Microstructure of V-4Cr-4Ti alloy after low-temperature irradiation by ions and neutrons.

摘要

Recent interest in the application of a V-4Cr-4Ti alloy in the ITER prompted an investigation of the effects of low-to-moderate temperature irradiation (less than 420 C) on the alloy's mechanical properties. Two sets of experiments were conducted. The effects of fast neutron irradiation to (approx-equal)4 dpa at 390 C were investigated in the X530 experiment in the EBR-II reactor. Irradiation with single (4.5-MeV Ni(sup 2)) and dual ion beams (350-keV He(sup +) simultaneously with 4.5-MeV Ni(sup 2)) complemented this study. TEM observations showed the formation of a high density of point-defect clusters and dislocation loops (less than nm diameter) distributed uniformly in both types of specimens. Mechanical property testing of neutron irradiated material showed embrittlement of the alloy. The deformed microstructure were examined by TEM to determine the causes of embrittlement and revealed dislocation channels propagating through the undeformed matrix. The channels are the sole slip paths and they cause early onset of necking and loss of work-hardening. Based on a review of the available literature, suggestions are made for further research of slip localization in V-4Cr-4Ti alloys.