Influence of Nb concentration in the α-matrix on the corrosion behavior of Zr-xNb binary alloys

The influence of the Nb concentration in the α-matrix on the corrosion behavior of Zr-xNb (x=0-0.6 wt%) binary alloys was evaluated using a static autoclave in the temperature range from 300 to 500 °C. Corrosion tests and precipitate analysis of Zr-xNb binary alloys showed that corrosion resistance increased with the increase of the Nb concentration in the α-matrix, and the best corrosion resistance was obtained when the Nb concentration was nearly at its equilibrium solubility limit at all test temperatures. The alloys containing a higher Nb concentration than their equilibrium solubility also showed good corrosion resistance, which could be attributed mainly to the formation of Nb-precipitates, resulting in an equilibrium Nb concentration in the α-matrix. These results imply that the corrosion resistance of Nb-containing Zr-alloys can be controlled by the Nb concentration in the α-matrix rather than the Nb-precipitates.