Research Of Corrosion Properties Of Nanocrystalline Zircaloy-4

It is certainly that nano-materials will have an attractive application prospects because of their outstanding properties, but the corrosion resistance maybe is the negative factor. At present investigations, the impact of surface nanocrystallined zircaloy on corrosion resistance is contradictory; no coincident opinion can be drawn. Therefore, revealed the corrosion mechanism, by studying the corrosion properties of surface nanocrystallined zircaloy, can provide experimental basis for optimizing of existing alloys and developing of novel alloys.One side of the simple was subjected to high-speed shot preening treatment in order to achieve a surface nanocrystallization structure in a certain depth. The oxide films of nanocrystallization Zircaloy-4 alloy in autoclave at 673K/10.3MPa steam have been observed by XRD,SEM,EDS,TEM, respectively in this paper. We draw conclusions as following:(1) Results of 160 days corrosion test under the 673K/10.3MPa condition show that the weight gain of nanostructure Zircaloy-4 is less than that of traditional structure, which indicate that nanostructure Zircaloy-4 has a better corrosion resistance.(2) The M/O interface of nanostructure Zircaloy-4 is more regular and smoother, which imply that, no or less clusters of pores develop in nanostructure.(3) The absence of Oxygen-rich area at the M/O interface of nanostructure Zircaloy-4, indicates that the corrosion process is lag of the traditional structure Zircaloy-4(4) The result of TEM observation indicates that t-ZrO₂ formed as a protected coating at the M/O interface in nanostructure zircaloy-4Experimental evidences indicated that the nanocrystalline zircaloy-4 could delay the transition of the corrosion. Simultaneously, the metal/oxide interface of nanostructure Zircaloy-4 was more regular and glossy than that of coarse-grain structure Zircaloy-4. Furthermore, many equiaxed grains were discovered in the oxide films formed on the nanostructure basis, which indicated that nanostructure Zircaloy-4 had a better corrosion resistance. This paper showed the corrosion resistance improvement of nanocrystallization Zircaloy-4 alloy had relation with the percentage of tetragonal-Zirconia, the stress of tetragonal-Zirconia and the high compressed stress of oxide film. However about the corrosion resistance mechanism of nanocrystallizaion Zircaloy-4 alloy should be researched and discussed in the further.