Microstructure Evolution of Selected Ferriticmartensitic Steels under Dual-Beam Irradiation

Abstract

AbstractWe present experimental results on the microstructure evolution of dual-beam irradiated (300 keV heavy ions plus 15 keV helium ions) ferritic-martensitic steels (Manet, DIN 1.4926, F82H mod). The helium bubble morphology as well as microchemistry of the alloys are investigated by means of transmission electron microscopy and field-ion microscopy with atom probe. The alloys were irradiated to fluences up to 50 dpa and implanted with helium up to a concentration of 1 at.% at the temperatures of 723 K and 773 K. The damage and implantation rates variied from 2.5 · 10−3 dpa/s to 2.5·10−2 dpals and from 0.5 appmls to 5 appm/s, respectively. Size and number density of helium bubbles is found to be rate dependent. Smaller implantation rates produce larger helium bubbles and smaller bubble number densities. Regions of local enrichment of alloy elements, typically 5 nm in size, containing chromium (up to 40 at.%), silicon, and nickel are detected. Number densities of helium bubbles and of regions of chromium enrichments are comparable and lie between 1023/m3 and 1024/m3. Possible extrapolation of the present ion irradiations to spallation source and fusion reactor conditions is shortly adressed.