Effect of microstructure on corrosion characteristics of Zr-5Nb alloy

For a better understanding of the correlation between a corrosion and a microstructure, it is necessary to study a phase transformation with an annealing condition for Zr-Nb alloy. Zr-5wt.%Nb alloy with different phase characteristics was prepared with various annealing conditions. A microstructural study and corrosion test were performed to investigate the effect of a phase such as the phase type, fraction, and size on corrosion. The corrosion behavior of the Zr-5Nb alloy was very sensitive to the annealing condition, which affected the formation of the beta-phases (beta-Nb or beta-Zr). The corrosion rate of the Zr-5Nb alloy annealed at 500 degrees C with the formation of the beta-Nb phase was lower than that of the Zr-5Nb alloy annealed from 600 to 800 degrees C with the formation of the beta-Zr phase. The highest corrosion rate was observed for the beta-quenched Zr-5Nb alloy. After a consideration of the corrosion rate and microstructure of the Zr-5Nb alloy, the corrosion resistance of that alloy was improved due to the formation of a small sized beta-Nb phase which could be controlled by the annealing condition.