Dramatic reduction of void swelling by helium in ion-irradiated high purity α-iron

Effect of helium on void swelling was studied in high-purity alpha-iron, irradiated using energetic selfions to 157 displacements per atom (dpa) at 773 K, with and without helium co-implantation up to 17 atomic parts-per-million (appm) He/dpa. Helium is known to enhance cavity formation in metals in irradiation environments, leading to early void swelling onset. In this study, microstructure characterization by transmission electron microscopy revealed compelling evidence of dramatic swelling reduction by helium co-implantation, achieved primarily by cavity size reduction. A comprehensive understanding of helium induced cavity microstructure development is discussed using sink strength ratios of dislocations and cavities. [GRAPHICS] IMPACT STATEMENT Reduction of void swelling by helium co-implantation is reported, highlighting that it's not always true that swelling will be higher in metals when helium is present along with irradiation damage.