EFFECT OF Bi ADDITION ON THE CORROSION RESISTANCE OF Zr-lNb ALLOY IN DEIONIZED WATER AT 360 °C AND 18.6 MPa

Abstract

The effect of Bi contents on the corrosion resistance of Zr-1Nb-xBi (x=0.05—0.3, mass fraction, %) was investigated in deionized water at 360 and 18.6 MPa by autoclave tests. The results show that the corrosion resistance of Zr-1Nb alloy can be improved by adding Bi, and the more the Bi content is, the better the corrosion resistance is. TEM and EDS analyses on the microstructures of the alloys show that there are two types of second phase particles (SPPs), including ZrNbFe and β- Nb. The Bi contents have little effect on the type, size and amount of SPPs, 0.3%Bi can be completely dissolved in α-Zr matrix and has no influence on the solution content of Nb in α-Zr matrix. From the fracture and inner surface morphology of oxide films observed by SEM, it can be seen that the Bi dissolved in the α-Zr could noticeably slow down the microstructural evolution of oxide film, including the propagation of micro-cracks and the transformation from columnar grains to equiaxed grains in the oxide film.