Investigating the stability of second phase particles in Zr-Nb alloys under irradiation

Abstract

The stability of the β-Nb Second Phase Particles (SPPs) in two types of Zr-Nb alloys (recrystallised Zr-1.0Nb and Zr-2.5Nb) was studied by in-situ heavy ion irradiation in a transmission electron microscope (TEM), combined with ex-situ analysis by energy dispersive x-ray spectroscopy (EDX). TEM thin foils were irradiated by 1 MeV Kr + ions at four different temperatures from 50 K to 873 K, and by 350 keV Kr + ions at different doses up to 39dpa. The change in size of individual β-Nb SPPs has been measured quantitatively, and the degradation mechanisms under irradiation at different temperatures discussed. It has been shown that the Nb redistribution between the SPPs and the Zr matrix is governed both by radiation induced mixing and local diffusion in the surrounding Zr matrix. Under the radiation conditions reported in this study, the β-Nb SPPs have shown remarkably stability against irradiation, and the extent of Nb redistribution between the SPPs and Zr matrix is very limited under all experimental conditions.

On the depth resolution of transmission Kikuchi diffraction (TKD) analysis

“…1 In-chamber camera view and schematic of on-axis TKD setup These particular Zr alloy samples were selected for study because they have very well defined microstructure containing second phase particles (SPPs) of a convenient size for these experiments. The final annealing step of the Zr-Nb sample at 560 °C leads to the formation of recrystallized α-Zr grains with the Nb mostly in solid solution and small Nb-containing particles that are generally spherical with an average diameter ~50 nm [22]. With a typical sample thickness of ~80 nm, some particles will be fully embedded inside the foil while the others may lie closer to one surface than the other and indeed may be truncated by the foil surface.…”

Understanding the Anomalous Short-Range Spatial Correlation Of Fe and Sn in Neutron-Irradiated Zr Alloys

“…The spatial relationship between solute elements in other neutron-irradiated Zr-based alloys (e.g. ZIRLO) has also been characterised using APT and these results will be compared to data from TEM studies [5]. The relationship between the nano-structural evolution and changes in the macroscopic properties of the alloys will be also discussed, alongside how this information can be used to validate or improve models within the community.…”

In-situ TEM study of irradiation-induced damage mechanisms in monoclinic-ZrO2

“…Figure 1 shows an example of a TEM foil prepared following these procedures. The improved specimen geometry stability allows a single specimen to be transported without risk of damage, and to be characterized by a combination of techniques, in-situ TEM, STEM/EDX, TKD and even NanoSIMS [54], to correlate observations of dynamic irradiation-damage processes with the irradiation-induced evolution of local crystallographic orientation and micro-chemistry in exactly the same region.…”