Effect of Fe on Microstructure and Corrosion Behavior in 400℃/10.3 MPa Superheated Steam of Zr-xFe(x=0.05, 0.2, 1.0) Alloys

A series of Zr-xFe(x=0.05, 0.2, 1.0, wt%) alloys were prepared by adding different contents of Fe to the pure Zr. The effect of Fe on the microstructure and corrosion behavior in 400 °C/10.3 MPa superheated steam of zirconium alloys were investigated. The microstructures of alloy matrix and oxide layer were characterized by scanning electron microscope and transmission electron microscope. The results show that the grain size of α-Zr matrix is obviously decreased by adding 0.05wt% Fe but remains nearly unchanged with a further increase in Fe content from 0.2wt% to 1.0wt%. Most of the Fe atoms in the zirconium alloys is found to precipitate as Zr3Fe secondary phase precipitates (SPPs). The SPP size increases with the increase of the Fe content, whereas its structure remains unchanged. Fe not only promotes the growth of columnar crystals in the oxide layer, but also inhibits the columnar-to-equiaxed transformation, giving rise to a good corrosion performance of Zr-xFe(x=0.05, 0.2, 1.0) alloys. Additionally, the corrosion resistance of Zr-xFe(x=0.05, 0.2, 1.0) alloys is increased by increasing the Fe content. The stress accumulated at the oxide/metal (O/M) interface plays a key role in the formation of sub-oxides in Zr-1.0Fe alloy during corrosion process, which can relieve the stress at the O/M interface, and thus largely improving the corrosion resistance by impeding the columnar-to-equiaxed transformation. © 2021, Science Press. All right reserved.