Effect of microstructure variation induced by processing on corrosion behavior of Zr-Sn-Nb alloy

In order to investigate the effect of microstructure variation induced by processing on corrosion behavior of zirconium alloys, Zr-Sn-Nb alloy original plates were processed by rolling and annealing, and the microstructure and corrosion behavior of both original plates and processed plates were analyzed. It was found that after the original plates were processed, the recrystallized microstructure in original plates was transformed to stress-relieved microstructure in processed plates, with second phase particles ripening. When exposed to pure water and water containing H₃BO₃ and LiOH, the original plates have better corrosion property than the processed plates, and the corrosion transition of the processed plates happened earlier than that of the original plates. The grain structure differences of original plates and processed plates have two aspects of influence on oxide cracking and corrosion transition. Firstly, there were more defects in processed plates which results in smaller grains and larger grain boundary areas in oxide. Secondly, the strength of processed plates is higher, and this will lead to less stress accommodation of the growing oxide by plastic deformation of the matrix, and higher stress in oxide layer formed during the corrosion process. Both factors caused more cracks in the oxide layer of processed plates, leading to earlier corrosion transition and decreasing corrosion property. Second phase particles and their surroundings are susceptible to cracks during corrosion process, and may become the original source of cracks. However, second phase particle ripening was not closely related to decreasing corrosion property of processed plates.