Investigation on the oxidation characteristics of copper-added modified Zircaloy-4 alloys in pressurized water at 360°C

In order to assess the influence of copper addition on the oxidation behavior of modified Zircaloy-4 (Zry-4) alloys as well as Zr–Cu binary alloys, weight gain changes in a pressurized autoclave at 360°C were investigated. The copper content varied from 0.1 to 0.8 wt% for the binary alloys and changed from 0 to 0.5 wt% for the modified Zry-4 alloys. The optimum copper content for improved oxidation resistance turned out to be in the range 0.1–0.2 wt% from weight gain measurements; in the binary alloy, the weight gain generally decreased with decreasing Cu content from 0.8 to 0.2 wt% although 0.1 wt% Cu specimen showed higher weight gain than 0.2 wt% Cu specimen. This tendency was observed in the modified Zry-4 alloy showing the lowest weight gain at 0.1 wt% Cu content. To understand the microstructural influence on oxidation of the copper-added zirconium alloys, the effects of copper additions on the crystal structure of the oxide, second phase precipitates and microstructure of the metal matrix were studied.