EFFECTS OF NEUTRON IRRADIATION ON THE PROPERTIES OF VANADIUM-IRON ALLOYS

Abstract

The paper presents the results of testing samples of V+(0 – 5,0 at.% Fe) alloys irradiated with neutrons to 1,4 and 2,8 dpa at a temperature of 350 to 450°C, obtained using a set of experimental techniques: determination of density d, electrical resistivity ρ at indoor and liquid nitrogen temperatures, and internal friction at up to 600 °C . Concentration dependences d ~ f(CFe) and ρ ~ f(CFe) have been plotted. The neutron irradiation to 1,4 dpa at a temperature of 350 to 450°C involves breakdown of the solid interstitial solution in unalloyed V, its stabilization in alloys, breakdown of the solid substitution solution, and segregation of Fe atoms at discharge points. It has been shown that, unlike unalloyed vanadium, the density of alloys in the concentration range of 0,65 to 3,30 at.% of Fe increases by about 0,16 to 0,41% as a result of irradiation to 1,4 dpa. Concentration dependences were obtained on the V+(0 – 5 at.% Fe) samples irradiated with neutrons to 2,8 dpa at temperatures of 350 to 450°C for density d: linear dependences of density d ~ f(CFe) in non-irradiated samples become power-law after irradiation (to 2,8 dpa) and are described by the expressions dnon-ir = 6,1094 + 0,0223•CFe, g/cm3, dir = 6,073 + 0,07179•CFe – 0,0345•(CFe)2 + 0,0058•(CFe)3, g/cm3. Vanadium and alloys with 0,5 and 2 at.% of Fe after irradiation to 2,8 dpa swell by 0,7% at most, as the density of the V+5 at.% Fe alloy increases with irradiated at 1,25%, which is explained by the phase instability of the alloy and the possible formation of Fe atoms in the local enrichment areas. The electrical resistivity (at 298 K and 77 K) of non-irradiated and irradiated V-Fe alloy samples, as a function of the Fe content, varies in a non-monotonic manner which is indicative of potential near ordering and/or stratification of the solid solution, this being also confirmed by internal friction data.