Shape, orientation relationships and interface structure of beta-Nb nano-particles in neutron irradiated zirconium alloy

Abstract

Under neutron irradiation, radiation enhanced beta-Nb nano-precipitates develop within the -grains of the Zr-Nb alloys. This radiation enhanced precipitation is of great interest since it may have some influence on the post-irradiation mechanical behavior of the material. In this paper the shape, the orientation relationship and the interface structure of such nano-particles are studied by means of both conventional and high-resolution transmission electron microscopy. The radiation damage was annealed out, thanks to a prior heat treatment and a creep test, in order to easily observe the beta-Nb nano-particles. The nano-particles exhibit a needle-like shape with a short thickness along the cdirection of 1.5 nm on average, a length and a width respectively of 6 nm and 3 nm, on average, in the basal plane. Using high-resolution TEM, a near Pitsch-Schrader orientation relationship is identified for a nano-particle. The interface atomic structure at various locations around the nano-particle has been accurately determined and an atomic model of the interface structure has been proposed.

APT and TEM study of behaviour of alloying elements in neutron-irradiated zirconium-based alloys

“…Similar to the Zircaloy-2 date above, Fe and Sn-rich regions have formed, whilst discrete Nb-rich precipitates have also formed in the Sn-rich planes. Similar Nb-rich precipitates have been observed in High Resolution Transmission Electron Micrographs from neutron-irradiated Zr-Nb alloys [8,27]. The Nb-rich nanoprecipitates in the low-Sn ZIRLO can just be resolved in the EDS maps in Figure 4 (c).…”

“…Accurate prediction of safe Zr-clad fuel rod lifetimes, and the design of novel Zr alloys to increase these lifetimes, relies upon a thorough understanding of the changes that these materials undergo as a result of exposure to the harsh environments experienced in reactor cores. A large body of work has been published on the generation of dislocation arrays under irradiation [7][8][9], and more recently on local chemical redistributions around these arrays, for instance the anti-correlation of Sn and Fe along the c-axis in Zircaloy-2 [9] and the formation of solute clusters on dislocation loops after irradiation [10][11][12]. Atomistic modelling indicates that Fe has a positive drag ratio with vacancies in Zr, whilst Sn has a negative drag ratio [13]; potentially explaining why Fe segregates to dislocation loops that act as sinks for vacancies.…”

Novel α + β Zr Alloys with Enhanced Strength

“…E110 alloy and a similar M5 alloy contain 1 wt% Materials 2021, 14, 418 2 of 12 of Nb, which is just at the α/α + β boundary of the Zr-Nb phase diagram [8]. These alloys may contain tiny Nb-rich β phase precipitates, depending on thermal treatment and/or neutron irradiation [9][10][11]. Intermetallic particles are present when a very low solubility of Fe, Cr and similar elements is exceeded [12], as e.g., in commercial E635 alloy (Zr-1Nb-0.3Fe-1.2Sn) [9].…”

Irradiation resistance of nanostructured interfaces in Zr–Nb metallic multilayers

“…These two stacking orientations have been observed experimentally in similar HCP-BCC Mg-Nb multilayers by Chen et al [14]. The third OR consists of 1 210 ð Þk 100 ð Þ and 1010 ½ k0 11 ½ orientations and is taken directly from high-resolution transmission electron microscopy (TEM) studies of Nb nanoprecipitates in Zr [23]. All three structured interfaces are illustrated in Fig.…”