The effect of final annealing after β-quenching on the corrosion resistance of Zircaloy-4 in lithiated water with 0.04 M LiOH

To further understand the effect of heat treatments on the corrosion resistance of Zircaloy-4, some specimens were treated by β-quenching at 1020 °C for 20 min and then annealing at 480–600 °C for 2–200 h. The specimens were corroded in lithiated water with 0.04 M LiOH at 360 °C/18.6 MPa. The microstructures of the specimens and the oxide films were observed by TEM and SEM. The results show that the β-quenched specimen with the cooling rate of 100 °C/s behaves the best corrosion resistance. After annealing at 480–600 °C, the corrosion resistance gets worse with increasing annealing temperature. The annealing time has little effect on the corrosion resistance for the specimens annealed at 480 and 540 °C after β-quenching. However, the corrosion resistance of the specimens annealed at 600 °C becomes worse with the increase of annealing time. The grain size of the oxide on the specimen with high Fe and Cr concentrations in α-Zr is coarser than that on the specimen with low Fe and Cr concentrations in α-Zr, and the pores and cracks are fewer in the oxide film on the former specimen than those on the latter specimen. This indicates that a suitable increase in Fe and Cr concentrations in α-Zr matrix is beneficial to retarding the microstructural evolution of oxide, thereby improving the corrosion resistance.