Significant Suppression of Helium Bubbles in Oxide Dispersion Strengthened FeCrAl Alloys Irradiated by High Concentration of Helium

Oxide dispersion strengthened (ODS) FeCrAl alloys were successfully fabricated by various mechanical alloying time (10h and 40h), combined with spark plasma sintering (SPS) technique. To understand their helium irradiation resistance, two kinds of ODS FeCrAl alloys were implanted with helium ions at 400 keV in the fluence of 1 x 10(21)/m(2) at 350 degrees C, 400 degrees C, and 450 degrees C to investigate the effect of high concentration helium on the materials in advanced nuclear reactors. The distributions of helium bubbles associated with the microstructural features were characterized by transmission electron microscope (TEM). The experimental results showed that both the helium bubble sizes and volume fractions increased with increasing the irradiation temperatures. The high sink strength of nano-oxides and small inter-oxides distance contributed to the good suppression of helium bubbles growth. In particular, we identified that the high-density nano-oxides with the small sizes (<10 nm) could sequester the helium into several (1-3) tiny bubbles to inhibit bubbles accumulating and coarsening both in elevated temperatures and high helium concentration. Additionally, grain boundaries demonstrated the weaker ability than nano-oxides to disperse helium bubbles, when compared helium irradiation resistance in ODS FeCrAl alloys and FeCrAl alloys. Eventually, ODS FeCrAl alloys in this study revealed the superior helium irradiation resistance than other studied alloys, making it promising to be one of the potential structural materials applicated in advanced nuclear reactors.