Irradiation creep and precipitation in a ferritic ODS steel under helium implantation

Ferritic oxide dispersion strengthened (ODS) steel, PM2000, has been homogeneously implanted with helium under uniaxial tensile stresses from 20 to 250 MPa to maximum doses of about 0.75 dpa (3000 ppm He) with displacement damage rates of 5.5 × 10−6 dpa/s at temperatures of 573, 673 and 773 K. Straining of a miniaturized dog-bone specimen under helium implantation was monitored by linear variable displacement transformer (LVDT) and meanwhile by their resistance also measured by four-pole technique. Creep compliance was almost constant at 5.7 × 10−6 dpa−1 MPa−1 for temperatures below 673 K and increased to 18 × 10−6 dpa−1 MPa−1 at 773 K. The resistivity of PM2000 samples decreased with dose and showed a tendency to saturation. Subsequent transmission electron microscopy observations indicated the formation of ordered Fe3−xCrxAl precipitates during implantation. Correlations between the microstructure and resistivity are discussed.