Study on Effects of Cu content on Microstructure and corrosion resistance of Zr-Nb alloys

Abstract

With the further development of nuclear power, the fuel burn-up continues to increase and the refueling cycle is extended, which puts forward higher requirements for the performance of fuel cladding materials. In this paper, Zr-Nb-0.1Fe-x (0.05%, 0.1%, 0.2%) Cu alloy samples were prepared by using the process route and process parameters of industrial production of zirconium alloy plates. The effects of Cu content on the microstructure of Zr-Nb alloy and the corrosion resistance in 18.6 MPa / 360 °C Li+B aqueous solution were studied by means of high-temperature autoclave simulation test, scanning electron microscope, transmission electron microscope, metallographic microscope, and XRD observation and analysis. The results show that Zr-Nb-0.1Fe-xCu alloy precipitates a large number of elliptical second-phase particles, mainly distributed in the crystal. With the increase of Cu content, the number of the second phase whose size is greater than 100 nm increases, the solid solubility of Cu in the alloy matrix of Zr-Nb-0.1Fe-xCu alloy is less than 0.1%, and the second phase of Zr-Nb-0.1Fe-0.05% Cu alloy is mainly β-Nb and Zr-Nb-0.1Fe compounds, Zr-Nb-0.1Fe - (0.1%, 0.2%) Cu alloy second phase is mainly a large amount of β-Nb and Zr-Nb-0.1Fe and a small amount of Zr Cu compounds. The corrosion resistance of Zr-1Nb-0.1Fe alloy can be improved by adding ≤ 0.2% Cu. After 434 d of corrosion, the oxide film was completely transformed from t-ZrO2 to m-ZrO2. The interface between the oxide film and metal was tightly bound, and there were transverse microcracks in the oxide film, but it did not fall off. When the content of Cu is 0.2%, the corrosion resistance is the best.