Behavior of ion-implanted helium in Ni as a function of alloying element concentration (Al or Ti) and irradiation conditions (at 20 or 750°C) have been investigated by means of thermal desorption spectrometry (TDS) and transmission electron microscopy (TEM).

Substitution elements in solid solution were demonstrated to have substantial influence on the evolution of implanted helium, shifting the TDS spectrum peaks to higher temperature region and increasing the quantity of helium remaining in the samples after long-time postirradiation annealing. TEM investigations showed that in the case of postirradiation annealing, helium bubbles are formed earlier in quenched alloys than in those annealed. In the high-temperature irradiated alloys, the bubbles formed are smaller in size and higher in density than in the case of postirradiation annealed samples irradiated at room temperature. Alloying elements reduce bubble diameter and increase bubble number density. This is especially typical for concentrations of alloying elements that exceed the ultimate solubility in nickel.