Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Zr-4 coarse-grained specimens were corroded in static autoclave at 360 ℃, 18.6 MPa in 0.01 mol/L LiOH aqueous solution for 70 and 160 d exposure. EBSD, SEM and HRTEM were used to investigate the microstructures and crystal structures of oxide layers, and the relationships between the oxide thickness and the grain orientation of the metal matrix. The results showed that the oxide layers formed on the grain surfaces with the orientations nearby basal plane (0001) were thicker, and exhibited a prominent anisotropic for the oxide growth when Zr-4 specimens were corroded in LiOH aqueous solution for 160 d, but this was not the case for 70 d. The grains with the surface orientation nearby (0001), (1010) and (1120) were selected from the specimens corroded for 70 d to investigate the effect of metal grain orientation on the microstructure of oxide layers. The results showed that the crystal structure and microstructure of oxide layers formed on different metal grains were obviously different, and the scattering of m-ZrO2 columnar grain orientations in the oxide layers formed on near basal plane (0001) was wider than that on near prismatic plane (1010) and (1120). Besides the majority of m-ZrO2, c-ZrO2, t-ZrO2 and sub- oxide phase Zr3O were also detected at the oxide/metal interface, and it showed that the microstructure and crystal structure of oxide layers were very complex. The microstructural evolution of oxide layers will affect the diffusion of oxygen and subsequently the growth of oxide. Therefore, the microstructural evolution of oxide layers, which was affected by the different microstructure of oxide layers formed initially on grains and the water chemistry of corrosion tests, resulted in the anisotropic growth of oxide layers when Zr- 4 specimens were corroded in LiOH aqueous solution in subsequent corrosion tests.
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