Study on Microstructure of Oxide Film for New Zirconium Alloys

The microstructure of oxide film for new zirconium alloys was studied. The results show that the microstructure of oxide films is much alike from inner surface to outer surface for NZ2 and NZ8 alloys by different intermidiate annealling treatment. The effect of different annealling lies in that whether there are precipitates embedding in oxide, the higher the accumulative annealing parameters, the more the probability of precipitates embedding. The embedded precipitates promote oxide transition to monoclinal structure and promote cracking along the former alloys grain boundary. SEM shows that the oxide film grows in a inhomogeneous way. The film in the inner surface appears in morphology like Cauliflouer, which is realted to accelerating corrosion. The faster the corrosion, the bigger the "Cauliflower" in size is. The results obtained by this study comfirm that adopting low temperature working process can make further refining of precipitates size, and this is the effective way to improve corrosion resistance of new zirconium alloys.