Temperature dependence of He bubble evolution in UNS N10003 alloys under He ion irradiation

The effects of irradiation temperature on helium bubble evolution in UNS N10003 alloys were studied using 500 keV He ion irradiation at a dose of 2 × 1016 ions/cm2 from 650 to 850 °C. As the irradiation temperature increased, the density of the helium bubbles decreased and their size increased. Polyhedral bubbles were observed at 850 °C, and the non-spherical shapes of these bubbles reduced their surface energy. The densities and mean diameters of the bubbles at 650–850 °C show Arrhenius behaviors with activation energies of 1.06 ± 0.17 and 0.35 ± 0.02 eV, respectively. The activation energies indicate that the He bubble evolution at temperatures ranging from 650 to 850 °C is not only controlled by He diffusion via a self-interstitial/He replacement mechanism but is also affected by the migration and coalescence of He clusters or bubbles via surface diffusion. Furthermore, bubble-loop complexes were observed at 750 and 850 °C. With the temperature increasing, the helium bubbles prompted the growth of dislocation loops, suggesting that the interaction between the helium bubbles and the dislocation loops is dependent on the irradiation temperature.