Changes in Mechanical Properties of High-Purity V-4Cr-4Ti-Si, Al, Y Alloys after Neutron Irradiation at Relatively Low Temperatures

Abstract

Mechanical properties after neutron irradiation of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y and V-4Cr-4Ti-0.1Si-0.1Al-0.3Y alloys (nominal weight percentage) were studied. Neutron irradiation was carried out at 290°C to 8×1022 n/m2 (E>1 MeV, about 0.014 dpa) in the Japan Materials Testing Reactor (JMTR). Tensile tests were carried out using miniaturized specimens at ambient temperature and irradiation temperature. Charpy impact tests were conducted at temperatures from -196 to 0°C using an instrumented machine. There is little difference in tensile properties after neutron irradiation between the two alloys. Increase in yield stress was relatively small (∼100 MPa), and uniform elongation remained more than 10%. Because of a low concentration of interstitial impurities, good tensile properties could be retained even after neutron irradiation at 290°C. Ductile-to-brittle transition temperature (DBTT) of V-4Cr-4Ti-0.1Si-0.1Al-0.1Y alloys hardly changed, whereas absorbed energy was slightly reduced after neutron irradiation.

Evaluation of irradiation hardening of ion-irradiated V–4Cr–4Ti and V–4Cr–4Ti–0.15Y alloys by nanoindentation techniques

“…Y addition has little effect on irradiation hardening at 473 K. Watanabe et al [17] reported that dislocation loops were formed and no irradiation-induced Ti-CON precipitates after 2.4 MeV Cu 2+ ion-irradiation at 473 K to 0.25 dpa. Y addition suppressed irradiation-induced precipitation due to the reduction in interstitial impurities (so-called scavenging effect) and then improved ductility after neutron-irradiation [3][4][5]. Therefore, the scavenging effect of Y addition on the improvement of irradiation hardening is significant only in the temperature range where irradiation-induced precipitates are dominant, and is limited above the temperature between 200 and 400 o C.…”

“…In order to improve the irradiation embrittlement, yttrium (Y) was added to reduce the interstitial oxygen due to the formation of Y2O3. It has been reported that Y addition was effective to improve ductility after neutron-irradiation [3,4], while neutron-irradiation data are too few to prove how much Y addition is effective in irradiation condition of lower temperature region and of high-dose [5]. The effect of Y addition on irradiation hardening in lower temperature region and at high-dose was still unsolved.…”

Moderation of Negative Oxygen Effects by Small Yttrium Addition to Low Activation Vanadium Alloys

“…It has been reported that small addition of yttrium (Y) was effective to reduce oxygen impurity and improve ductility after neutron irradiation without severe degradation of low-temperature impact properties. [2][3][4][5] Y addition, on the other hand, can also degrade hightemperature strength, because Y could scavenge solute oxygen, which is a strong hardening agent in vanadium alloys, by a formation of Y 2 O 3 (Ref. 2).…”