Small-angle neutron scattering investigation of the nanostructure of ferritic-martensitic 12%-chromium steels

The nanostructure (nanoparticle distribution) of ferritic-martensitic 12%-chromium steels EK-181 (Fe–12Cr–2W–V–Ta–B) and ChS-139 (Fe–12Cr–2W–V–Ta–B–Nb–Mo) subjected to different modes of mechanical and heat treatments and neutron irradiation has been investigated using small-angle neutron scattering. The samples have been studied in the initial state and after neutron irradiation (IVV-2M reactor) at a temperature of 80$^\circ$C with fluences of 10$^{18}$, 10$^{19}$, and 5 $\cdot$ 10$^{19}$ cm$^{-2}$ ($E\ge$ 0.1 MeV). The nanostructure of the steels is characterized by precipitations of nanoparticles with two characteristic sizes of 1.0–1.5 and 7–8 nm. The dependence of the nanostructure parameters on the composition of the steels and on the conditions of heat treatment and irradiation has been discussed.