Effect of solute atoms on swelling in Ni alloys and pure Ni under He+ ion irradiation

The effects of solute atoms on microstructural evolutions have been investigated using Ni alloys under 25 keV He+ irradiation at 500 °C. The specimens used were pure Ni, Ni–Si, Ni–Co, Ni–Cu, Ni–Mn and Ni–Pd alloys with different volume size factors. The high number densities of dislocation loops about 1.5×1022 m−3 were formed in the specimens irradiated to 1×1019 ions/m2, and they were approximately equivalent, except for Ni–Si. The mean size of loops tended to increase with the volume size factor of solute atoms. In a dose of 4×1020 ions/m2, the swelling was changed from 0.2% to 4.5%, depending on the volume size factors. The number densities of bubbles tended to increase with the absolute values of the volume size factor, and the swelling increased with the volume size factors. This suggests that the mobility of helium and vacancy atoms may be influenced by the interaction of solute atoms with them.