| Zirconium alloy which is often used as nuclear fuel cladding tube has a unique corrosion resistance and good mechanical properties. The zirconium alloy cladding tube in the fuel reactor core is exposed to long period of high temperature and high pressure, it suffers from not only by the role of mechanical force, as well as neutron irradiation damage, both the inside and outside of the cladding tube was damaged by corrosion substance, hydrogen embrittlement and so on. Thus the study of the microstructure and properties of zrconium alloy cladding tube has great meaning. At present the microstructure and properties of Zr-2, Zr-4 zirconium alloy cladding tubes have been studied broadly, but seldom about N18, domestic M5(GM5 for short)and France-made M5(FM5 for short) cladding tubes. In this paper, the tensile properties, blasting properties, corrosion resistance and microstructure of Zr-2, Zr-4, N18, GM5 and FM5 were studied systematicly, specifically focused on the Similarities and differences between GM5 and FM5, in order to provide a theoretical basis for the localization of nuclear fuel cladding tube. The results are as follows:(1) The metallographic microstructure shows that GM5 and FM5 zirconium alloy cladding tubes have fine grain sizes, the grain size of N18 zirconium alloy cladding tube is slightly larger. The grain uniformity of FM5 and N18 are better than that of GM5. the microstructure of the three kinds of materials are equiaxed grains and precipitation particles are distributed on the matrix, FM5 has few disloctions, GM5 has a large number of dislocation tangles, N18 also has few dislocations but large sizes.of precipitation particles.(2) The axial and ring hoop tensile properties of Zr-2, Zr-4, N18, GM5 and FM5 at room temperature and 400℃were studied, the results show that GM5 and FM5 cladding tubes has moderate strength, good plasticity. N18 and Zr-2 cladding tubes had slightly higher strength and lower plastic property. Zr-4 cladding tube has moderate plastic property, but lower strength.(3) The results of burst test on GM5 and FM5 cladding tubes at room temperature show that the bursting strength of GM5 cladding tube is equivalent to that of FM5 cladding tube. The bubble elongation of GM5 and FM5 cladding tubes has no significant differences.(4) The corrosion behavior of N18, GM5 and FM5 were studied at the condition of 400℃, 10.5MPa vapor water. The results show that the corrosion process is fast and linear initial at the first few hours, and then transfer to a slow parabolic corrosion stage, with the longer the corrosion time, the slower the corrosion rate. The corrosion layer is thin, the thickness of corrosion layer is only 0.22-0.24μm. The corrosion rates of the three kinds of cladding tubes and corrosion layer thickness had no significant differences.(5) The tensile fractures of the 5 kinds of zirconium alloy cladding tubes are gray fibrous fracture at the macro level, the fractures have a lot of plastic deformation, and the fracture type is ductile fracture. The burst fractures of GM5 and FM5 cladding tubes are the same, they have the same fracture type. The macroscopic fracture patterns are gray fibrous, micro-patterns are dimple-like, the breaking mechanisms are micro-aggregation, and the fracture type is also ductile fracture. |
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