TEM characterisation of heavy-ion irradiation damage in FeCr alloys

Heavy-ion damage in a series of FeCr binary alloys and pure Fe has been investigated by TEM. Specimens were irradiated in bulk with 1.5 MeV Fe+ ions at an irradiation temperature of 300 °C. A TEM specimen preparation technique has been developed to access the peak of the buried damage region. The damage took the form of dislocation loops with sizes ranging up to a few tens of nanometres. Loops with Burgers vectors of type b = <1 0 0> and b = ½<1 1 1> were both present in all the specimens, but the proportion of <1 0 0> loops was higher in FeCr alloys than in pure Fe. In Fe-8%Cr the loop number density was determined to be (1.6 ± 0.2) × 1021 m-2. Nature determinations showed that <1 0 0> loops in Fe-11Cr and ½<1 1 1> loops in Fe-8Cr were of interstitial type.