The temperature dependence of the damage microstructures in neutron-irradiated vanadium

Abstract

Vanadium and vanadium with boron carbide additions (V-B 4C) were irradiated to ~1 dpa in the Oak Ridge Research Reactor at controlled temperatures ranging from 455 to 925 K. The V-B 4C alloy was enriched in 10B, which produced ~3900 at. ppm helium. In the vanadium specimens, the dislocation microstructures varied from clusters of small (< 50 nm diam) dislocation loops (455 to 625 K) to larger, homogeneously distributed loops at higher temperatures. Their Burgers vectors were a/2〈111〉. The V-B 4C specimens contained only tangled dislocation segments. Cavities were observed in all specimens. The cavity concentration decreased and the average diameter increased with increasing irradiation temperature. At 725 K, the maximum swelling was observed in both the vanadium (0.1%) and V-B 4C (1.4%). At comparable temperatures the cavities in the V-B 4C specimens were smaller and more numerous than those in the vanadium specimens. Helium bubbles were found on the grain boundaries in all of the V-B 4C specimens.