Correlation Between Microstructure and Corrosion Behavior of Zr-0.8Sn-1Nb-0.3Fe Alloy

Zr-0.8Sn-1Nb-0.3Fe zirconium alloy sheets were prepared by different heat treatment processes. Then OM and TEM were used to analyze the microstructure of the samples, and static autoclave tests were carried out in 360 ºC/18.6 MPa/0.01 mol/L LiOH solution and 400 ºC/10.3 MPa superheated steam to investigate the corrosion behavior. The results show that the second phase particles (SPPs) are mainly C14 type Zr(Nb, Fe)2 with a HCP structure, and the uniformity of SPPs distribution gradually becomes worse when the hot-rolling temperature increases from 600 to 700 ºC. Aging treatment before hot-rolling not only improves the uniformity of SPPs distribution, but also promotes the diffusion of Nb, which increases the amount of βNb SPPs. Extension of final annealing time has little influence on size and distribution of the SPPs, but increases the Nb/Fe ratio in the SPPs. After long time corrosion tests, the corrosion resistance becomes worse when the hot-rolling temperature increases in both corrosion conditions. Aging treatment before hot-rolling can increase the corrosion resistance. Extension of final annealing time can also increase the corrosion resistance in LiOH solution, but decrease the corrosion resistance in superheated steam. The relationship between microstructure and corrosion resistance was discussed, and the size, distribution and the Nb content of SPPs are considered to be the main reason for the difference of the corrosion resistance of Zr-Sn-Nb-Fe zirconium alloys. © 2018, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.