α′ formation kinetics and radiation induced segregation in neutron irradiated 14YWT nanostructured ferritic alloys

Abstract

Nanostructured ferritic alloys are considered as candidates for structural components in advanced nuclear reactors due to a high density of nano-oxides (NOs) and ultrafine grain sizes. However, bimodal grain size distribution results in inhomogeneous NO distribution, or vice versa. Here, we report that density of NOs in small grains (<0.5 µm) is high while there are almost no NOs inside the large grains (>2 µm) before and after irradiation. After 6 dpa neutron irradiation at 385–430 °C, α′ precipitation has been observed in these alloys; however, their size and number densities vary considerably in small and large grains. In this study, we have investigated the precipitation kinetics of α′ particles based on the sink density, using both transmission electron microscopy and kinetic Monte Carlo simulations. It has been found that in the presence of a low sink density, α′ particles form and grow faster due to the existence of a larger defect density in the matrix. On the other hand, while α′ particles form far away from the sink interface when the sink size is small, Cr starts to segregate at the sink interface with the increase in the sink size. Additionally, grain boundary characteristics are found to determine the radiation-induced segregation of Cr.

Intergranular corrosion behavior of low-chromium ferritic stainless steel without Cr-carbide precipitation after aging

“…J o u r n a l P r e -p r o o f 4 Recently, the radiation-induced segregation or depletion of Cr at grain boundaries in nuclear materials of ferritic and austenitic stainless steels have generated considerable research interest [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. It was reported by Marquis et al that the radiation-induced depletion of Cr in the ferritic stainless steels is observed by atom probe tomography (APT) when the grain boundaries are segregated with Cr and C in the absence of Cr-carbide phase [21][22][23][24].…”

Effect of High-Density Nanoparticles on Recrystallization and Texture Evolution in Ferritic Alloys

“…The FeCrAl alloy has a low fraction of second-phase particles having sizes ranging between~100 nm and~3 µm. On the other hand, 14YWT alloys have a high density (~6 × 10 23 m −3 ) of NO (Y-Ti-O) particles [18,[20][21][22]. The red arrows in these figures indicate the second-phase particles.…”

Irradiation stability and induced ferromagnetism in a nanocrystalline CoCrCuFeNi highly-concentrated alloy

“…[16][17][18][19][20][21][22] A particular field of technology where the potential application of nanocrystalline alloys has been under active consideration is in the selection of appropriate structural materials for the next generation of fission and fusion reactors, by mitigating the generation and by controlling the diffusion of crystal defects at the nanoscale. [23][24][25][26][27][28][29][30][31] An increased density of grain boundaries acting as active sinks for crystalline defects produced from energetic collisions has been recently reported to be the main reason of enhanced radiation resistance of many metals and alloys when compared with their coarse-grained alloy counterparts. [26][27][28] The major challenge for application of nanocrystalline materials in extreme environments remains to prevent the manifestation of degradation mechanisms resulting in microstructural instabilities such as grain growth 24,26,[30][31][32][33][34][35][36] and phase transformations.…”