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Abstract

It has been reported that corrosion kinetics transition phenomenon in Zr-Nb-Fe alloys is triggered by lateral cracks in the oxide film. To further investigate the mechanism of this phenomenon, four Zr-Nb-Fe alloys with distinct chemical compositions were prepared via conventional rolling/annealing process and second �²-quenching/low temperature final annealing process. Scanning electron microscope, transmission electron microscope, nano-indentation and autoclave corrosion tests were jointly carried out to characterize in detail the microstructural features and mechanical properties of alloys and oxide film formed in the corrosion. The results indicate that it takes more time for the occurrence of corrosion kinetics transition phenomenon with the increase of the alloy strength. However, if the alloys with different composition have almost the same strength, the corrosion kinetics transition phenomenon takes place earlier when the oxide film has lower hardness. The reasons for the above results can be attributed to the fact that lateral cracks are presented in the oxide film above the sharp crests of undulations of oxide film and metal interface before transition, which results from the deformation of matrix. The alloy with higher strength can resist the deformation of matrix and thus retard the evolution of undulated interface. Then, the lateral cracks in oxide film appear later. However, the oxide film with lower hardness is easier to be cracked since it may exist more flaws, such as pores and micro-cracks.

Biography

Email: luweijie@sjtu.edu.cn