Increasing the size of the interface zirconium oxide crystal can reduce the tetragonal phase fraction near the interface, so as to reduce the internal stress caused by the transition from tetragonal phase to monoclinic phase, and reduce the diffusion path of H and O in the oxide film. Controlling the texture can make the matrix orientation match with zirconia lattice as much as possible, and also be beneficial to improve the corrosion resistance [43]. The stability of the tetragonal phase is affected by many factors. The transition from the tetragonal phase to the monoclinic phase affects the microstructure of the oxide film, which is the main factor controlling the corrosion resistance of zirconium alloys.
The corrosion behavior of zirconium alloys is related to the structure, composition and heat treatment of zirconium alloys.
Zr-sn alloy has advantages of small size second phase against furunculosis corrosion and large size second phase against uniform corrosion. The uniform fine second phase corrosion resistance of Nb zirconium alloys is favorable.
When zirconium alloy is corroded in high temperature and high pressure water, the oxide film growth changes periodically and has layered structure. The growth of the oxide film is controlled by the stability of the tetragonal phase at the oxide film/metal interface. The stability of the tetragonal phase is affected by various factors such as the compressive stress inside the oxide film, the second phase, the grain size of zirconia and the texture of zirconium alloy, which is the dominant factor controlling the corrosion resistance of zirconium alloy.
The corrosion mechanism of zirconium alloy and its influencing factors are very complicated. In recent years, the zirconium alloy with better corrosion resistance than zr-4 has been developed through extensive research on the composition, processing technology and preparation technology of zirconium alloy at home and abroad. However, it is necessary to further study the law and mechanism of the influence of alloying elements on the corrosion performance of zirconium alloys, the concentration of solid solution elements in the alloy matrix, the influence of the size and distribution of the second phase on the corrosion resistance of zirconium alloys, the distribution characteristics of alloying elements on the metal-oxide film interface, the nucleation and growth mechanism of the oxide film, etc.
