Tensile properties and microstructure of helium implanted EUROFER ODS

To study the effect of helium (He) on tensile properties and microstructure of oxide dispersion strengthened EUROFER-ODS steel, flat tensile specimens were homogeneously implanted with 30 MeV α-particles at the NRC KI cyclotron up to 1000 appm He at 573 K and 773 K. High-resolution and energy-filtered transmission electron microscopy showed that partly coherent Y2O3 particles are strong trapping centers for diffusing He atoms (at least up to 773 K) in reduced activation ferritic/martensitic 9Cr-1WMnVTa-0.3Y2O3 steel. After 573 K and 773 K implantation the He bubbles or He filled voids have average diameters of 1.9 and 4.2 nm with concentrations about 8 × 1022 and 7 × 1022 m−3, respectively. Tensile testing after 573 K implantation revealed a uniform elongation of more than 10%, despite an irradiation induced hardening of about 250 MPa. The role that nanoscaled Y2O3 particles play in He distribution, tensile properties, and on the mitigation of He embrittlement are discussed.