidence between amounts.