Experimental determination of the critical cavity radius in Fe-10% Cr for ion irradiation

Transmission electron microscopy was used to obtain a value for the critical radius for ion bombardments of the ferritic alloy Fe-10% Cr. Microstructural examinations were performed with JEM 120 and JEM 120 CX transmission electron microscopes (TEM). For observation of magnetic specimens, the JEM 120 C TEM was equipped with an AMG objective lens pole piece. Specimens were implanted with 300 appm followed by a 2 h heat treatment at 1000 K. This procedure established a population of small helium bubbles in the specimens. The specimens were then irradiated at 850 K with 4 MeV Fe++ ions to a damage level of 30 dpa. The heavy ion damage caused the formation of a cavity distribution consisting of a population of large cavities (av diam, anti d, 15.2 nm) and a population of small cavities (av diam 2.3 mm). Histograms of the cavity diameters for each population are shown. The small cavities constituted approximately 98% of the total cavity concentration. 2 references, 1 figure