Effect of β-phase on the corrosion and oxide characteristics of Zr-xNb alloys

To investigate the effect of β-phase on the corrosion and oxide characteristics of Zr-xNb alloys, the corrosion and oxide characterization test were performed. The specimens have different Nb content in the range from 1 to 5wt.% which were heat-treated 570 .deg. C for 500 hours to get the α+βNb phase and at 640 .deg. C for 10 hours to get the α+βZr phase after β-quenching. The specimens were tested in water at 360 .deg. C and the oxide characteristics of corroded sample having equal thickness were investigated by using TEM and low-angle XRD. The corrosion behavior of Zr-xNb alloys affected by the formation of β phase. The corrosion resistance was reduced when the βNb phase was formed rather than βZr phase. From the oxide analysis, the βNb phase would stabilize the columnar structure and tetra-ZrO2, while the βZr phase would transfer the columnar into the equiaxed structure and accelerate the transformation from the tetra-ZrO2 to mono-ZrO2