Abstract
An investigation was carried out on the formation and recovery of radiation defects of iron whiskers irradiated by Rikkyo University reactor (TRIGA 11 type) and Kyoto University Reactor (KUR).
Iron whiskers produced by hydrogen reduction of liquid iron halide salt were irradiated to a fission neutron dose of-1016 n/cmm2 (>1.28 MeV) at 19±1°K and the electrical resistivity changes (Δρ) were measured during irradiation.
It was shown that Δρ was proportional to neutron dose (φt) in the present dose range, and the defect formation velocity (i. e. dΔρ/dφt) varied with direction of neutron incidence.
On the basis of the present study it is suggested that the direction dependence of (dΔρ/dφt) is due to that of threshold energy.
On the other hand some whiskers have been isochronally annealed after irradiation and mechanical properties, for instance upper yield stress, were measured using an Instron type tensil machine at -196°C.
Annealing after neutron irradiation was found to cause a softening effect on iron whiskers; the upper yield stress remained unchanged on annealing temperature up to 330°C and then recovered steadily until it returned to the unirradiated value at 500°C.
It is presumed that softening of iron whiskers is attributed to aggregation of point defects such as dislocation loops.
