Rapid assessment of structural and compositional changes during early stages of zirconium alloy oxidation

Elizabeth J Kautz,Sten V M Lambeets,Kuo-Pin Tseng,Libor Kovarik,Daniel E Perea,Suntharampillai Thevuthasan,Yi-Sheng Liu,David Senor,Anil K Battu,Arun Devaraj,Daniel K Schreiber,Bharat Gwalani

doi:10.1038/s41529-020-00133-6

Abstract

A multimodal chemical imaging approach has been developed and applied to detail the dynamic, atomic-scale changes associated with oxidation of a zirconium alloy (Zircaloy-4). Scanning transmission electron microscopy, a gas-phase reactor chamber attached to an atom probe tomography instrument, and synchrotron-based X-ray absorption near-edge spectroscopy were employed to reveal morphology, composition, crystal, and electronic structure changes that occur during initial stages of oxidation at 300 °C. Oxidation was carried out in 10 mbar O2 gas for short exposure times of 1 and 5 min. A multilayered oxide film with a cubic ZrO adjacent to the oxide/metal interface, a nanoscopic transition region with a graded composition of ZrO2−x (where 0 < x < 1), and tetragonal ZrO2 in the outermost oxide were formed. Partitioning of the major alloying element (tin) to the oxide/metal interface and heterogeneously within the oxide accompanied the development of the layered oxide. Our work provides a rapid, high-throughput approach for detailed characterisation of initial stages of zirconium alloy oxidation at an accelerated time scale, with implications for several other alloy systems.

Highlights

Alloys applied in nuclear reactors[1,2], gas turbines[3,4], heterogeneous catalysis[5,6], automotive internal combustion engines[7], and electronic devices[8,9] are routinely exposed to high-temperature, corrosive, and oxidising environments
Characterising one or more oxides formed during the initial stages of oxidation is a significant challenge because oxidation of alloying elements is simultaneous with the nucleation and growth of metastable phases[10,11]
The native oxide formed on needle samples during atmospheric transfer from the focused ion beam (FIB) microscope to the atom probe tomography (APT) microscope (Fig. 1) had a stoichiometry close to that of Zr3O

Summary

Introduction

Alloys applied in nuclear reactors[1,2], gas turbines[3,4], heterogeneous catalysis[5,6], automotive internal combustion engines[7], and electronic devices[8,9] are routinely exposed to high-temperature, corrosive, and oxidising environments. Further development of the oxide film was studied by analysing the oxide layers after exposing the APT needle at 300 °C for 5 min at 10.35 mbar O2 (Fig. 3).

Results

Conclusion